90 ms·

Linus Torvalds: “Somebody is pushing complete garbage for unclear reasons.”

• DiabloD3 9y ago
  So are we going to unmerge this, and force Intel to fix this properly in microcode?
  • Valmar 9y ago
    Said current patches haven't been merged. Just posted to the mailing list for review. Retpolines for Spectre, and PTI for Meltdown, are still in the kernel. Linus doesn't have too much disagreement with them. It's the IBRS / IBPB code for Intel's CPUs that Linus has a problem with. Also, not everything can be mitigated in microcode, for many reasons, not all of which I understand myself. Sometimes, only a fundamental hardware-redesign can fix the issues proper.
    • Animats 9y ago
      Well, for one thing, modern CPUs aren't microcoded much. Real microcoded CPUs went out with the 1980s. The microcode in today's fast CPUs is mostly initialization, and maybe emulation support for some instructions nobody uses any more, like decimal arithmetic or 16-bit mode. The microcode can maybe turn some stuff off and tweak some tuning parameters. Anyone know what Intel's "fixes" really do?
      • StudentStuff 9y ago
        Wat? All the major hardware manufacturers from Intel to the hundreds of no name ARM licensees fix and cover up major issues in silicon with fixes in microcode (unless most chips from a particular mask/process are too screwed up, see Intel's 7nm process). Doing otherwise would throw the onus onto kernel maintainers for Windows, Linux, and the various BSD distros, and they don't want a crapton of one off fixes for the plethora of CPU errata that Intel and others patch in microcode.
      • Sephr 9y ago
        Microcode is a little more capable than that. See https://media.ccc.de/v/34c3-9058-everything_you_want_to_know_about_x86_microcode_but_might_have_been_afraid_to_ask https://media.ccc.de/v/34c3-9058-everything_you_want_to_know... Edit: s/Intel m/M/
        • peoplewindow 9y ago
          That talk is about AMD.
      • nabla9 9y ago
        All instructions that decode into more than four micro-ops still go trough microcode. Typically 5% of micro-ops are still coming from the microcode sequencer even in modern architectures. Compiler has large effect. Common operations like CALL and PUSH go trough microcode even in m64 but there are alternatives. Many floating point operations have assists. Nonoptimal memory alignment might go trough microcode.
• ramshanker 9y ago
  So, it means more delays in upstream patches.
  • mrmondo 9y ago
    Would you rather have the kernel filled with false or botched security?
  • Valmar 9y ago
    Retpoline and PTI patches are fine. IBRS and IBPB patches are what will be delayed and maybe never merged. Linus reckons that the Retpoline code will be quite sufficient.
• dotancohen 9y ago
  I must say that I'm really happy that Linux is taking a stance on this one. He doesn't care what the legal consequences to Intel are, he is pushing for a proper technical solution damned be the consequences.
  • smcleod 9y ago
    You’re not the only one, he may be brash at times but god damn we need him and maybe we need his brash anti-bullshit meter too.
    • ealexhudson 9y ago
      Being able to call out bullshit doesn't mean having to curse it out. All Linus needs to do is say something like "I don't understand why this is here, and I'm not merging it until I do", rather than "They do literally insane things. They do things that do not make sense". The latter is not a technical argument, and it doesn't provide accuracy or clarity about next steps. "So somebody isn't telling the truth here. Somebody is pushing complete garbage for unclear reasons" - maybe the patches are bad. Or maybe there is an undisclosed vulnerability (like https://skyfallattack.com/ https://skyfallattack.com/ ?) that needs this "garbage" to mitigate it, and no-one got Linus properly in the loop. If it's the latter, all this shouting and cursing about "They do things that do not make sense" has likely attracted the attention of people interested in such things...
      • bigato 9y ago
        > "I don't understand why this is here, and I'm not merging it until I do" This is not clear enough and could be interpreted as incompetence on the part of the speaker
        • ealexhudson 9y ago
          It turned out that Linus had confused "IBRS" and "IBPB". That seems to me that he didn't understand it. I'm not sure why saying "I don't understand this" would confer _incompetence_ rather than just not understanding. Understanding is easily gained with good communication. The original patch set clearly doesn't explain the point of the patches well, and everyone gets things wrong as well. There's no shame in saying "I don't understand this", it's not a final statement equivalent to "I will never be able to understand this".
• yborg 9y ago
  Run through the Linus drama filter, the only thing I get from this is "Linus doesn't like the Meltdown/Spectre patches'; Linus having issues with a patch is, well, not particularly newsworthy. Is there something more significant here than a bad first go at this?
  • awakeasleep 9y ago
    Thats a pretty superior attitude you're taking regarding a disagreement about which you admit you understand nothing
  • phamilton 9y ago
    > See the difference between IBRS_ALL and RDCL_NO. One implies Intel will fix something. The other does not. I think that's a pretty interesting claim on his part. I can't weigh in too much on the evidence to support this claim, but it's certainly more than just a rant it seems.
  • dmichulke 9y ago
    I interpreted it as: Intel isn't going to fix Specter in HW (as opposed to Meltdown) Instead, they do some crazy crazy black magic in the patches.
    • Valmar 9y ago
      Crazy black magic which is insane and completely unnecessary, according to Linus. Seems like Intel just wants to half-arse a solution.
    • silvestrov 9y ago
      I read it like: Intel will make a fix but the fix will be disabled by default as that results in the best performance numbers, those that will be reported in the media. When you want to use the CPU in the cloud, you have to enable the fix and get much lower performance. But nobody in the media will care about that as they have the nice performance numbers and therefore Intel don't care to implement a fix with high performance.
    • 9y ago
• trynewideas 9y ago
  FWIW, at least a small part of that email is due to a confusion between Intel acronyms: http://lkml.iu.edu/hypermail/linux/kernel/1801.2/04637.html http://lkml.iu.edu/hypermail/linux/kernel/1801.2/04637.html
  • swiley 9y ago
    It worries me that this isn't higher both here and on Reddit. I read through the rest of the email thread this morning and wanted to say something but I'm worried that I don't understand it well enough.
  • koheripbal 9y ago
    Agreed, but I don't think it changes the bulk of what he's talking about.
• mrmondo 9y ago
  I think we should count ourselves lucky we have someone so good at spotting bullsh*t like this - and isn’t afraid to call it out as they sees it. Intel & friends have absolutely disgusted me lately, it could be all to easy to settle for less based on their standards, but let’s not let them set the standard - they’ve shown they can’t be trusted with quality and when they fail - they can’t be trusted to be transparent or even take ownership of the problems they create.
  • integricho 9y ago
    Intel transformed from a technology company to a management company. That somewhat explains their highly unreasonable behavior.
    • Valmar 9y ago
      Management can seriously make or break a company in various ways. It sucks... :/
      • mrmondo 9y ago
        Could not agree more, unfortunately I’ve seen the latter more often than the former. When you find good management it is truly inspiring however.
        • mseebach 9y ago
          There's some bias to this, though. Good management is much more "everything and everybody just seemingly by if self seems to be more or less in the right place" and less "Steve Jobs screaming at everybody about rounded corners and then everybody realising five years later that this is actually a much bigger deal than everbody except Jobs saw at the time" -- in other words, pretty invisible.
          • prewett 9y ago
            I'm curious, how were the round corners important? I like them, and I buy his argument that nothing in the real world has sharp corners, but Android has had sharp corners forever. (I'm asking because I'd like to know the answer, not because I'm asserting the opposite.)
• dingo_bat 9y ago
  I'm going to be honest, I need an ELI5 here. I know what the meltdown/spectre issues are, and kinda understand what retpoline is.
  • Johnny555 9y ago
    Here's an explanation of retpoline: https://support.google.com/faqs/answer/7625886 https://support.google.com/faqs/answer/7625886 “Retpoline” sequences are a software construct which allow indirect branches to be isolated from speculative execution. This may be applied to protect sensitive binaries (such as operating system or hypervisor implementations) from branch target injection attacks against their indirect branches. The name “retpoline” is a portmanteau of “return” and “trampoline.” It is a trampoline construct constructed using return operations which also figuratively ensures that any associated speculative execution will “bounce” endlessly.
    • dingo_bat 9y ago
      Maybe I wasn't clear. Your explanation and the linked article is very informative, but I wanted to understand what's the "garbage" Linus is talking about. As I said, I do understand retpolines from a high level.
      • jpgvm 9y ago
        The garbage part is still somewhat beyond my understanding but as I see it he isn't so much talking about the decision to not disable insecure branch prediction by default but rather addressing some very weird behaviour the patches add to kernel entry/exit points. Namely writing to MSRs (Model Specific Registers). This seems non-sensical as the branch predictor shouldn't need screwing with at this stage because the kernel already has retpoline protection. So he is musing there is further ulterior motives here.. perhaps another vulnerability (beyond Meltdown/Spectre) they are getting out ahead of with these very peculiar changes. He is still ofcourse mad that they don't seem like they want to fix Spectre correctly but that seems tangential to how pissed he is that they are trying to get code merged that clearly does something other than just mitigate Spectre. Unfortunately this entire thread is derailed with garbage about how Linus talks, rather than the fact he thinks Intel is doing something really fucking dodgy here and we should all try work out what it is.
• mrmondo 9y ago
  In case it’s unclear to anyone, David Woodhouse (the person Linus is replying to / previous poster) works for Amazon and previously Intel[1] aka @dwmw2 on Twitter, ironically his twitter profile is: “Kernel hacker. Known to occasionally promote an attitude of violence towards complete morons.” *[1] Correction, I thought (as does Google) that he still worked at Intel, but it was pointed out that he now works at Amazon UK.
  • zootm 9y ago
    This isn't the case, he works for Amazon. Unless he also works for Intel but that seems unlikely. Edit: Just to make this clearer you can see his email in the Signed-off-by of the patch under discussion: https://lkml.org/lkml/2018/1/20/163 https://lkml.org/lkml/2018/1/20/163
    • mrmondo 9y ago
      Thanks for pointing that out - I was under the impression he still worked for intel, before commenting I checked and all the top Google results suggested as much, I’ve corrected my comment.
  • avree 9y ago
    Thanks for this, the beginning where he quotes himself threw me off.
    • mrmondo 9y ago
      No worries at all, mailing lists are a PITA to navigate at the best of times.
    • NamTaf 9y ago
      I, too, missed the double-indenting at the start and thought David was replying to Linus. Once I got to the textbook swearing I double-checked and figured it out.
  • mrmondo 9y ago
    * Principal Engineer - Amazon Web Services - Employed Oct 2016 – Present - Employment Duration 1 yr 4 mo * Intel Corporation - Linux Kernel Engineer - Employed Jun 2008 – Oct 2016 - Employment Duration 8 yrs 5 mos Source: LinkedIn - https://www.linkedin.com/in/dwmw2/ https://www.linkedin.com/in/dwmw2/ Note: Also, this is not and please do not turn this into a personal witch-hunt or anything like that, I am just adding context / clarification as to the mailing list thread.
• brunoqc 9y ago
  Why do people censor words like that? They are not fooling anyone.
  • onion2k 9y ago
    They are not fooling anyone. They are fooling the content filters some corporate services use to block emails though.
    • lucb1e 9y ago
      I suspect it has more to do with the American culture. Every time I watch something American, be it a TV show or YouTube from a big name, things are constantly bleeped out or you notice they don't mention swear words. It's super annoying - either accept it and stop beeping, or stop swearing all the fucking time. It's also not as if you have no idea what that beep meant.
      • mschuster91 9y ago
        > It's super annoying - either accept it and stop beeping IIRC the beeping at least of four-letter-words has to be done to avoid higher PG-ratings and/or fines from the FCC. Not much to do there.
• teekert 9y ago
  Why doesn't Intel just go to Linus and ask politely: "Ok, we f-ed up, here is a million dollars (or whatever, 10x his normal salary or something) can you please work with us tightly for some time? Thank you." I would really respect Intel if they would.
  • watwut 9y ago
    Why should they ask politely? It is not like the Linux mailing list would be polite environment. Nothing against impolite environment, people make case for it daily here and I don't care. But it combined with the standard expectation that when someone else talks to them he should be always polite is getting funny in that context.
    • sheepdestroyer 9y ago
      You'll get a pass at being impolite if you are technically in the right... Here Intel fucked up so they should be really really polite instead.
    • teekert 9y ago
      If you want something from someone you ask it politely. If you produce BS, you get told you produce BS. I'm guessing it's a cultural thing I'm also guessing you are an American. Americans coming here often tell us we are very direct and it takes getting used to. We often tell Americans we prefer they speak their mind and don't pretend something is great or we are best friends when it isn't the case. I'm from the Netherlands but I'm guessing Linus has his Finnish roots showing from time to time. Honestly, it's nice in the US to have waiters/waitresses that are nice, it feels insincere but I prefer it greatly to the sometimes outright moody waiters here. It's a culturing thing as well. If Intel would be sincere, they would just admin they produced BS (Linus is the best person to call BS on such patches) and apologize to Linus for wasting his time and ask how he would like to see the patches.
      • watwut 9y ago
        1.) I am not American. I am also not talking about Torwalds, because as far as I know Linus did not explicitly demanded to be spoken to "politely" (afaik). 2.) Talking politely and talking directly are orthogonal categories. You can be impolite while not direct and also polite while being direct. 3.) An environment in which people just speak their minds and is ok with people being impolite when those feel like it is characterized by everyone speaking is mind or being impolite, not just your hero. Meaning, you will not put emphasis on "be polite" when someone you dont like asks for something. 3.) I am pointing out the difference between how people who are not Torwalds demand that you talk to mailing list and what they defend as "good way to communicate" by people they admire. Because actual openly speaking culture is symmetric.
• chrisper 9y ago
  Whoever changed the title managed to make it less clear. With "Linus" in the title it was clear that it was Linux.
  • dang 9y ago
    I did that. We've observed over the years that celebrity names in titles tend to make for poorer discussion. HN is better when the focus is on content rather than personalities. https://hn.algolia.com/?sort=byDate&dateRange=all&type=comment&storyText=false&prefix=false&page=0&query=by:dang%20content%20personalities https://hn.algolia.com/?sort=byDate&dateRange=all&type=comme... Edit: ok, you guys have convinced me that this is a special case and we've put Linus back in the title above.
    • Valmar 9y ago
      Good to know. :)
    • askvictor 9y ago
      But it would certainly be good to have some context on the quote (i.e. that it has to do with Linux, Intel and Meltdown)
      • AHTERIX5000 9y ago
        Yeah, now the title is more clickbaity
    • jwilk 9y ago
      Then you should have posted the comment that you did. Also, cherry picking a quote and putting it in submission title is against HN guidelines.
    • dagurp 9y ago
      Too bad it didn't work
    • icelancer 9y ago
      That's a good blanket rule, but Linus' comments are uniquely important. He is a subject matter expert and context is important regarding who is doing the yelling. This isn't some celebrity who is famous for something irrelevant.
• bashcoder 9y ago
  The most striking thing here is that Linus has apparently dismissed incompetence as a rational explanation. Yes, he is often brash, but usually he is accusing someone of sheer stupidity. He does not do that here. Linus alleges that we are being lied to - that we don’t know the full story, nor Intel’s motives. Furthermore, we are left to wonder if Microsoft is also being fed “bullshit” patches, and if they may be less discerning than Linus regarding a proper solution.
  • icelancer 9y ago
    Linus calls people stupid when they are usually being stupid, at least in his eyes. He doesn't wantonly accuse people of stupidity for no reason. It's just that when he perceives stupid activity... well, he generally goes off. It's his main trigger.
  • StudentStuff 9y ago
    The root question is what else is Intel trying to cover up with these garbage patches? Are they afraid of power leakage across gates allowing an attacker to gain a higher level of privilege in certain generations of silicon, and trying to cover it up with these patches (hence some of the seemingly crazy things they do)?
    • bashcoder 9y ago
      Alternatively, it could also be in the interest of many for these patches to have an inordinate negative affect on performance with Intel CPUs. I am reminded that Linus has experience in the CPU industry (Transmeta), so he is in a position to see both sides on this.
      • majewsky 9y ago
        Sorta off-topic, but what did Linus actually do back at Transmeta? Did he contribute to their JIT compiler for x86?
        • gmueckl 9y ago
• Animats 9y ago
  Well, Torvalds has been heard from, along with Bloomberg and The Economist, as saying that Intel is in denial about this being a big, big problem.
  • walterbell 9y ago
    Has a major technology media outlet taken a similar position as Bloomberg and The Economist?
    • ryanlol 9y ago
      Are there any people who care about what the “technology media” says?
      • walterbell 9y ago
        Technology buyers? Technology sellers who pay tech media?
      • lucb1e 9y ago
        I do. I don't know Bloomberg or The Economist that well, but translating the media brands to Dutch ones, I'd definitely care more what Tweakers.net says about something than NOS - tech news versus general news. I know there are a few people at Tweakers who truly understand technology (like, they can probably write code) whereas at NOS you'd be happy if they explain the word "ransomware" correctly.
        • DangerousPie 9y ago
          The Economist is usually surprisingly well-informed about things like these. It's pretty much the only mainstream newspaper where I can read articles about my field without cringing.
          • fsloth 9y ago
            This. I'm not really sure if I need other news media in global affairs. If it's important Economist will cover it sooner or later, and if it's not, no one will remember it one month after the fact.
• gambiting 9y ago
  Am I the only person who finds this extremely difficult to read? The top says "David wrote" and then it looks like he's replying to a message from Linus Torvalds. So any quoted text is by Linus, right? But then....the letter is signed by Linus? So who wrote it? I know this is some ancient technology but Jesus, the user interface is horrendous.
  • dnt404-1 9y ago
    The first reading I had the same trouble, but you should watch the >> (Linus's previous post) and > (David's post) to figure out who said what. And this post is by Linus replying to David.
  • roel_v 9y ago
    Probably depends on how old you are. To me it was completely obvious and much, much clearer than most 'modern' user interfaces. Every person replying prefixes each line with > . Proper email clients do this automatically. This way you can tell from the number of >'s how far back on the 'stack' you have to go to know who wrote it. You start reading from the top, mentally associating an indent level (nr of >'s) with a person/email address. It's easy to follow any mail with up to say 3 or 4 different people; after that it takes some thinking sometimes, in long emails. I'm actually surprised at the number of people here complaining about the legibility. This is absolutely basic knowledge; or maybe I'm just even older than I imagine myself to be. How can someone who can't even figure this out write software? (I realize that not everybody on this site is a programmer nowadays, but still)
    • gambiting 9y ago
      I don't know, I'm 27 and a C++ programmer and found it difficult to figure out who's talking at the time. I'm just more used to more modern forums where each "block" is wrapped in quote tags with signature on top.
      • tatersolid 9y ago
        > I'm 27 and a C++ programmer Don’t tell Linus!
• delta1 9y ago
  > Have you _looked_ at the patches you are talking about? You should have - several of them bear your name. This made me so nervous on his behalf
  • johnflan 9y ago
    It is possible the patches are submitted on behalf of others.
    • deleted 9y ago
      [deleted]
• fouc 9y ago
  Are state actors or others trying to take advantage of meltdown needing fixes & patches to insert their own version of fixes & patches that end up benefiting them?
  • jnordwick 9y ago
    As far as we know, there has never been a single attack using either of specter or meltdown issues. No code had been found, nothing. It appears to be very difficult to take advantage of, and the initial idea of a JavaScript exploit seems to not be possible. Part of the reason for all of this might be that the attacker needs to run code on the target machine, and one the attacker can do that, there are far easier ways to read memory.
    • aidenn0 9y ago
      Meltdown is almost trivial to take advantage of, as these things go, and it was discovered independently by more than one researcher. That makes it somewhat more likely to have been exploited by a government level attacker. However, just being able to read all of kernelspace is more of a force-multiplier than being useful on its own. You still need to get your code executing in user-space to do anything, ant it's value even then is at least partly tied up in its ability to easily defeat KASLR.
      • jnordwick 9y ago
        Trivial, yet nobody has managed to produce a working exploit that doesn't require a running start. The poc exploits wouldn't work in the wild. They are running with interference of a real system. Also, meltdown requires the data to be snooped to be in L1D cache. So the current demo exploit has to keep pushing the data into cache to be read. Something simple like steal a password from sudo should be trivia right? I'd not convinced i need to worry. And making non public facing machines pay the price of the mitigation seems like too much.
        • ageofwant 9y ago
• krisives 9y ago
  It's upsetting that the media and some of the mainstream audience see Linus as a "crank" that only exists to complain and tear people down. Examples like this show how valuable his experience is. I would NEVER ask him to water himself down knowing it would likely make his technical analysis worse.
• beebmam 9y ago
  Really abusive language. There are ways to communicate his objections to the patches with extremely strong language WITHOUT resorting to abusive language. I wouldn't tolerate anyone treating me like this. There are unseen consequences to a wild tongue.
  • Kalium 9y ago
    Do you think Linus would get a maximally friendly reception if he said: > You clearly mean well. Your heart is in the right place. Thank you so much for all your hard work. There's this weird thing going on where it seems like a bunch of patches experiencing opportunity for improvement are being pushed. These patches also could maybe be better explained. > I don't understand. Can you help me understand, so we can fix our problems together? Again, thank you so much for your hard work! And, incidentally, does the above not just drip insincerity to you? It does to me, and I know how powerful the Dale Carnegie-esqe "complement sandwich" approach is. Linus is justifiably angry at someone screwing with code he is responsible for in ridiculous ways, without any real explanation of why a ridiculous approach was chosen. He's maybe a smidge less than fully satisfied with either point. The person in question really should know better on all points.
    • phyzome 9y ago
      You and I both know there's a (large) middle ground.
      • Kalium 9y ago
        Thank you for saying so and well spotted! You're absolutely right. There is very much a large middle ground. Is it possible that a middle ground of politely offering carefully tempered criticism might exist? It certainly does! Is it possible that it could potentially lack the same impact as the approach Linus used? This strikes me as also possible. My experience to date is that polite criticism carefully wrapped to avoid being upsetting in any way to someone emotionally invested in their work is often not received with the intended level of urgency. I'm sure that's just my total ignorance and lack of social graces. Can you please help me understand better?
• ageofwant 9y ago
  Linus is angry, that always makes me happy. Lord knows where we would be today if we had leaders like this more frequently through history.
  • eru 9y ago
    A leader getting angry is not a guarantee of getting good governance. For a very memorable performance, see https://www.youtube.com/watch?v=SyD4p8_y8Kw https://www.youtube.com/watch?v=SyD4p8_y8Kw
  • SmellyGeekBoy 9y ago
    It does make me worry about the day that Linus retires. I imagine the kernel has enough momentum to carry on for a while but without a leader like Linus I can see it very slowly starting to unravel and quality issues starting to sneak in, much like we're seeing with post-Jobs Apple. Thankfully it doesn't seem that time is coming any time soon.
    • txdv 9y ago
      Linus is a pure techie. No politics, no bullshitting around, your code sucks and he calls you out for it. The best kind of dictator to have.
    • kogepathic 9y ago
      > I can see it very slowly starting to unravel and quality issues starting to sneak in I know what you mean here, and I agree with you 100%. That being said, I can't help but chuckle because if you've ever looked at a vendor's GPL source code for the kernel (Android phone, NAS/router) you know it's the SoCs vendor's old SDK (lots of bodge) with the ODMs additional bodges for their product customizations. Yes, I am VERY glad that the mainline kernel has Linus and his nose for BS. But just go look at the vendor forks if you want to see some even worse shit than these patches! Allwinner's GPL is basically garbage. You can find quality rants from tkaiser (Armbian) about this. MediaTek doesn't even release theirs! Yes, this IS a GPL violation, and no they don't seem to care. At least Amlogic seems to have woken up and realized an active kernel development community is an asset for them.
• matt4077 9y ago
  I get that Linus is adored for "rejecting political correctness" or "speaking truth to power", but this email just shows how little such rants can achieve: he makes almost no argument, relying on his authority instead. i'm actually not quite sure what he's trying to achieve... There's no chance that a patch will make it into the kernel against his objections, so he doesn't really need to convince anybody. If he's trying to make a case against Intel, he's unlikely to succeed with the digital version of screaming expletives at people. I have absolutely no "moral" objections against the use of all the FUCKING BULLSHITS anybody wants. But there's a reason this style isn't used more often in politics/law/philosophy or any other profession trying to change peoples' minds: it really doesn't work. If anything, these rants show that Linus is unable to effectively use language to make his arguments. It makes him appear small, weak, and angry.
  • SmellyGeekBoy 9y ago
    Are we reading the same thing? He states very clearly the specific technical issues and behaviour from Intel that he perceives to be "FUCKING BULLSHIT".
  • icelancer 9y ago
    >> But there's a reason this style isn't used more often in politics/law/philosophy or any other profession trying to change peoples' minds: it really doesn't work. The United States has a president who literally just did that for an entire year.
• deleted 9y ago
  [deleted]
• fareesh 9y ago
  From what I understand of meltdown and spectre, they use a side channel attack to figure out CPU cache values after some speculative execution has been done. Can it not be solved by ensuring that the CPU either clears or purposefully does not cache memory that is read during speculative execution?
  • rocqua 9y ago
    I don't think its possible for a CPU to read memory without going through the cache. Moreover, the value of speculative execution drops really hard if you can't use any cache, as it means you are restricted to operating only on registers.
  • eecc 9y ago
    more or less... I'm surprised the CPU doesn't already flush caches after speculative execution branches are abandoned
    • plorkyeran 9y ago
      Flushing the cache after every branch misprediction would probably make branch prediction a net loss in performance.
      • eecc 9y ago
        Well not all caches, just the part tagged with the mispredicted branch
        • singingboyo 9y ago
          But that'd still be vulnerable. The issue isn't that you can read whatever was in/got brought into cache, the issue is that you can tell which part of the cache got evicted and infer values based on that.
• mrmondo 9y ago
  I wish people in this thread would stop turning the discussion into a straw-man argument about Linus’s language and focus their attention to the technical and security problems at hand. Some people are easily offended, some people easily offend, some people are direct, some people are indirect - get over it. What matters here is the quality of the code / workarounds that are being presented, by whom and what alternatives they are.
  • c3534l 9y ago
    > I wish people in this thread would stop turning the discussion into a straw-man argument about Linus’s language and focus their attention to the technical and security problems at hand. There wasn't much of a technical and security discussion in what was posted. Linus spent his time writing about his feelings and how hurt they were that someone did something he didn't like. Very little of substance or merit was communicated. If you consistently behave like a petulant child in a leadership role, expect people to gawk at it.
    • xelxebar 9y ago
      I feel like a lot of people judge Linus by some internal moral compass which just seems pointless to me. If anything is petulant and childish it's trying to control others for not fitting within some arbitrary set of personal rules. Linus does a good job at maintaining kernel development and often makes sharp technical commentary. By those measures his communication style seems to have been successful and practically helpful so far.
    • IntelMiner 9y ago
      As great as it is to sit in your chair and make snide remarks about him. The Linux Kernel seems to have a proven track record of success under that role That is to say, it is the largest collaborative software project in human history No amount of Linus being a "petulant child" can disprove the results of his style
    • kristjansson 9y ago
      That’s a pretty uncharitable analysis of the situation. The point of the attack are Intel’s future intentions as implied by the patches, and the degree which those intentions are at odds with Intel’s announced guidance. That seems like a very significant technical and security matter worth discussing, no matter the style of its delivery.
• yAnonymous 9y ago
  Could this whole disaster and the shitty patches have something to do with the remote kill switch (Anti Theft) Intel have in their CPUs? If someone could enable and trigger that remotely, it would make for fun times.
  • draugadrotten 9y ago
    It may interest you that a virus which kills its host won't spread as well as viruses which co-exist. This is basic from epidemics transmission rate. The longer an infected host keeps spreading the infection on, the more individuals will be infected. If the host is killed it will no longer spread the infection and therefore the infection may infect fewer hosts and this reduction in transmission rate alone may prevent a major outbreak. https://en.wikipedia.org/wiki/Mathematical_modelling_of_infectious_disease#The_SIR_model https://en.wikipedia.org/wiki/Mathematical_modelling_of_infe...
    • wongarsu 9y ago
      In nature, we usually only consider two success metrics: hosts infected and hosts killed. To maximize hosts infected, keeping the host alive and transmitting is very successful, so the most successful examples are those we barely even take note of (common cold, intestinal worms, etc.). To maximize hosts killed, in the physical world you either need a long incubation period where the host stays alive and transmitting (AIDS) or agressive transmission methods that humans have been getting quite good at shutting down (with the exception of transmission by mosquito). In the world of digital viruses traditional metrics can apply too (Ransomware is measured by hosts "killed", botnets by hosts infected), but those are no longer the only interesting metrics. A virus that spreads within a certain IP block and one month after inception bricks everything it can reach might be regarded as highly successful, despite killing itself in the process.
    • yAnonymous 9y ago
      Nothing you said is really related to the topic... classic computer viruses are a thing of the past and there are so many other attack vectors.
• kakarot 9y ago
  So somebody isn't telling the truth here. Somebody is pushing complete garbage for unclear reasons. Sorry for having to point that out. As it is, the patches are COMPLETE AND UTTER GARBAGE. They do literally insane things. They do things that do not make sense. That makes all your arguments questionable and suspicious. The patches do things that are not sane. Is Linus suggesting these patches are so bad that there could possibly be a camouflaged backdoor?
  • sgc 9y ago
    He certainly doesn't think it is a mistake. And that would fall within the spectrum of possibilities, but I would doubt anyone considers that as a probable reason, since it would be stupid to push something like that right now. Like future-destroying stupid.
    • kakarot 9y ago
      But if he doesn't think it's a mistake... what could it be?
      • sgc 9y ago
        He says: The whole IBRS_ALL feature to me very clearly says "Intel is not serious about this, we'll have a ugly hack that will be so expensive that we don't want to enable it by default, because that would look bad in benchmarks". So instead they try to push the garbage down to us. And they are doing it entirely wrong, even from a technical standpoint. I'm sure there is some lawyer there who says "we'll have to go through motions to protect against a lawsuit". But legal reasons do not make for good technology, or good patches that I should apply.
  • BonesJustice 9y ago
    Doubtful. Possibly a fix for an as-yet-undisclosed variant of the known attacks. Possibly mere ineptitude.
• deleted 9y ago
  [deleted]
• alvil 9y ago
  Dear Linus, now you can start your masturbation session, awaiting strong meltdown at the very end :) https://www.cio.com/article/2434264/open-source-tools/torvalds-calls-openbsd-group--masturbating-monkeys-.html https://www.cio.com/article/2434264/open-source-tools/torval...
• hmmmmmmmmmmm 9y ago
  The best bit of the thread is Linus getting corrected for mistakes in his rant. Not only was he excessively rude, he didn't even have the facts right. Embarrassing!
• daveheq 9y ago
  Sound like Intel is interested in allowing hacks, probably for government oversight.
  • jakebasile 9y ago
    This looks less like allowing hacks for states and more like covering their asses in benchmarks.
• PrimHelios 9y ago
  I always appreciate Linus' rants. In addition to being somewhat humorous, I usually learn a thing or two from them. It amazes me that people focus on how much of a jerk he's being instead of actually looking at the contents of his emails and learning something.
  • JoeAltmaier 9y ago
    Really? The internet is full of ranting commenters. They all have content of a sort. His don't deserve any more attention just because he's the subject of a hero-worship cult. Its actually possible to find thoughtful commentary on most any subject, without suffering jerks.
    • workthrowaway27 9y ago
      People only post his rants. Most of his replies are pretty benign.
      • JoeAltmaier 9y ago
        So with only a little counseling he could be a normal human being...
        • Valmar 9y ago
          He is a "normal" human being, lol. What a ridiculous comment.
    • justherefortart 9y ago
      Sometimes you just get sick of people pushing off garbage like it's a 3 star Michelin meal. As the primary kernel developer, the amount of crap he has to deal with gives him broad levity IMO. I've worked with engineers across many fields over my ~35 years of working. When they're ripping you a new one, you pretty much always deserve it. Putting shit on a plate is being a jerk, because you're not only wasting your time, you're wasting his time as well.
• nosequel 9y ago
  I want to create a new LKML account just to reply simply with > s/cool-aid/kool-aid/ Sometimes I just want to see the world burn.
  • ars 9y ago
    It was actually flavor-aid :) https://en.wikipedia.org/wiki/Drinking_the_Kool-Aid#Background https://en.wikipedia.org/wiki/Drinking_the_Kool-Aid#Backgrou...
• danjoc 9y ago
  >Not doing the right thing for meltdown would be completely unacceptable. Like not patching it at all. Like selling new ARM Chromebooks with no plans to ever patch meltdown in the firmware or kernel. Because that's what Google+Partners is doing with Rockchip Chromebooks AFAICT.
• frede 9y ago
  It seems the grandparent (authored by Linus, too) in the email thread is not available any more. Did Linus delete it?
• bertolo1988 9y ago
  Looks like Intel is trying to avoiding the best solution to not compromise benchmark scores.
• Aissen 9y ago
  Haha, two mails down, David Woodhouse doesn't disappoint and sends a message that'm copying here: http://lkml.iu.edu/hypermail/linux/kernel/1801.2/05282.html http://lkml.iu.edu/hypermail/linux/kernel/1801.2/05282.html I think we've covered the technical part of this now, not that you like it â not that any of us *like* it. But since the peanut gallery is paying lots of attention it's probably worth explaining it a little more for their benefit. This is all about Spectre variant 2, where the CPU can be tricked into mispredicting the target of an indirect branch. And I'm specifically looking at what we can do on *current* hardware, where we're limited to the hacks they can manage to add in the microcode. The new microcode from Intel and AMD adds three new features. One new feature (IBPB) is a complete barrier for branch prediction. After frobbing this, no branch targets learned earlier are going to be used. It's kind of expensive (order of magnitude ~4000 cycles). The second (STIBP) protects a hyperthread sibling from following branch predictions which were learned on another sibling. You *might* want this when running unrelated processes in userspace, for example. Or different VM guests running on HT siblings. The third feature (IBRS) is more complicated. It's designed to be set when you enter a more privileged execution mode (i.e. the kernel). It prevents branch targets learned in a less-privileged execution mode, BEFORE IT WAS MOST RECENTLY SET, from taking effect. But it's not just a 'set-and-forget' feature, it also has barrier-like semantics and needs to be set on *each* entry into the kernel (from userspace or a VM guest). It's *also* expensive. And a vile hack, but for a while it was the only option we had. Even with IBRS, the CPU cannot tell the difference between different userspace processes, and between different VM guests. So in addition to IBRS to protect the kernel, we need the full IBPB barrier on context switch and vmexit. And maybe STIBP while they're running. Then along came Paul with the cunning plan of "oh, indirect branches can be exploited? Screw it, let's not have any of *those* then", which is retpoline. And it's a *lot* faster than frobbing IBRS on every entry into the kernel. It's a massive performance win. So now we *mostly* don't need IBRS. We build with retpoline, use IBPB on context switches/vmexit (which is in the first part of this patch series before IBRS is added), and we're safe. We even refactored the patch series to put retpoline first. But wait, why did I say "mostly"? Well, not everyone has a retpoline compiler yet... but OK, screw them; they need to update. Then there's Skylake, and that generation of CPU cores. For complicated reasons they actually end up being vulnerable not just on indirect branches, but also on a 'ret' in some circumstances (such as 16+ CALLs in a deep chain). The IBRS solution, ugly though it is, did address that. Retpoline doesn't. There are patches being floated to detect and prevent deep stacks, and deal with some of the other special cases that bite on SKL, but those are icky too. And in fact IBRS performance isn't anywhere near as bad on this generation of CPUs as it is on earlier CPUs *anyway*, which makes it not quite so insane to *contemplate* using it as Intel proposed. That's why my initial idea, as implemented in this RFC patchset, was to stick with IBRS on Skylake, and use retpoline everywhere else. I'll give you "garbage patches", but they weren't being "just mindlessly sent around". If we're going to drop IBRS support and accept the caveats, then let's do it as a conscious decision having seen what it would look like, not just drop it quietly because poor Davey is too scared that Linus might shout at him again. :) I have seen *hand-wavy* analyses of the Skylake thing that mean I'm not actually lying awake at night fretting about it, but nothing concrete that really says it's OK. If you view retpoline as a performance optimisation, which is how it first arrived, then it's rather unconventional to say "well, it only opens a *little* bit of a security hole but it does go nice and fast so let's do it". But fine, I'm content with ditching the use of IBRS to protect the kernel, and I'm not even surprised. There's a *reason* we put it last in the series, as both the most contentious and most dispensable part. I'd be *happier* with a coherent analysis showing Skylake is still OK, but hey-ho, screw Skylake. The early part of the series adds the new feature bits and detects when it can turn KPTI off on non-Meltdown-vulnerable Intel CPUs, and also supports the IBPB barrier that we need to make retpoline complete. That much I think we definitely *do* want. There have been a bunch of us working on this behind the scenes; one of us will probably post that bit in the next day or so. I think we also want to expose IBRS to VM guests, even if we don't use it ourselves. Because Windows guests (and RHEL guests; yay!) do use it. If we can be done with the shouty part, I'd actually quite like to have a sensible discussion about when, if ever, we do IBPB on context switch (ptraceability and dumpable have both been suggested) and when, if ever, we set STIPB in userspace.
• shoover 9y ago
  Are people reading the rest of the thread? Linus admitted mistaking an acronym and changed his tone from "pushing garbage for unclear reasons" to just "garbage patches".
• ratinacage 9y ago
  > As a hack for existing CPUs, it's just about tolerable â as long as it > can die entirely by the next generation. > Certainly it's a nasty hack, but hey â the world was on fire and in the > end we didn't have to just turn the datacentres off and go back to goat > farming, so it's not all bad. Off-topic, but what is with the "â" in these sentences? Is that just some weird encoding error, or does it actually have meaning?
  • DerekL 9y ago
    Probably an encoding error. An m-dash is E2 80 94 in UTF-8. (An n-dash is E2 80 93.) I suspect that the original UTF-8 is misinterpreted as ISO 8859-1 or a similar encoding, where 0xE2 is “â”, and the other two are unassigned or control characters.
    • hinkley 9y ago
      Sounds about right. As a rule of thumb if you see a’s with accents you’re loooking at a UTF-8 encoding problem.
• kbenson 9y ago
  And here[1] is Woodhouse's coherent latest reply as of a couple hours ago on the issue, which explains for all us in the peanut gallery (his words, which I think are spot on) exactly what this is about, why it's included, how it actually affects the situation, why it was put forth at all, etc. It appears much less sinister than Linus was insinuating, but Linus has yet to reply. 1: http://lkml.iu.edu/hypermail/linux/kernel/1801.2/05282.html http://lkml.iu.edu/hypermail/linux/kernel/1801.2/05282.html
  • wilun 9y ago
    That's an interesting summary but I predict that Linus will destroy him for completely avoiding the hard question: why the fuck IBRS_ALL would not be on by default on future "fixed" chips, if on such CPU it would not be somehow crappy. And the risk of it becoming architectural (with that absurd default) is insane too.
    • dwmw2 9y ago
      Why would he do that? I completely agree with him on that, and I already told him I've been pushing back on it since I first heard about it a few weeks ago. Although there are technical reasons why we might need IBRS_ALL as a stop-gap before we can get to a proper solution, we bloody well ought to have line-of-sight to a proper solution in the same way that RDCL_NO says "it's OK, we fixed it" for Meltdown. But that's a separate topic. As I explicitly said, I limited that answer to the things we can do on current hardware.
• Waterluvian 9y ago
  I have a gut feeling that all of this madness is driven by legal and management terror. Doing the right thing likely means, to many people, admitting fault. Legal has likely banned anyone from doing anything that looks like an admission of guilt. Management and PR, etc. are all probably about saving face, too. The people who care about doing the right thing from a technology perspective likely don't have any power.
• faragon 9y ago
  Intel, please, hire Linus: If you can't beat him, join him.
• kelvin0 9y ago
  Yup, looks like it's time for me to pull out the good ole Amiga 500 from the closet, and use it as my main PC again. Guru meditation errors anyone?
• ksk 9y ago
  If someone were to call _you_ stupid, would you be more or less willing to help? How does calling other professionals stupid help the situation?
• jxramos 9y ago
  "Boy that escalated quickly..." https://youtu.be/ipsPgNEmAXI?t=301 https://youtu.be/ipsPgNEmAXI?t=301 Anchorman fight scene aftermath
• cromwellian 9y ago
  A lot of people trying to defend being a jerk as necessary in these circumstances. I think Google culture proves the opposite: Googley code and peer reviews, blameless postmortems, and a host of other mechanisms that de-escalate and de-personalize things. The Meltdown work at Google probably didn't begin with a rant about morons. It's possible to construct a culture where people can air grievances and criticize others without inducing flame wars. It only works for Linus because people won't go nuclear in the response, but for rank and file engineers, especially of equal stature, if you call someone a moron in a thread, it's likely to kill productivity and create a negative testosterone ladden atmosphere of people trying to avoid being wrong, and counter attacking others. I've worked at a lot of places where engineer got into heated shouting matches. It's is not a way to increase the probability of zeroing in on a problem, or reaching agreement faster.
  • jessaustin 9y ago
    Is this public discussion an attempt to "zero in" on this problem? Does anyone outside of Intel "agree" with their current approach? This is a more reasonable situation for the Torvalds method than many others in which he uses it.
    • quotheth 9y ago
      http://lkml.iu.edu/hypermail/linux/kernel/1801.2/05282.html http://lkml.iu.edu/hypermail/linux/kernel/1801.2/05282.html I would recommend reading this response. Here are some great excerpts: > That's why my initial idea, as implemented in this RFC patchset, was to stick with IBRS on Skylake, and use retpoline everywhere else. I'll give you "garbage patches", but they weren't being "just mindlessly sent around". If we're going to drop IBRS support and accept the caveats, then let's do it as a conscious decision having seen what it would look like, not just drop it quietly because poor Davey is too scared that Linus might shout at him again. :) > If we can be done with the shouty part, I'd actually quite like to have a sensible discussion about when, if ever, we do IBPB on context switch (ptraceability and dumpable have both been suggested) and when, if ever, we set STIPB in userspace. Those seem relevant to the thread. That said - it's really a good read for a technical overview of the issues and patches.
• calimac 9y ago
  you out there who play the absurdity of the situation down as anything short of conspiratorial and fraudulent and try to make the author out to be crazy are sheep. His tone is the result of witnessing you people, who are supposedly intelligent, act as ushers walking bystanders users into Stalin's Strawberry patch pits of current day, the ultimate surveillance state. Wake UP SHEEPLE
• beedogs 9y ago
  All the people here excoriating Torvalds for using mean language couldn't do in a lifetime what he does in the average week. Let the man get his job done and stop pretending to be offended by someone who communicates effectively. I'm tired of this pearl-clutching nonsense from the youngsters in tech.
• up2isomorphism 9y ago
  I am astonished by how many people here are complaining Linus being impolite while all what he is doing is to ensure we get a proper fix, not some garbage pushed by some large corporations. Garbage sometimes comes with a nice package, and mostly so nowadays.
• perpetualcrayon 9y ago
  This entire thread where folks are bashing Linus for his tone reminded me of this fun clip from the classic movie "Team America" (NSFW): https://www.youtube.com/watch?v=UIPSvIz9NDs https://www.youtube.com/watch?v=UIPSvIz9NDs
• bshanks 9y ago
  "the whole hardware interface is literally mis-designed by morons" Taken literally, this is not true.
• dschuetz 9y ago
  Yes, finally the engineering community is being divided into two large groups - one that actually focuses one the technical issue at hand and one that focuses on personal insults. Everybody is winning, I suspect?
• bungle 9y ago
  Someone brings shit to you front door in means that they'd like you to bring it in your house. What are you going to do? Most of us will react on such similarly to Linus.
• tripu 9y ago
  To me, Torvald's nasty attitude usually nullifies his (unquestionable) technical merits. There's no excuse to SHOUT, curse, and treat others as imbeciles on e-mail; even less so on fora as public and prominent as the linux kernel's mailing lists. As much as I decry patronising calls to make tech more "inclusive" and "nice", I must admit that people like Linus are a great argument in favour of that...
• watertom 9y ago
  The "rant" is an attention getter, no more no less, a bit of theater. Once everyone is paying attention, then the real purpose begins. Yes, there are other ways of doing it, but I would argue that none, are even remotely as effective gaining the necessary focused attention.
• ggm 9y ago
  A lot of comments feel like they are because Linus I want to observe this is somebody who used to work at Transmeta. They were not a large company, and whilst I don't think he directly did VLSI, he very probably understood the interaction of instruction set, chip level behaviour and upper system (specifically operating system and compiler) implications of what a chip does. I am interested in his response to Intel on that basis. I'd prefer he was less overtly rude and aggressive about it, but I think he manages to convey a real sense of anger and concern about things: How did Intel arrive at this fix. How did Intel discuss this fix with people who have to modify systems to work with it. Qui Bono.
• zrb05292 9y ago
  Having a sudden reason to push shadow software patches to nearly every device and server in the world...I wonder who would benefit from that...
• 5iveMinutes 9y ago
  I'm pushing great videos over at youtube! Come by and be part of it! https://youtu.be/HG-VClgOUCY https://youtu.be/HG-VClgOUCY Like, Comment and Subscribe for more great comps! 5ive Minutes Of Fame
• SpEd3Y 9y ago
  I have a question :) Can it be that Linus is so angry with people and their incompetence because he actually gives a shit about Linux and the code? I'm not interested if his rants are ethic or not, if they are effective or not. I'm just trying to understand why he's ranting? Because he's an ill adjusted person? Or is there something else? Linus is 'infamous' for being very angry with people who write shitty code. Why is that? If you read the chapters written by him in 'The Hacker Ethic', you find out that he codes because he's enjoying it, it's what makes him happy, so to speak. Therefore, he is invested in the code he writes. It's not just a job for him. It's his life's project, his 'baby' if you will. Can it be that because he's so emotionally invested into the code, when he sees that other people push shitty code and don't care about it, the intensity of the emotions he feels are way higher than the emotions of a manager who's just 'doing his job'? Can it be that because he cares so much, he's having a hard time not reacting so 'emotionally'?
• throwawaymanbot 9y ago
  Talking about Linus Torvalds personality when we should be really talking about Intel and one of the greatest computering cluster F*s of all time.. great thread hijack.