3 ms·

Are specter and friends finally fixed in Zen4?

neogodless 4y ago
Have not found anything definitive, but I think it was fixed starting with Zen 3. https://wccftech.com/amd-and-intel-cpus-remain-vulnerable-to-spectre-v2-vulnerabilities-even-after-patches/ https://wccftech.com/amd-and-intel-cpus-remain-vulnerable-to... https://www.amd.com/en/corporate/product-security https://www.amd.com/en/corporate/product-security https://meltdownattack.com/ https://meltdownattack.com/ Likely need to dig into PDFs to get answers.
- sylware 4y ago
  How hard would have it be to state clearly "all known specter/meltdown/similar exploits" were fixed from Zen3. I guess it was stated somewhere, and I missed it.
Symmetry 4y ago
Spectre is essentially intrinsic to any out of order CPU that uses caches and needs to be addressed at the software level if you have information that shouldn't be leaking within a software process. Meltdown never affected AMD CPUs in the first place.
chaimanmeow 4y ago
Given that the number of transistors per square mm is now so ridiculously mind boggling, and how many cores you can easily fit onto a 100mm2 budget die (on 5 or 6nm, more so on 3nm) AMD really needs to get with the times and rethink SMT, and replace it with a more general multithreading that is in tune with the big.little additions to x86 and acorn risc software ecosystem. Little cores (real or logical), with small to no reorder buffer, can be nicely asked to forgo any speculative execution. Browsers worth their salt will take advantage of the fact that high risk threads (such as javascript, wasm, and other interpreted/jit code) can be asked by default to run on little cores. That is, unless a user left clicks on a tab to manually override the default, any scripts arising from said tab is taskset to small cores only. Browsers might also have a whitelist option regarding scripts originating from whitelisted internet domain and their ability to run on big cores. Likewise the OS should allow the user to easily taskset any application to their desired set of cores (unix already does, via taskset command). So instead of SMT2, I'd really like Zen 5 to have MT4, or MT5, where those multithreading schemes have just one big thread (massive reorder buffer) and three to four little threads (no ROB or tiny ROB) with an option to disable speculative execution---the latter keeping all those idle pipelines a little less idle.

Have not found anything definitive, but I think it was fixed starting with Zen 3. https://wccftech.com/amd-and-intel-cpus-remain-vulnerable-to-spectre-v2-vulnerabilities-even-after-patches/ https://wccftech.com/amd-and-intel-cpus-remain-vulnerable-to... https://www.amd.com/en/corporate/product-security https://www.amd.com/en/corporate/product-security https://meltdownattack.com/ https://meltdownattack.com/ Likely need to dig into PDFs to get answers.

sylware 4y ago
How hard would have it be to state clearly "all known specter/meltdown/similar exploits" were fixed from Zen3. I guess it was stated somewhere, and I missed it.

Symmetry 4y ago

Spectre is essentially intrinsic to any out of order CPU that uses caches and needs to be addressed at the software level if you have information that shouldn't be leaking within a software process. Meltdown never affected AMD CPUs in the first place.

chaimanmeow 4y ago

Given that the number of transistors per square mm is now so ridiculously mind boggling, and how many cores you can easily fit onto a 100mm2 budget die (on 5 or 6nm, more so on 3nm) AMD really needs to get with the times and rethink SMT, and replace it with a more general multithreading that is in tune with the big.little additions to x86 and acorn risc software ecosystem. Little cores (real or logical), with small to no reorder buffer, can be nicely asked to forgo any speculative execution. Browsers worth their salt will take advantage of the fact that high risk threads (such as javascript, wasm, and other interpreted/jit code) can be asked by default to run on little cores. That is, unless a user left clicks on a tab to manually override the default, any scripts arising from said tab is taskset to small cores only. Browsers might also have a whitelist option regarding scripts originating from whitelisted internet domain and their ability to run on big cores. Likewise the OS should allow the user to easily taskset any application to their desired set of cores (unix already does, via taskset command). So instead of SMT2, I'd really like Zen 5 to have MT4, or MT5, where those multithreading schemes have just one big thread (massive reorder buffer) and three to four little threads (no ROB or tiny ROB) with an option to disable speculative execution---the latter keeping all those idle pipelines a little less idle.