4 ms·

Why not go all they way and let everything run in ring 0? Then Intel can prefetch beyond kernel entry calls again! And we also can see how AMD will performing u

Why not go all they way and let everything run in ring 0? Then Intel can prefetch beyond kernel entry calls again! And we also can see how AMD will performing under the same conditions! With Intels wave of TSX disabling patches going over all the previous CPU generations, AMD apparently got it right by never bringing their own version into production at all.

Bancakes 5y ago
Cool, like 6th/7th gen consoles used to be. Simple, single-app OSs.
DaiPlusPlus 5y ago
> Why not go all they way and let everything run in ring 0? How would you get memory protection or debugger support then? Or the very-likely use-case of rendering live (i.e. untrusted) web-content in-game? That would require a modern engine like Chromium which in-turn necessitates per-process isolation. Also, no-one wants to have to reboot their entire computer system just because some application code crashed. Even if preemptive scheduling and the MMU works in ring 0 all processes in ring 0 can manipulate the MMU registers, so a misbehaving process can still bring down the entire system. Bad idea. Even dedicated HPC applications need it - remember that the HPC/scientific-computing/batch-job-processing model is the whole reason that operating-systems exist today: they're highly evolved successors to job-control programs (e.g. Chippewa Operating System). So I don't think they'd want to give up all the improvements of the past 50+ years. Ultimately we're just arguing about the principle of how the user who owns the computer should be in ultimate control over the hardware - but unfortunately Apple has demonstrated that principle is unnecessary to make obscene profits and also runs contrary to the realities of running a large secure platform today. We shall see how this ends-up...
- saagarjha 5y ago
  (I understood the parent comment to be sarcasm.)
alerighi 5y ago
In theory, wouldn't make sense to run all the code that runs as the root user as ring zero? The root user still can access read/write the whole memory of the system anyway via /dev/mem, load kernel modules, and do practically anything on the system. In that context, a change of privilege is useless in practice, and can lead to performance degradation. This will lead performance benefits in most system daemons, notably programs that interact closely with the kernel like systemd.
- saagarjha 5y ago
  Code that crashes in ring zero takes down the system. Do you really want your computer to die if systemd segfaults?

Bancakes 5y ago

Cool, like 6th/7th gen consoles used to be. Simple, single-app OSs.

DaiPlusPlus 5y ago

> Why not go all they way and let everything run in ring 0? How would you get memory protection or debugger support then? Or the very-likely use-case of rendering live (i.e. untrusted) web-content in-game? That would require a modern engine like Chromium which in-turn necessitates per-process isolation. Also, no-one wants to have to reboot their entire computer system just because some application code crashed. Even if preemptive scheduling and the MMU works in ring 0 all processes in ring 0 can manipulate the MMU registers, so a misbehaving process can still bring down the entire system. Bad idea. Even dedicated HPC applications need it - remember that the HPC/scientific-computing/batch-job-processing model is the whole reason that operating-systems exist today: they're highly evolved successors to job-control programs (e.g. Chippewa Operating System). So I don't think they'd want to give up all the improvements of the past 50+ years. Ultimately we're just arguing about the principle of how the user who owns the computer should be in ultimate control over the hardware - but unfortunately Apple has demonstrated that principle is unnecessary to make obscene profits and also runs contrary to the realities of running a large secure platform today. We shall see how this ends-up...

saagarjha 5y ago
(I understood the parent comment to be sarcasm.)

alerighi 5y ago

In theory, wouldn't make sense to run all the code that runs as the root user as ring zero? The root user still can access read/write the whole memory of the system anyway via /dev/mem, load kernel modules, and do practically anything on the system. In that context, a change of privilege is useless in practice, and can lead to performance degradation. This will lead performance benefits in most system daemons, notably programs that interact closely with the kernel like systemd.

saagarjha 5y ago
Code that crashes in ring zero takes down the system. Do you really want your computer to die if systemd segfaults?