Re: [PATCH 3/3] x86: context_tracking: avoid irq_save/irq_restore on kernel entry and exit

From: Andy Lutomirski
Date: Mon Mar 14 2016 - 15:23:42 EST

On Tue, Oct 27, 2015 at 10:22 PM, Andy Lutomirski <luto@xxxxxxxxxxxxxx> wrote:
> On Tue, Oct 27, 2015 at 6:39 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>> x86 always calls user_enter and user_exit with interrupt disabled.
>> Therefore, it is not necessary to check for exceptions, nor to
>> save/restore the IRQ state, when context tracking functions are
>> called by guest_enter and guest_exit.
>> Use the previously introduced __context_tracking_entry and
>> __context_tracking_exit.
> x86 isn't ready for this yet. We could do a quick-and-dirty fix with
> explicit IRQs-on-and-off much protected by the static key, or we could
> just wait until I finish the syscall cleanup. I favor the latter, but
> you're all welcome to do the former and I'll review it.

Once Linus pulls tip:x86/asm, x86 should be ready for this. Want to try again?