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

From: Andy Lutomirski
Date: Wed Oct 28 2015 - 01:23:11 EST

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.

BTW, Frederic, I have a static key patch coming that I think you'll
like. I'll send it tomorrow once I'm in front of a real computer.

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