Re: [PATCH 2/3] context_tracking: avoid irq_save/irq_restore on guest entry and exit

From: Andy Lutomirski
Date: Wed Oct 28 2015 - 01:21:23 EST

On Tue, Oct 27, 2015 at 6:39 PM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
> guest_enter and guest_exit must be called with interrupts disabled,
> since they take the vtime_seqlock with write_seq{lock,unlock}.
> 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.
> Split the body of context_tracking_entry and context_tracking_exit
> out to __-prefixed functions, and use them from KVM.
> Rik van Riel has measured this to speed up a tight vmentry/vmexit
> loop by about 2%.

Looks generally sensible. I'm not familiar enough with the code to
call it reviewed-by while sitting on the airport shuttle.

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