linux-kernel - Re: [PATCH 0/3] kvm: APICv register write workaround

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Date:	Fri, 31 Oct 2014 16:06:49 +0100
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Radim Krčmář <rkrcmar@...hat.com>,
	linux-kernel@...r.kernel.org
CC:	kvm@...r.kernel.org, Gleb Natapov <gleb@...nel.org>,
	Marcelo Tosatti <mtosatti@...hat.com>
Subject: Re: [PATCH 0/3] kvm: APICv register write workaround



On 30/10/2014 15:06, Radim Krčmář wrote:
> APICv traps register writes, so we can't retrieve previous value, but
> our code depends on detecting changes.

Applied, thanks.

Paolo

> Apart from disabling APIC register virtualization, we can detect the
> change by using extra memory.  One value history is enough, but we still
> don't want to keep it for every APIC register, for performance reasons.
> This leaves us with either a new framework, or exceptions ...
> The latter options fits KVM's path better [1,2].
> 
> And when we already mirror a part of registers, optimizing access is
> acceptable [3].  (Squashed to keep bisecters happy.)
> 
> ---
> Radim Krčmář (3):
>   KVM: x86: detect SPIV changes under APICv
>   KVM: x86: detect LVTT changes under APICv
>   KVM: x86: optimize some accesses to LVTT and SPIV
> 
>  arch/x86/kvm/lapic.c | 32 +++++++++++++++++---------------
>  arch/x86/kvm/lapic.h |  8 +++++---
>  2 files changed, 22 insertions(+), 18 deletions(-)
> 
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