linux-kernel - Re: [PATCH 0/2] x86, kvm: fix detection of KVM features when KVM and Hyper-V coexist

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Date:	Tue, 28 Jan 2014 20:19:01 -0200
From:	Marcelo Tosatti <mtosatti@...hat.com>
To:	Paolo Bonzini <pbonzini@...hat.com>
Cc:	linux-kernel@...r.kernel.org, gleb@...nel.org, hpa@...or.com,
	mingo@...hat.com, tglx@...utronix.de
Subject: Re: [PATCH 0/2] x86, kvm: fix detection of KVM features when KVM and
 Hyper-V coexist

On Mon, Jan 27, 2014 at 07:11:28PM +0100, Paolo Bonzini wrote:
> When KVM also presents Hyper-V features (which is useful because Windows
> behaves better), Linux guests prefer KVM because emulated leaves are at
> 0x40000000 and the native ones are at 0x40000100.
> 
> However, Linux is then not accounting for the offset when reading the
> available hypervisor features from CPUID.  Instead of looking at
> 0x40000101, it will always look at 0x40000001.
> 
> This series makes sure that features such as async page faults or steal
> time are available even if, for whatever reason, Hyper-V features are
> enabled.
> 
> As a side effect, patch 1 makes a bunch of code non inline, which also
> makes sense since it should only be called during initialization.  As 
> a result, vmlinux .text size decreases by 96 bytes.
> 
> Please review!
> 
> Paolo Bonzini (2):
>   x86, kvm: cache the base of the KVM cpuid leaves
>   x86, kvm: correctly access the KVM_CPUID_FEATURES leaf at 0x40000101
> 
>  arch/x86/include/asm/kvm_para.h | 33 ++++++++++++---------------------
>  arch/x86/kernel/kvm.c           | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 43 insertions(+), 21 deletions(-)
> 
> -- 
> 1.8.3.1

Reviewed-by: Marcelo Tosatti <mtosatti@...hat.com>

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