Re: [PATCH 1/2] KVM: SVM: Fix NMI path when NMI happens in guest mode

[Jan Kiszka <jan.kiszka@siemens.com>]

Am 13.01.2011 16:22, Joerg Roedel wrote:
> The vmexit path on SVM needs to restore the KERNEL_GS_BASE
> MSR in order to savely execute the NMI handler. Otherwise a
> pending NMI can occur after the STGI instruction and crash
> the machine.
> This makes it impossible to run perf and kvm in parallel on
> an AMD machine in a stable way.
> 
> Cc: stable@kernel.org
> Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
> ---
>  arch/x86/kvm/svm.c |    1 +
>  1 files changed, 1 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 25bd1bc..8b9bc72 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3637,6 +3637,7 @@ static void svm_vcpu_run(struct kvm_vcpu *vcpu)
>  
>  #ifdef CONFIG_X86_64
>  	wrmsrl(MSR_GS_BASE, svm->host.gs_base);
> +	wrmsrl(MSR_KERNEL_GS_BASE, current->thread.gs);
>  #else
>  	loadsegment(fs, svm->host.fs);
>  #endif

Doesn't this also obsolete the wrmsrl(MSR_KERNEL_GS_BASE) in svm_vcpu_put?

Jan

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