Re: [PATCH] KVM: x86: remove vcpu's CPL check in host invoked vcpu's xcr set process

[Paolo Bonzini <pbonzini@redhat.com>]

Il 14/06/2013 09:36, Zhanghaoyu (A) ha scritto:
> __kvm_set_xcr function does the CPL check when set xcr. __kvm_set_xcr is called in two flows,
> one is invoked by guest, call stack shown as below,
> handle_xsetbv(or xsetbv_interception)
>   kvm_set_xcr
>     __kvm_set_xcr
> the other one is invoked by host(QEMU), call stack shown as below,
> kvm_arch_vcpu_ioctl
>   kvm_vcpu_ioctl_x86_set_xcrs
>     __kvm_set_xcr
> 
> The former does need the CPL check, but the latter does not.
> 
> Signed-off-by: Zhang Haoyu <haoyu.zhang@huawei.com>
> ---
>  arch/x86/kvm/x86.c                            |    5 +-
>  1 file changed, 2 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 094b5d9..16ff44e 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -582,8 +582,6 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
>  		 if (index != XCR_XFEATURE_ENABLED_MASK)
>  		 		 return 1;
>  		 xcr0 = xcr;
> -		 if (kvm_x86_ops->get_cpl(vcpu) != 0)
> -		 		 return 1;
>  		 if (!(xcr0 & XSTATE_FP))
>  		 		 return 1;
>  		 if ((xcr0 & XSTATE_YMM) && !(xcr0 & XSTATE_SSE))
> @@ -597,7 +595,8 @@ int __kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
>  
>  int kvm_set_xcr(struct kvm_vcpu *vcpu, u32 index, u64 xcr)
>  {
> -		 if (__kvm_set_xcr(vcpu, index, xcr)) {
> +		 if ((kvm_x86_ops->get_cpl(vcpu) != 0) ||
> +		      __kvm_set_xcr(vcpu, index, xcr)) {
>  		 		 kvm_inject_gp(vcpu, 0);
>  		 		 return 1;
>  		 }
> 1.7.3.1.msysgit.0
> 

Applied to master, but check your setup because I had to do so manually.
 Your patch has 2 tabs + 1 space for each indentation level (??), the
file only has one tab.

This time the patch was pretty simple and may even be worth having in
3.9, but next time I'd ask you to resubmit.

Can you write a testcase for kvm-unit-tests?

Paolo