linux-kernel - Re: [PATCH v2 1/3] KVM: VMX: move msr_ia32_feature_control to vcpu

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Date:	Thu, 16 Jun 2016 19:57:14 +0800
From:	Haozhong Zhang <haozhong.zhang@...el.com>
To:	Borislav Petkov <bp@...e.de>
Cc:	kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
	rkrcmar@...hat.com, Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H . Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	linux-kernel@...r.kernel.org, Gleb Natapov <gleb@...nel.org>,
	Tony Luck <tony.luck@...el.com>,
	Andi Kleen <andi.kleen@...el.com>,
	Ashok Raj <ashok.raj@...el.com>
Subject: Re: [PATCH v2 1/3] KVM: VMX: move msr_ia32_feature_control to
 vcpu_vmx

On 06/16/16 13:49, Borislav Petkov wrote:
> On Thu, Jun 16, 2016 at 02:05:29PM +0800, Haozhong Zhang wrote:
> > msr_ia32_feature_control will be used for LMCE and not depend only on
> > nested anymore, so move it from struct nested_vmx to struct vcpu_vmx.
> > 
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@...el.com>
> > ---
> >  arch/x86/kvm/vmx.c | 11 ++++++-----
> >  1 file changed, 6 insertions(+), 5 deletions(-)
> > 
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index 57ec6a4..6b63f2d 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -421,7 +421,6 @@ struct nested_vmx {
> >  	struct pi_desc *pi_desc;
> >  	bool pi_pending;
> >  	u16 posted_intr_nv;
> > -	u64 msr_ia32_feature_control;
> >  
> >  	struct hrtimer preemption_timer;
> >  	bool preemption_timer_expired;
> > @@ -602,6 +601,8 @@ struct vcpu_vmx {
> >  	bool guest_pkru_valid;
> >  	u32 guest_pkru;
> >  	u32 host_pkru;
> > +
> > +	u64 msr_ia32_feature_control;
> >  };
> >  
> >  enum segment_cache_field {
> > @@ -2907,7 +2908,7 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> >  	case MSR_IA32_FEATURE_CONTROL:
> >  		if (!nested_vmx_allowed(vcpu))
> >  			return 1;
> > -		msr_info->data = to_vmx(vcpu)->nested.msr_ia32_feature_control;
> > +		msr_info->data = to_vmx(vcpu)->msr_ia32_feature_control;
> 
> Since this moves out of struct nested_vmx, that check above it:
> 
> 	if (!nested_vmx_allowed(vcpu))
> 
> should not influence it anymore, no?
> 
> Ditto for the rest.
> 

The same check in the set case still makes sense. I can remove the
check here and leave it in the set case.

Thanks,
Haozhong