On 06/03/16 17:34, Radim Krčmář wrote:
> 2016-06-03 14:08+0800, Haozhong Zhang:
> > On Intel platforms, this patch adds LMCE to KVM MCE supported
> > capabilities and handles guest access to LMCE related MSRs.
> >
> > Signed-off-by: Ashok Raj <ashok.raj@xxxxxxxxx>
> > Signed-off-by: Haozhong Zhang <haozhong.zhang@xxxxxxxxx>
> > ---
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > @@ -2863,6 +2863,11 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
> > return 0;
> > }
> >
> > +static inline bool vmx_feature_control_msr_required(struct kvm_vcpu *vcpu)
>
> I'd call it "present", rather than "required". SDM does so for other
> MSRs and it is easier to understand in the condition that returns #GP if
> this function is false.
>
Agree, I'll change.
> > +{
> > + return nested_vmx_allowed(vcpu) || (vcpu->arch.mcg_cap & MCG_LMCE_P);
> > +}
> > @@ -2904,8 +2909,15 @@ static int vmx_get_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > case MSR_IA32_FEATURE_CONTROL:
> > - if (!nested_vmx_allowed(vcpu))
> > + if (!vmx_feature_control_msr_required(vcpu))
> > return 1;
> > msr_info->data = to_vmx(vcpu)->nested.msr_ia32_feature_control;
>
> (MSR_IA32_FEATURE_CONTROL does not depend only on nested anymore, so
> moving msr_ia32_feature_control from struct nested_vmx to struct
> vcpu_vmx would make sense.)
>
will move in the next version
> > break;
> > @@ -2997,8 +3009,17 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> > + case MSR_IA32_MCG_EXT_CTL:
> > + if (!(vcpu->arch.mcg_cap & MCG_LMCE_P) ||
> > + !(to_vmx(vcpu)->nested.msr_ia32_feature_control &
> > + FEATURE_CONTROL_LMCE))
>
> (This check is used twice and could be given a name too,
> "vmx_mcg_ext_ctl_msr_present()"?)
>
will change
> > + return 1;
> > + if (data && data != 0x1)
>
> (data & ~MCG_EXT_CTL_LMCE_EN)
>
> is a clearer check for reserved bits.
>
ditto
> > + return -1;
> > + vcpu->arch.mcg_ext_ctl = data;
> > + break;
> > case MSR_IA32_FEATURE_CONTROL:
> > - if (!nested_vmx_allowed(vcpu) ||
> > + if (!vmx_feature_control_msr_required(vcpu) ||
> > (to_vmx(vcpu)->nested.msr_ia32_feature_control &
> > FEATURE_CONTROL_LOCKED && !msr_info->host_initiated))
> > return 1;
>
> Does hardware throw #GP when FEATURE_CONTROL_LMCE is set without
> MCG_LMCE_P?
>
Yes, SDM vol 2 says setting reserved bits of MSR causes #GP.
> (We could emulate that by having a mask of valid bits and also use that
> mask in place of vmx_feature_control_msr_required(). I don't think
> there is a reason to have only vmx_feature_control_msr_required() if
> the hardware can #GP on individual bits too.)
>
Oh yes, I should also validate the individual bits. I'll add it in the
next version.
Thanks,
Haozhong
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