Re: [PATCH v7 1/3] KVM: x86: add support for user wait instructions

[Tao Xu]

On 7/12/2019 11:13 PM, Sean Christopherson wrote:
> On Fri, Jul 12, 2019 at 04:29:05PM +0800, Tao Xu wrote:
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index 46af3a5e9209..a4d5da34b306 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -2048,6 +2048,7 @@ static void prepare_vmcs02_early(struct vcpu_vmx *vmx, struct vmcs12 *vmcs12)
> >   				  SECONDARY_EXEC_ENABLE_INVPCID |
> >   				  SECONDARY_EXEC_RDTSCP |
> >   				  SECONDARY_EXEC_XSAVES |
> > +				  SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
> >   				  SECONDARY_EXEC_VIRTUAL_INTR_DELIVERY |
> >   				  SECONDARY_EXEC_APIC_REGISTER_VIRT |
> >   				  SECONDARY_EXEC_ENABLE_VMFUNC);
> > diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
> > index d98eac371c0a..f411c9ae5589 100644
> > --- a/arch/x86/kvm/vmx/vmx.c
> > +++ b/arch/x86/kvm/vmx/vmx.c
> > @@ -2247,6 +2247,7 @@ static __init int setup_vmcs_config(struct vmcs_config *vmcs_conf,
> >   			SECONDARY_EXEC_RDRAND_EXITING |
> >   			SECONDARY_EXEC_ENABLE_PML |
> >   			SECONDARY_EXEC_TSC_SCALING |
> > +			SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE |
> >   			SECONDARY_EXEC_PT_USE_GPA |
> >   			SECONDARY_EXEC_PT_CONCEAL_VMX |
> >   			SECONDARY_EXEC_ENABLE_VMFUNC |
> > @@ -3984,6 +3985,25 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx)
> >   		}
> >   	}
> >   
> > +	if (vmcs_config.cpu_based_2nd_exec_ctrl &
> > +		SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE) {
>
> This should be aligned with the beginning of the conditional.
> Alternatively, add a vmx_waitpkg_supported() helper, which is fairly
> ubiquitous even when there is only a single call site.

OK, Thank you for your suggestion.
> > +		/* Exposing WAITPKG only when WAITPKG is exposed */
> No need for this comment.  It's also oddly worded, e.g. the second
> "exposed" should probably be "enabled"?
>
> > +		bool waitpkg_enabled =
> > +			guest_cpuid_has(vcpu, X86_FEATURE_WAITPKG);
> > +
> > +		if (!waitpkg_enabled)
> > +			exec_control &= ~SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
> > +
> > +		if (nested) {
> > +			if (waitpkg_enabled)
> > +				vmx->nested.msrs.secondary_ctls_high |=
> > +					SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
> > +			else
> > +				vmx->nested.msrs.secondary_ctls_high &=
> > +					~SECONDARY_EXEC_ENABLE_USR_WAIT_PAUSE;
> > +		}
> > +	}
> > +
> >   	vmx->secondary_exec_control = exec_control;
> >   }
> >   
> > --
> > 2.20.1