Re: [PATCH 01/10] KVM: VMX: Use vpid_sync_context() directly when possible

[Sean Christopherson <sean.j.christopherson@intel.com>]

On Fri, Feb 21, 2020 at 02:17:46PM +0100, Vitaly Kuznetsov wrote:
> Sean Christopherson <sean.j.christopherson@intel.com> writes:
> 
> > Use vpid_sync_context() directly for flows that run if and only if
> > enable_vpid=1, or more specifically, nested VMX flows that are gated by
> > vmx->nested.msrs.secondary_ctls_high.SECONDARY_EXEC_ENABLE_VPID being
> > set, which is allowed if and only if enable_vpid=1.  Because these flows
> > call __vmx_flush_tlb() with @invalidate_gpa=false, the if-statement that
> > decides between INVEPT and INVVPID will always go down the INVVPID path,
> > i.e. call vpid_sync_context() because
> > "enable_ept && (invalidate_gpa || !enable_vpid)" always evaluates false.
> >
> > This helps pave the way toward removing @invalidate_gpa and @vpid from
> > __vmx_flush_tlb() and its callers.
> >
> > No functional change intended.
> >
> > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
> > ---
> >  arch/x86/kvm/vmx/nested.c | 8 ++++----
> >  1 file changed, 4 insertions(+), 4 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> > index 657c2eda357c..19ac4083667f 100644
> > --- a/arch/x86/kvm/vmx/nested.c
> > +++ b/arch/x86/kvm/vmx/nested.c
> > @@ -2466,7 +2466,7 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
> >  		if (nested_cpu_has_vpid(vmcs12) && nested_has_guest_tlb_tag(vcpu)) {
> >  			if (vmcs12->virtual_processor_id != vmx->nested.last_vpid) {
> >  				vmx->nested.last_vpid = vmcs12->virtual_processor_id;
> > -				__vmx_flush_tlb(vcpu, nested_get_vpid02(vcpu), false);
> > +				vpid_sync_context(nested_get_vpid02(vcpu));
> >  			}
> >  		} else {
> >  			/*
> > @@ -5154,17 +5154,17 @@ static int handle_invvpid(struct kvm_vcpu *vcpu)
> >  			__invvpid(VMX_VPID_EXTENT_INDIVIDUAL_ADDR,
> >  				vpid02, operand.gla);
> >  		} else
> > -			__vmx_flush_tlb(vcpu, vpid02, false);
> > +			vpid_sync_context(vpid02);
> 
> This is a pre-existing condition but coding style requires braces even
> for single statements when they were used in another branch.

I'll fix this in v2.

> >  		break;
> >  	case VMX_VPID_EXTENT_SINGLE_CONTEXT:
> >  	case VMX_VPID_EXTENT_SINGLE_NON_GLOBAL:
> >  		if (!operand.vpid)
> >  			return nested_vmx_failValid(vcpu,
> >  				VMXERR_INVALID_OPERAND_TO_INVEPT_INVVPID);
> > -		__vmx_flush_tlb(vcpu, vpid02, false);
> > +		vpid_sync_context(vpid02);
> >  		break;
> >  	case VMX_VPID_EXTENT_ALL_CONTEXT:
> > -		__vmx_flush_tlb(vcpu, vpid02, false);
> > +		vpid_sync_context(vpid02);
> >  		break;
> >  	default:
> >  		WARN_ON_ONCE(1);
> 
> Seems to be no change indeed,

Heh, that's about the same level of confidence I had :-)
 
> Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> 
> -- 
> Vitaly
>