linux-kernel - Re: [PATCH] KVM: nVMX: Add VM-Enter failed tracepoints for super early checks

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Date:   Wed, 23 Sep 2020 18:03:11 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: nVMX: Add VM-Enter failed tracepoints for super
 early checks

On 12/08/20 20:06, Sean Christopherson wrote:
> Add tracepoints for the early consistency checks in nested_vmx_run().
> The "VMLAUNCH vs. VMRESUME" check in particular is useful to trace, as
> there is no architectural way to check VMCS.LAUNCH_STATE, and subtle
> bugs such as VMCLEAR on the wrong HPA can lead to confusing errors in
> the L1 VMM.
> 
> Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
> ---
>  arch/x86/kvm/vmx/nested.c | 10 +++++-----
>  1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/nested.c b/arch/x86/kvm/vmx/nested.c
> index 23b58c28a1c92..fb37f0972e78a 100644
> --- a/arch/x86/kvm/vmx/nested.c
> +++ b/arch/x86/kvm/vmx/nested.c
> @@ -3468,11 +3468,11 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>  	if (evmptrld_status == EVMPTRLD_ERROR) {
>  		kvm_queue_exception(vcpu, UD_VECTOR);
>  		return 1;
> -	} else if (evmptrld_status == EVMPTRLD_VMFAIL) {
> +	} else if (CC(evmptrld_status == EVMPTRLD_VMFAIL)) {
>  		return nested_vmx_failInvalid(vcpu);
>  	}
>  
> -	if (!vmx->nested.hv_evmcs && vmx->nested.current_vmptr == -1ull)
> +	if (CC(!vmx->nested.hv_evmcs && vmx->nested.current_vmptr == -1ull))
>  		return nested_vmx_failInvalid(vcpu);
>  
>  	vmcs12 = get_vmcs12(vcpu);
> @@ -3483,7 +3483,7 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>  	 * rather than RFLAGS.ZF, and no error number is stored to the
>  	 * VM-instruction error field.
>  	 */
> -	if (vmcs12->hdr.shadow_vmcs)
> +	if (CC(vmcs12->hdr.shadow_vmcs))
>  		return nested_vmx_failInvalid(vcpu);
>  
>  	if (vmx->nested.hv_evmcs) {
> @@ -3504,10 +3504,10 @@ static int nested_vmx_run(struct kvm_vcpu *vcpu, bool launch)
>  	 * for misconfigurations which will anyway be caught by the processor
>  	 * when using the merged vmcs02.
>  	 */
> -	if (interrupt_shadow & KVM_X86_SHADOW_INT_MOV_SS)
> +	if (CC(interrupt_shadow & KVM_X86_SHADOW_INT_MOV_SS))
>  		return nested_vmx_fail(vcpu, VMXERR_ENTRY_EVENTS_BLOCKED_BY_MOV_SS);
>  
> -	if (vmcs12->launch_state == launch)
> +	if (CC(vmcs12->launch_state == launch))
>  		return nested_vmx_fail(vcpu,
>  			launch ? VMXERR_VMLAUNCH_NONCLEAR_VMCS
>  			       : VMXERR_VMRESUME_NONLAUNCHED_VMCS);
> 

Queued, thanks.

Paolo