linux-kernel - Re: [RFC PATCH v5 087/104] KVM: TDX: handle EXCEPTION_NMI and EXTERNAL

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Date:   Fri, 15 Apr 2022 16:49:03 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     isaku.yamahata@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...il.com, Jim Mattson <jmattson@...gle.com>,
        erdemaktas@...gle.com, Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v5 087/104] KVM: TDX: handle EXCEPTION_NMI and
 EXTERNAL_INTERRUPT

On 3/4/22 20:49, isaku.yamahata@...el.com wrote:
> From: Isaku Yamahata <isaku.yamahata@...el.com>
> 
> Because guest TD state is protected, exceptions in guest TDs can't be
> intercepted.  TDX VMM doesn't need to handle exceptions.
> tdx_handle_exit_irqoff() handles NMI and machine check.  Ignore NMI and
> machine check and continue guest TD execution.
> 
> For external interrupt, increment stats same to the VMX case.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> ---
>   arch/x86/kvm/vmx/tdx.c | 21 +++++++++++++++++++++
>   1 file changed, 21 insertions(+)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 2c35dcad077e..dc83414cb72a 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -800,6 +800,23 @@ void tdx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
>   						     tdexit_intr_info(vcpu));
>   }
>   
> +static int tdx_handle_exception(struct kvm_vcpu *vcpu)
> +{
> +	u32 intr_info = tdexit_intr_info(vcpu);
> +
> +	if (is_nmi(intr_info) || is_machine_check(intr_info))
> +		return 1;
> +
> +	kvm_pr_unimpl("unexpected exception 0x%x\n", intr_info);
> +	return -EFAULT;
> +}
> +
> +static int tdx_handle_external_interrupt(struct kvm_vcpu *vcpu)
> +{
> +	++vcpu->stat.irq_exits;
> +	return 1;
> +}
> +
>   static int tdx_handle_triple_fault(struct kvm_vcpu *vcpu)
>   {
>   	vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
> @@ -1131,6 +1148,10 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
>   	WARN_ON_ONCE(fastpath != EXIT_FASTPATH_NONE);
>   
>   	switch (exit_reason.basic) {
> +	case EXIT_REASON_EXCEPTION_NMI:
> +		return tdx_handle_exception(vcpu);
> +	case EXIT_REASON_EXTERNAL_INTERRUPT:
> +		return tdx_handle_external_interrupt(vcpu);
>   	case EXIT_REASON_EPT_VIOLATION:
>   		return tdx_handle_ept_violation(vcpu);
>   	case EXIT_REASON_EPT_MISCONFIG:

Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>