linux-kernel - Re: [PATCH v19 102/130] KVM: TDX: handle EXCEPTION_NMI and EXTERNAL

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Date: Mon, 1 Apr 2024 16:22:00 +0800
From: Chao Gao <chao.gao@...el.com>
To: <isaku.yamahata@...el.com>
CC: <kvm@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<isaku.yamahata@...il.com>, Paolo Bonzini <pbonzini@...hat.com>,
	<erdemaktas@...gle.com>, Sean Christopherson <seanjc@...gle.com>, Sagi Shahar
	<sagis@...gle.com>, Kai Huang <kai.huang@...el.com>, <chen.bo@...el.com>,
	<hang.yuan@...el.com>, <tina.zhang@...el.com>
Subject: Re: [PATCH v19 102/130] KVM: TDX: handle EXCEPTION_NMI and
 EXTERNAL_INTERRUPT

On Mon, Feb 26, 2024 at 12:26:44AM -0800, 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

tdx_handle_exit_irqoff() doesn't handle NMIs.

>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>
>Reviewed-by: Paolo Bonzini <pbonzini@...hat.com>
>---
> arch/x86/kvm/vmx/tdx.c | 23 +++++++++++++++++++++++
> 1 file changed, 23 insertions(+)
>
>diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
>index 0db80fa020d2..bdd74682b474 100644
>--- a/arch/x86/kvm/vmx/tdx.c
>+++ b/arch/x86/kvm/vmx/tdx.c
>@@ -918,6 +918,25 @@ void tdx_handle_exit_irqoff(struct kvm_vcpu *vcpu)
> 		vmx_handle_exception_irqoff(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;

Add a comment in code as well.

>+
>+	kvm_pr_unimpl("unexpected exception 0x%x(exit_reason 0x%llx qual 0x%lx)\n",
>+		intr_info,
>+		to_tdx(vcpu)->exit_reason.full, tdexit_exit_qual(vcpu));
>+	return -EFAULT;

-EFAULT looks incorrect.

>+}
>+
>+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;
>@@ -1390,6 +1409,10 @@ 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:
>-- 
>2.25.1
>
>