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

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Date: Wed, 3 Apr 2024 11:51:03 -0700
From: Isaku Yamahata <isaku.yamahata@...el.com>
To: Chao Gao <chao.gao@...el.com>
Cc: isaku.yamahata@...el.com, 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,
	isaku.yamahata@...ux.intel.com
Subject: Re: [PATCH v19 102/130] KVM: TDX: handle EXCEPTION_NMI and
 EXTERNAL_INTERRUPT

On Mon, Apr 01, 2024 at 04:22:00PM +0800,
Chao Gao <chao.gao@...el.com> wrote:

> 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.

Will it to tdx_handle_exception().


> >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.

Sure.


> >+
> >+	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.

As this is unexpected exception, we should exit to to the user-space with
KVM_EXIT_EXCEPTION. Then QEMU will abort with message.
-- 
Isaku Yamahata <isaku.yamahata@...el.com>