linux-kernel - RE: [PATCH v1 13/23] KVM: VMX: Handle VMX nested exception for FRED

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Message-ID: <SA1PR11MB67348D3637C2BC6B107C5CCAA8B1A@SA1PR11MB6734.namprd11.prod.outlook.com>
Date:   Wed, 15 Nov 2023 03:03:01 +0000
From:   "Li, Xin3" <xin3.li@...el.com>
To:     "Gao, Chao" <chao.gao@...el.com>
CC:     "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
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        "Shankar, Ravi V" <ravi.v.shankar@...el.com>
Subject: RE: [PATCH v1 13/23] KVM: VMX: Handle VMX nested exception for FRED

> >+		if (idt_vectoring_info & VECTORING_INFO_DELIVER_CODE_MASK)
> >+			kvm_requeue_exception_e(vcpu, vector,
> vmcs_read32(error_code_field),
> >+						idt_vectoring_info &
> INTR_INFO_NESTED_EXCEPTION_MASK);
> >+		else
> >+			kvm_requeue_exception(vcpu, vector,
> >+					      idt_vectoring_info &
> INTR_INFO_NESTED_EXCEPTION_MASK);
> 
> Exiting-event identification can also have bit 13 set, indicating a nested
> exception encountered and caused VM-exit. when reinjecting the exception to
> guests, kvm needs to set the "nested" bit, right? I suspect some changes
> to e.g., handle_exception_nmi() are needed.

The current patch relies on kvm_multiple_exception() to do that.  But TBH,
I'm not sure it can recognize all nested cases.  I probably should revisit
it.