linux-kernel - Re: [PATCH 2/5] KVM: TDX: Exit with MEMORY_FAULT on unexpected pending S-EPT Violation

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Message-ID: <1d9d6e35ebf4658bbe48e6273eefff3267759519.camel@intel.com>
Date: Tue, 29 Jul 2025 22:27:34 +0000
From: "Edgecombe, Rick P" <rick.p.edgecombe@...el.com>
To: "maz@...nel.org" <maz@...nel.org>, "pbonzini@...hat.com"
	<pbonzini@...hat.com>, "seanjc@...gle.com" <seanjc@...gle.com>,
	"oliver.upton@...ux.dev" <oliver.upton@...ux.dev>
CC: "Annapurve, Vishal" <vannapurve@...gle.com>, "Li, Xiaoyao"
	<xiaoyao.li@...el.com>, "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
	"Hunter, Adrian" <adrian.hunter@...el.com>,
	"linux-arm-kernel@...ts.infradead.org"
	<linux-arm-kernel@...ts.infradead.org>, "kvm@...r.kernel.org"
	<kvm@...r.kernel.org>, "nik.borisov@...e.com" <nik.borisov@...e.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] KVM: TDX: Exit with MEMORY_FAULT on unexpected
 pending S-EPT Violation

On Tue, 2025-07-29 at 12:33 -0700, Sean Christopherson wrote:
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 3e0d4edee849..c2ef03f39c32 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1937,10 +1937,8 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
>  
>  	if (vt_is_tdx_private_gpa(vcpu->kvm, gpa)) {
>  		if (tdx_is_sept_violation_unexpected_pending(vcpu)) {
> -			pr_warn("Guest access before accepting 0x%llx on vCPU %d\n",
> -				gpa, vcpu->vcpu_id);
> -			kvm_vm_dead(vcpu->kvm);
> -			return -EIO;
> +			kvm_prepare_memory_fault_exit(vcpu, gpa, 0, true, false, true);
> +			return -EFAULT;
>  		}
>  		/*
>  		 * Always treat SEPT violations as write faults.  Ignore the

The vm_dead was added because mirror EPT will KVM_BUG_ON() if there is an
attempt to set the mirror EPT entry when it is already present. And the
unaccepted memory access will trigger an EPT violation for a mirror PTE that is
already set. I think this is a better solution irrespective of the vm_dead
changes.

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@...el.com>

But hmm, tangentially related, but Yan do we have a similar problem with
KVM_PRE_FAULT_MEMORY after we started setting pre_fault_allowed during TD
finalization?