Re: [PATCH] KVM: TDX: Synthesize SHUTDOWN instead of returning -EIO on unhandled EPT violation

[Xiaoyao Li]

On 9/24/2026 12:33 AM, Sean Christopherson wrote:
> Synthesize a triple fault, i.e. exit to userspace with KVM_EXIT_SHUTDOWN,
> instead of returning -EIO from KVM_RUN if KVM encounters an EPT Violation
> due to a guest access to a pending page.  Returning -EIO implies KVM is
> buggy, and most VMMs will respond by completely terminating the VM, versus
> rebooting the VM in response to KVM_EXIT_SHUTDOWN.  I.e. give the VMM the
> option of trying to keep the VM (from the end user's perspective) alive.

But reboot isn't good, neither.

I still think a new specific exit reason[1] would be better, as I suggested before.

[1] https://lore.kernel.org/kvm/1b0ea352-c645-461b-9e19-5202791f8e2d@xxxxxxxxx/

> Ideally, KVM would probably exit with KVM_EXIT_MEMORY_FAULT, but KVM would
> need to extend run->memory_fault so that userspace knows the fault can't be
> handled.  This scenario specifically occurs when the guest has deliberately
> disabled #VEs on unaccepted memory for security purposes, i.e. the guest
> literally disabled the mechanism that tells it it screwed up.  But, because
> this is fatal, and the whole point is to NOT try to fixup the fault,
> jumping through hoops to return MEMORY_FAULT instead of SHUTDOWN doesn't
> make a whole lot of sense.
> 
> Fixes: e6a85781f783 ("KVM: TDX: Detect unexpected SEPT violations due to pending SPTEs")
> Cc: stable@xxxxxxxxxxxxxxx
> Cc: James Houghton <jthoughton@xxxxxxxxxx>
> Cc: Xiaoyao Li <xiaoyao.li@xxxxxxxxx>
> Cc: Rick Edgecombe <rick.p.edgecombe@xxxxxxxxx>
> Cc: Yan Zhao <yan.y.zhao@xxxxxxxxx>
> Cc: Binbin Wu <binbin.wu@xxxxxxxxxxxxxxx>
> Cc: Ackerley Tng <ackerleytng@xxxxxxxxxx>
> Cc: Vishal Annapurve <vannapurve@xxxxxxxxxx>
> Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
> ---
> 
> Compile tested only.
> 
>  arch/x86/kvm/vmx/tdx.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 7173ef3fc398..eb82f739a7c0 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1938,8 +1938,8 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
>  		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_make_request(KVM_REQ_TRIPLE_FAULT, vcpu);
> +			return 1;
>  		}
>  		/*
>  		 * Always treat SEPT violations as write faults.  Ignore the
> 
> base-commit: 30b5175943e709911702d8a9364145e911f57e3f