linux-kernel - Re: [RFC PATCH 06/12] KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG

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Message-ID: <aK7EQH44UOr46Hdx@yzhao56-desk.sh.intel.com>
Date: Wed, 27 Aug 2025 16:39:28 +0800
From: Yan Zhao <yan.y.zhao@...el.com>
To: Sean Christopherson <seanjc@...gle.com>
CC: Paolo Bonzini <pbonzini@...hat.com>, <kvm@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, Michael Roth <michael.roth@....com>, "Ira
 Weiny" <ira.weiny@...el.com>, Vishal Annapurve <vannapurve@...gle.com>, "Rick
 Edgecombe" <rick.p.edgecombe@...el.com>
Subject: Re: [RFC PATCH 06/12] KVM: TDX: Return -EIO, not -EINVAL, on a
 KVM_BUG_ON() condition

On Tue, Aug 26, 2025 at 05:05:16PM -0700, Sean Christopherson wrote:
> Return -EIO when a KVM_BUG_ON() is tripped, as KVM's ABI is to return -EIO
> when a VM has been killed due to a KVM bug, not -EINVAL.
Looks good to me, though currently the "-EIO" will not be returned to userspace
either. In the fault path, RET_PF_RETRY is returned instead, while in the zap
paths, void is returned.

> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>  arch/x86/kvm/vmx/tdx.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index 9fb6e5f02cc9..ef4ffcad131f 100644
> --- a/arch/x86/kvm/vmx/tdx.c
> +++ b/arch/x86/kvm/vmx/tdx.c
> @@ -1624,7 +1624,7 @@ static int tdx_mem_page_record_premap_cnt(struct kvm *kvm, gfn_t gfn,
>  	struct kvm_tdx *kvm_tdx = to_kvm_tdx(kvm);
>  
>  	if (KVM_BUG_ON(kvm->arch.pre_fault_allowed, kvm))
> -		return -EINVAL;
> +		return -EIO;
>  
>  	/* nr_premapped will be decreased when tdh_mem_page_add() is called. */
>  	atomic64_inc(&kvm_tdx->nr_premapped);
> @@ -1638,7 +1638,7 @@ static int tdx_sept_set_private_spte(struct kvm *kvm, gfn_t gfn,
>  
>  	/* TODO: handle large pages. */
>  	if (KVM_BUG_ON(level != PG_LEVEL_4K, kvm))
> -		return -EINVAL;
> +		return -EIO;
>  
>  	/*
>  	 * Read 'pre_fault_allowed' before 'kvm_tdx->state'; see matching
> @@ -1849,7 +1849,7 @@ static int tdx_sept_free_private_spt(struct kvm *kvm, gfn_t gfn,
>  	 * and slot move/deletion.
>  	 */
>  	if (KVM_BUG_ON(is_hkid_assigned(kvm_tdx), kvm))
> -		return -EINVAL;
> +		return -EIO;
>  
>  	/*
>  	 * The HKID assigned to this TD was already freed and cache was
> @@ -1870,7 +1870,7 @@ static int tdx_sept_remove_private_spte(struct kvm *kvm, gfn_t gfn,
>  	 * there can't be anything populated in the private EPT.
>  	 */
>  	if (KVM_BUG_ON(!is_hkid_assigned(to_kvm_tdx(kvm)), kvm))
> -		return -EINVAL;
> +		return -EIO;
>  
>  	ret = tdx_sept_zap_private_spte(kvm, gfn, level, page);
>  	if (ret <= 0)
> -- 
> 2.51.0.268.g9569e192d0-goog
>