linux-kernel - Re: [RFC PATCH v2 06/18] KVM: TDX: Return -EIO, not -EINVAL, on a KVM_BUG

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Message-ID: <506f90ed-ff2b-49f9-b1c3-4fb84577dbee@linux.intel.com>
Date: Fri, 29 Aug 2025 17:40:01 +0800
From: Binbin Wu <binbin.wu@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
 Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
 Ira Weiny <ira.weiny@...el.com>, Kai Huang <kai.huang@...el.com>,
 Michael Roth <michael.roth@....com>, Yan Zhao <yan.y.zhao@...el.com>,
 Vishal Annapurve <vannapurve@...gle.com>,
 Rick Edgecombe <rick.p.edgecombe@...el.com>,
 Ackerley Tng <ackerleytng@...gle.com>
Subject: Re: [RFC PATCH v2 06/18] KVM: TDX: Return -EIO, not -EINVAL, on a
 KVM_BUG_ON() condition



On 8/29/2025 8:06 AM, 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.  Note, many (all?)
> of the affected paths never propagate the error code to userspace, i.e.
> this is about internal consistency more than anything else.
>
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>

Reviewed-by: Binbin Wu <binbin.wu@...ux.intel.com>

> ---
>   arch/x86/kvm/vmx/tdx.c | 12 ++++++------
>   1 file changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
> index f24f8635b433..50a9d81dad53 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
> @@ -1661,10 +1661,10 @@ static int tdx_sept_drop_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;
>   
>   	if (KVM_BUG_ON(!is_hkid_assigned(kvm_tdx), kvm))
> -		return -EINVAL;
> +		return -EIO;
>   
>   	/*
>   	 * When zapping private page, write lock is held. So no race condition
> @@ -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)