[v2][PATCH 0/2] x86/virt/tdx: Minor sparse fixups

[v2][PATCH 0/2] x86/virt/tdx: Minor sparse fixups

[Dave Hansen]

Changs from v1:

 * Add Fixes/Reviewed-by tags (Rick)
 * Add some "backwards" KVM changelog blurbs

--

Sean recently suggested relying on sparse to add type safety in TDX code,
hoping that the robots would notice and complain. Well, that plan is not
working out so great. TDX is not even sparse clean today and nobody seems
to have noticed or cared.

I can see how folks might ignore the 0 vs. NULL complaints. But the
misplaced __user is actually bad enough it should be fixed no matter
what.

Might as well fix it all up.

Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kas@kernel.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org

[v2][PATCH 1/2] x86/virt/tdx: Remove __user annotation from kernel pointer

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

Separate __user pointer variable declaration from kernel one.

There are two 'kvm_cpuid2' pointers involved here. There's an "input"
side: 'td_cpuid' which is a normal kernel pointer and an 'output'
side. The output here is userspace and there is an attempt at properly
annotating the variable with __user:

	struct kvm_cpuid2 __user *output, *td_cpuid;

But, alas, this is wrong. The __user in the definition applies to both
'output' and 'td_cpuid'. Sparse notices the address space mismatch and
will complain about it.

Fix it up by completely separating the two definitions so that it is
obviously correct without even having to know what the C syntax rules
even are.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Fixes: 488808e682e7 ("KVM: x86: Introduce KVM_TDX_GET_CPUID")
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kas@kernel.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---

 b/arch/x86/kvm/vmx/tdx.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff -puN arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-3 arch/x86/kvm/vmx/tdx.c
--- a/arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-3	2025-11-03 15:11:26.773525519 -0800
+++ b/arch/x86/kvm/vmx/tdx.c	2025-11-03 15:11:26.782526277 -0800
@@ -3054,7 +3054,8 @@ static int tdx_vcpu_get_cpuid_leaf(struc
 
 static int tdx_vcpu_get_cpuid(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
 {
-	struct kvm_cpuid2 __user *output, *td_cpuid;
+	struct kvm_cpuid2 __user *output;
+	struct kvm_cpuid2 *td_cpuid;
 	int r = 0, i = 0, leaf;
 	u32 level;
 
_

[v2][PATCH 2/2] x86/virt/tdx: Fix sparse warnings from using 0 for NULL

[Dave Hansen]

From: Dave Hansen <dave.hansen@linux.intel.com>

Stop using 0 for NULL.

sparse moans:

	... arch/x86/kvm/vmx/tdx.c:859:38: warning: Using plain integer as NULL pointer

for several TDX pointer initializations. While I love a good ptr=0
now and then, it's good to have quiet sparse builds.

Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Fixes: a50f673f25e0 ("KVM: TDX: Do TDX specific vcpu initialization")
Fixes: 8d032b683c29 ("KVM: TDX: create/destroy VM structure")
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: Xiaoyao Li <xiaoyao.li@intel.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: "Kirill A. Shutemov" <kas@kernel.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
---

 b/arch/x86/kvm/vmx/tdx.c |    6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff -puN arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-1 arch/x86/kvm/vmx/tdx.c
--- a/arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-1	2025-11-03 15:11:28.177643833 -0800
+++ b/arch/x86/kvm/vmx/tdx.c	2025-11-03 15:11:28.185644508 -0800
@@ -856,7 +856,7 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu
 	}
 	if (tdx->vp.tdvpr_page) {
 		tdx_reclaim_control_page(tdx->vp.tdvpr_page);
-		tdx->vp.tdvpr_page = 0;
+		tdx->vp.tdvpr_page = NULL;
 		tdx->vp.tdvpr_pa = 0;
 	}
 
@@ -2642,7 +2642,7 @@ free_tdcs:
 free_tdr:
 	if (tdr_page)
 		__free_page(tdr_page);
-	kvm_tdx->td.tdr_page = 0;
+	kvm_tdx->td.tdr_page = NULL;
 
 free_hkid:
 	tdx_hkid_free(kvm_tdx);
@@ -3016,7 +3016,7 @@ free_tdcx:
 free_tdvpr:
 	if (tdx->vp.tdvpr_page)
 		__free_page(tdx->vp.tdvpr_page);
-	tdx->vp.tdvpr_page = 0;
+	tdx->vp.tdvpr_page = NULL;
 	tdx->vp.tdvpr_pa = 0;
 
 	return ret;
_

Re: [v2][PATCH 1/2] x86/virt/tdx: Remove __user annotation from kernel pointer

[Kiryl Shutsemau]

On Mon, Nov 03, 2025 at 03:44:37PM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> Separate __user pointer variable declaration from kernel one.
> 
> There are two 'kvm_cpuid2' pointers involved here. There's an "input"
> side: 'td_cpuid' which is a normal kernel pointer and an 'output'
> side. The output here is userspace and there is an attempt at properly
> annotating the variable with __user:
> 
> 	struct kvm_cpuid2 __user *output, *td_cpuid;
> 
> But, alas, this is wrong. The __user in the definition applies to both
> 'output' and 'td_cpuid'. Sparse notices the address space mismatch and
> will complain about it.
> 
> Fix it up by completely separating the two definitions so that it is
> obviously correct without even having to know what the C syntax rules
> even are.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Fixes: 488808e682e7 ("KVM: x86: Introduce KVM_TDX_GET_CPUID")
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "Kirill A. Shutemov" <kas@kernel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org

Acked-by: Kiryl Shutsemau <kas@kernel.org>

-- 
 Kiryl Shutsemau / Kirill A. Shutemov

Re: [v2][PATCH 2/2] x86/virt/tdx: Fix sparse warnings from using 0 for NULL

[Kiryl Shutsemau]

On Mon, Nov 03, 2025 at 03:44:39PM -0800, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> Stop using 0 for NULL.
> 
> sparse moans:
> 
> 	... arch/x86/kvm/vmx/tdx.c:859:38: warning: Using plain integer as NULL pointer
> 
> for several TDX pointer initializations. While I love a good ptr=0
> now and then, it's good to have quiet sparse builds.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Fixes: a50f673f25e0 ("KVM: TDX: Do TDX specific vcpu initialization")
> Fixes: 8d032b683c29 ("KVM: TDX: create/destroy VM structure")
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "Kirill A. Shutemov" <kas@kernel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org

Acked-by: Kiryl Shutsemau <kas@kernel.org>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [v2][PATCH 1/2] x86/virt/tdx: Remove __user annotation from kernel pointer

[Xiaoyao Li]

On 11/4/2025 7:44 AM, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> Separate __user pointer variable declaration from kernel one.
> 
> There are two 'kvm_cpuid2' pointers involved here. There's an "input"
> side: 'td_cpuid' which is a normal kernel pointer and an 'output'
> side. The output here is userspace and there is an attempt at properly
> annotating the variable with __user:
> 
> 	struct kvm_cpuid2 __user *output, *td_cpuid;
> 
> But, alas, this is wrong. The __user in the definition applies to both
> 'output' and 'td_cpuid'. Sparse notices the address space mismatch and
> will complain about it.
> 
> Fix it up by completely separating the two definitions so that it is
> obviously correct without even having to know what the C syntax rules
> even are.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Fixes: 488808e682e7 ("KVM: x86: Introduce KVM_TDX_GET_CPUID")
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

the prefix of the shortlog is still "x86/virt/tdx". I think Sean will 
change it to "KVM: TDX:", if it gets routed through KVM tree.

Anyway,

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "Kirill A. Shutemov" <kas@kernel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
> 
>   b/arch/x86/kvm/vmx/tdx.c |    3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff -puN arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-3 arch/x86/kvm/vmx/tdx.c
> --- a/arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-3	2025-11-03 15:11:26.773525519 -0800
> +++ b/arch/x86/kvm/vmx/tdx.c	2025-11-03 15:11:26.782526277 -0800
> @@ -3054,7 +3054,8 @@ static int tdx_vcpu_get_cpuid_leaf(struc
>   
>   static int tdx_vcpu_get_cpuid(struct kvm_vcpu *vcpu, struct kvm_tdx_cmd *cmd)
>   {
> -	struct kvm_cpuid2 __user *output, *td_cpuid;
> +	struct kvm_cpuid2 __user *output;
> +	struct kvm_cpuid2 *td_cpuid;
>   	int r = 0, i = 0, leaf;
>   	u32 level;
>   
> _

Re: [v2][PATCH 2/2] x86/virt/tdx: Fix sparse warnings from using 0 for NULL

[Xiaoyao Li]

On 11/4/2025 7:44 AM, Dave Hansen wrote:
> 
> From: Dave Hansen <dave.hansen@linux.intel.com>
> 
> Stop using 0 for NULL.
> 
> sparse moans:
> 
> 	... arch/x86/kvm/vmx/tdx.c:859:38: warning: Using plain integer as NULL pointer
> 
> for several TDX pointer initializations. While I love a good ptr=0
> now and then, it's good to have quiet sparse builds.
> 
> Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> Fixes: a50f673f25e0 ("KVM: TDX: Do TDX specific vcpu initialization")
> Fixes: 8d032b683c29 ("KVM: TDX: create/destroy VM structure")
> Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>

> Cc: Xiaoyao Li <xiaoyao.li@intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> Cc: Paolo Bonzini <pbonzini@redhat.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: "Kirill A. Shutemov" <kas@kernel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: kvm@vger.kernel.org
> Cc: linux-kernel@vger.kernel.org
> ---
> 
>   b/arch/x86/kvm/vmx/tdx.c |    6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff -puN arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-1 arch/x86/kvm/vmx/tdx.c
> --- a/arch/x86/kvm/vmx/tdx.c~tdx-sparse-fix-1	2025-11-03 15:11:28.177643833 -0800
> +++ b/arch/x86/kvm/vmx/tdx.c	2025-11-03 15:11:28.185644508 -0800
> @@ -856,7 +856,7 @@ void tdx_vcpu_free(struct kvm_vcpu *vcpu
>   	}
>   	if (tdx->vp.tdvpr_page) {
>   		tdx_reclaim_control_page(tdx->vp.tdvpr_page);
> -		tdx->vp.tdvpr_page = 0;
> +		tdx->vp.tdvpr_page = NULL;
>   		tdx->vp.tdvpr_pa = 0;
>   	}
>   
> @@ -2642,7 +2642,7 @@ free_tdcs:
>   free_tdr:
>   	if (tdr_page)
>   		__free_page(tdr_page);
> -	kvm_tdx->td.tdr_page = 0;
> +	kvm_tdx->td.tdr_page = NULL;
>   
>   free_hkid:
>   	tdx_hkid_free(kvm_tdx);
> @@ -3016,7 +3016,7 @@ free_tdcx:
>   free_tdvpr:
>   	if (tdx->vp.tdvpr_page)
>   		__free_page(tdx->vp.tdvpr_page);
> -	tdx->vp.tdvpr_page = 0;
> +	tdx->vp.tdvpr_page = NULL;
>   	tdx->vp.tdvpr_pa = 0;
>   
>   	return ret;
> _

Re: [v2][PATCH 1/2] x86/virt/tdx: Remove __user annotation from kernel pointer

[Sean Christopherson]

On Tue, Nov 04, 2025, Xiaoyao Li wrote:
> On 11/4/2025 7:44 AM, Dave Hansen wrote:
> > 
> > From: Dave Hansen <dave.hansen@linux.intel.com>
> > 
> > Separate __user pointer variable declaration from kernel one.
> > 
> > There are two 'kvm_cpuid2' pointers involved here. There's an "input"
> > side: 'td_cpuid' which is a normal kernel pointer and an 'output'
> > side. The output here is userspace and there is an attempt at properly
> > annotating the variable with __user:
> > 
> > 	struct kvm_cpuid2 __user *output, *td_cpuid;
> > 
> > But, alas, this is wrong. The __user in the definition applies to both
> > 'output' and 'td_cpuid'. Sparse notices the address space mismatch and
> > will complain about it.
> > 
> > Fix it up by completely separating the two definitions so that it is
> > obviously correct without even having to know what the C syntax rules
> > even are.
> > 
> > Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
> > Fixes: 488808e682e7 ("KVM: x86: Introduce KVM_TDX_GET_CPUID")
> > Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> 
> the prefix of the shortlog is still "x86/virt/tdx". I think Sean will change
> it to "KVM: TDX:", if it gets routed through KVM tree.

Ya, I'll fixup when applying.

Re: [v2][PATCH 0/2] x86/virt/tdx: Minor sparse fixups

[Sean Christopherson]

On Mon, 03 Nov 2025 15:44:35 -0800, Dave Hansen wrote:
> Changs from v1:
> 
>  * Add Fixes/Reviewed-by tags (Rick)
>  * Add some "backwards" KVM changelog blurbs
> 
> --
> 
> [...]

Applied to kvm-x86 tdx, with the scopes changed to "KVM: TDX:".  Thanks!

[1/2] KVM: TDX: Remove __user annotation from kernel pointer
      https://github.com/kvm-x86/linux/commit/228add34dc2f
[2/2] KVM: TDX: Fix sparse warnings from using 0 for NULL
      https://github.com/kvm-x86/linux/commit/27376465e945

--
https://github.com/kvm-x86/linux/tree/next