KVM: x86/tdx: Do not print error message on non-present feature

[PATCH] KVM: x86/tdx: Do not print error message on non-present feature

Posted by Jiri Slaby (SUSE) 3 weeks, 3 days ago

Before commit 165e77353831 below, the kernel did not print anything when
X86_FEATURE_TDX_HOST_PLATFORM was not present in a cpu.

After the commit, this is emitted to the log, with the error level:
virt/tdx: TDX not supported by the host platform

This is disturbing as it is not an error running CPUs without the
feature.

Drop the error message completely to revert to the state before
165e77353831.

Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
Fixes: 165e77353831 ("KVM: x86/tdx: Do VMXON and TDX-Module initialization during subsys init")
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Chao Gao <chao.gao@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Sean Christopherson <seanjc@google.com>

--

Cc: Thomas Gleixner <tglx@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Kiryl Shutsemau <kas@kernel.org>
Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
Cc: linux-kernel@vger.kernel.org
Cc: linux-coco@lists.linux.dev
Cc: kvm@vger.kernel.org
---
 arch/x86/virt/vmx/tdx/tdx.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 42df8ea464c4..bdfc3bf12a9c 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1228,10 +1228,8 @@ static __init int tdx_enable(void)
 	enum cpuhp_state state;
 	int ret;
 
-	if (!cpu_feature_enabled(X86_FEATURE_TDX_HOST_PLATFORM)) {
-		pr_err("TDX not supported by the host platform\n");
+	if (!cpu_feature_enabled(X86_FEATURE_TDX_HOST_PLATFORM))
 		return -ENODEV;
-	}
 
 	if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) {
 		pr_err("XSAVE is required for TDX\n");
-- 
2.54.0

Re: [PATCH] KVM: x86/tdx: Do not print error message on non-present feature

Posted by Edgecombe, Rick P 2 weeks, 5 days ago

On Thu, 2026-07-02 at 06:32 +0200, Jiri Slaby (SUSE) wrote:
> Before commit 165e77353831 below, the kernel did not print anything when
> X86_FEATURE_TDX_HOST_PLATFORM was not present in a cpu.

This isn't quite correct. It would print something if KVM tried to enable it,
which is controlled by a module param.

> 
> After the commit, this is emitted to the log, with the error level:
> virt/tdx: TDX not supported by the host platform
> 
> This is disturbing as it is not an error running CPUs without the
> feature.

Agree. If the kernel is now trying to enabling TDX automatically, it is not
error print worthy if it fails because TDX is not supported.

But after the below change, something is still printed if the kernel param is
used. Can we be a little more specific?

> 
> Drop the error message completely to revert to the state before
> 165e77353831.

'state' is a little ambiguous here. Sounds like a full revert.

> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
> Fixes: 165e77353831 ("KVM: x86/tdx: Do VMXON and TDX-Module initialization during subsys init")
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Chao Gao <chao.gao@intel.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Sean Christopherson <seanjc@google.com>
> 
> --
> 
> Cc: Thomas Gleixner <tglx@kernel.org>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: x86@kernel.org
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Kiryl Shutsemau <kas@kernel.org>
> Cc: Rick Edgecombe <rick.p.edgecombe@intel.com>
> Cc: linux-kernel@vger.kernel.org
> Cc: linux-coco@lists.linux.dev
> Cc: kvm@vger.kernel.org
> ---
>  arch/x86/virt/vmx/tdx/tdx.c | 4 +---
>  1 file changed, 1 insertion(+), 3 deletions(-)
> 
> diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
> index 42df8ea464c4..bdfc3bf12a9c 100644
> --- a/arch/x86/virt/vmx/tdx/tdx.c
> +++ b/arch/x86/virt/vmx/tdx/tdx.c
> @@ -1228,10 +1228,8 @@ static __init int tdx_enable(void)
>  	enum cpuhp_state state;
>  	int ret;
>  
> -	if (!cpu_feature_enabled(X86_FEATURE_TDX_HOST_PLATFORM)) {
> -		pr_err("TDX not supported by the host platform\n");
> +	if (!cpu_feature_enabled(X86_FEATURE_TDX_HOST_PLATFORM))
>  		return -ENODEV;
> -	}

Seems like a reasonable change to me, but the log is a bit misleading.

>  
>  	if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) {
>  		pr_err("XSAVE is required for TDX\n");

Re: [PATCH] KVM: x86/tdx: Do not print error message on non-present feature

Posted by Kiryl Shutsemau 3 weeks, 3 days ago

On Thu, Jul 02, 2026 at 06:32:04AM +0200, Jiri Slaby (SUSE) wrote:
> Before commit 165e77353831 below, the kernel did not print anything when
> X86_FEATURE_TDX_HOST_PLATFORM was not present in a cpu.
> 
> After the commit, this is emitted to the log, with the error level:
> virt/tdx: TDX not supported by the host platform
> 
> This is disturbing as it is not an error running CPUs without the
> feature.
> 
> Drop the error message completely to revert to the state before
> 165e77353831.
> 
> Signed-off-by: Jiri Slaby (SUSE) <jirislaby@kernel.org>
> Fixes: 165e77353831 ("KVM: x86/tdx: Do VMXON and TDX-Module initialization during subsys init")
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Chao Gao <chao.gao@intel.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Sean Christopherson <seanjc@google.com>

Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>

-- 
  Kiryl Shutsemau / Kirill A. Shutemov