linux-kernel - Re: [PATCH v9 17/22] KVM: x86: Advertise support for FRED

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Message-ID: <aRQ3ngRvif/0QRTC@intel.com>
Date: Wed, 12 Nov 2025 15:30:38 +0800
From: Chao Gao <chao.gao@...el.com>
To: "Xin Li (Intel)" <xin@...or.com>
CC: <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <pbonzini@...hat.com>, <seanjc@...gle.com>,
	<corbet@....net>, <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>, <hpa@...or.com>,
	<luto@...nel.org>, <peterz@...radead.org>, <andrew.cooper3@...rix.com>,
	<hch@...radead.org>, <sohil.mehta@...el.com>
Subject: Re: [PATCH v9 17/22] KVM: x86: Advertise support for FRED

On Sun, Oct 26, 2025 at 01:19:05PM -0700, Xin Li (Intel) wrote:
>From: Xin Li <xin3.li@...el.com>
>
>Advertise support for FRED to userspace after changes required to enable
>FRED in a KVM guest are in place.

I'm not sure if AMD CPUs support FRED, but just in case, we can clear FRED
i.e., kvm_cpu_cap_clear(X86_FEATURE_FRED) in svm_set_cpu_caps().

With this fixed:

Reviewed-by: Chao Gao <chao.gao@...el.com>

>
>Signed-off-by: Xin Li <xin3.li@...el.com>
>Signed-off-by: Xin Li (Intel) <xin@...or.com>
>Tested-by: Shan Kang <shan.kang@...el.com>
>Tested-by: Xuelian Guo <xuelian.guo@...el.com>
>---
>
>Change in v5:
>* Don't advertise FRED/LKGS together, LKGS can be advertised as an
>  independent feature (Sean).
>* Add TB from Xuelian Guo.
>---
> arch/x86/kvm/cpuid.c | 1 +
> 1 file changed, 1 insertion(+)
>
>diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
>index d563a948318b..0bf97b8a3216 100644
>--- a/arch/x86/kvm/cpuid.c
>+++ b/arch/x86/kvm/cpuid.c
>@@ -1014,6 +1014,7 @@ void kvm_set_cpu_caps(void)
> 		F(FSRS),
> 		F(FSRC),
> 		F(WRMSRNS),
>+		X86_64_F(FRED),
> 		X86_64_F(LKGS),
> 		F(AMX_FP16),
> 		F(AVX_IFMA),
>-- 
>2.51.0
>