[PATCH] KVM: x86/cpuid: Clear XFD for component i if the base feature is missing

From: Like Xu <like.xu.linux@gmail.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jing Liu <jing2.liu@intel.com>,
	Sean Christopherson <seanjc@google.com>,
	Jim Mattson <jmattson@google.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Joerg Roedel <joro@8bytes.org>,
	kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] KVM: x86/cpuid: Clear XFD for component i if the base feature is missing
Date: Mon, 17 Jan 2022 15:45:31 +0800	[thread overview]
Message-ID: <20220117074531.76925-1-likexu@tencent.com> (raw)

From: Like Xu <likexu@tencent.com>

According to Intel extended feature disable (XFD) spec, the sub-function i
(i > 1) of CPUID function 0DH enumerates "details for state component i.
ECX[2] enumerates support for XFD support for this state component."

If KVM does not report F(XFD) feature (e.g. due to CONFIG_X86_64),
then the corresponding XFD support for any state component i
should also be removed. Translate this dependency into KVM terms.

Fixes: 690a757d610e ("kvm: x86: Add CPUID support for Intel AMX")
Signed-off-by: Like Xu <likexu@tencent.com>
---
 arch/x86/kvm/cpuid.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index c55e57b30e81..e96efef4f048 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -886,6 +886,9 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 				--array->nent;
 				continue;
 			}
+
+			if (!kvm_cpu_cap_has(X86_FEATURE_XFD))
+				entry->ecx &= ~BIT_ULL(2);
 			entry->edx = 0;
 		}
 		break;
-- 
2.33.1

