linux-kernel - [PATCH v6 13/25] KVM: x86: Initialize kvm_caps.supported

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Message-Id: <20230914063325.85503-14-weijiang.yang@intel.com>
Date:   Thu, 14 Sep 2023 02:33:13 -0400
From:   Yang Weijiang <weijiang.yang@...el.com>
To:     seanjc@...gle.com, pbonzini@...hat.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Cc:     dave.hansen@...el.com, peterz@...radead.org, chao.gao@...el.com,
        rick.p.edgecombe@...el.com, weijiang.yang@...el.com,
        john.allen@....com
Subject: [PATCH v6 13/25] KVM: x86: Initialize kvm_caps.supported_xss

Set original kvm_caps.supported_xss to (host_xss & KVM_SUPPORTED_XSS) if
XSAVES is supported. host_xss contains the host supported xstate feature
bits for thread FPU context switch, KVM_SUPPORTED_XSS includes all KVM
enabled XSS feature bits, the resulting value represents the supervisor
xstates that are available to guest and are backed by host FPU framework
for swapping {guest,host} XSAVE-managed registers/MSRs.

Signed-off-by: Yang Weijiang <weijiang.yang@...el.com>
---
 arch/x86/kvm/x86.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 9a616d84bd39..66edbed25db8 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -226,6 +226,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
 				| XFEATURE_MASK_PKRU | XFEATURE_MASK_XTILE)
 
+#define KVM_SUPPORTED_XSS     0
+
 u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
 
@@ -9515,12 +9517,13 @@ static int __kvm_x86_vendor_init(struct kvm_x86_init_ops *ops)
 		host_xcr0 = xgetbv(XCR_XFEATURE_ENABLED_MASK);
 		kvm_caps.supported_xcr0 = host_xcr0 & KVM_SUPPORTED_XCR0;
 	}
+	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
+		rdmsrl(MSR_IA32_XSS, host_xss);
+		kvm_caps.supported_xss = host_xss & KVM_SUPPORTED_XSS;
+	}
 
 	rdmsrl_safe(MSR_EFER, &host_efer);
 
-	if (boot_cpu_has(X86_FEATURE_XSAVES))
-		rdmsrl(MSR_IA32_XSS, host_xss);
-
 	kvm_init_pmu_capability(ops->pmu_ops);
 
 	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
-- 
2.27.0