linux-kernel - [RESEND PATCH v4 09/10] KVM: x86: Refine the matching and clearing logic for supported

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Date:   Mon, 10 May 2021 16:15:33 +0800
From:   Like Xu <like.xu@...ux.intel.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, weijiang.yang@...el.com,
        wei.w.wang@...el.com, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [RESEND PATCH v4 09/10] KVM: x86: Refine the matching and clearing logic for supported_xss

Refine the code path of the existing clearing of supported_xss in this way:
initialize the supported_xss with the filter of KVM_SUPPORTED_XSS mask and
update its value in a bit clear manner (rather than bit setting).

Suggested-by: Sean Christopherson <seanjc@...gle.com>
Signed-off-by: Like Xu <like.xu@...ux.intel.com>
---
 arch/x86/kvm/vmx/vmx.c | 5 +++--
 arch/x86/kvm/x86.c     | 6 +++++-
 2 files changed, 8 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index f88c6e8f7a3a..d080bf163565 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7384,9 +7384,10 @@ static __init void vmx_set_cpu_caps(void)
 		kvm_cpu_cap_set(X86_FEATURE_UMIP);
 
 	/* CPUID 0xD.1 */
-	supported_xss = 0;
-	if (!cpu_has_vmx_xsaves())
+	if (!cpu_has_vmx_xsaves()) {
 		kvm_cpu_cap_clear(X86_FEATURE_XSAVES);
+		supported_xss = 0;
+	}
 
 	/* CPUID 0x80000001 and 0x7 (RDPID) */
 	if (!cpu_has_vmx_rdtscp()) {
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b699f7a37b1a..3a32bea2277e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -203,6 +203,8 @@ static struct kvm_user_return_msrs __percpu *user_return_msrs;
 				| XFEATURE_MASK_BNDCSR | XFEATURE_MASK_AVX512 \
 				| XFEATURE_MASK_PKRU)
 
+#define KVM_SUPPORTED_XSS     0
+
 u64 __read_mostly host_efer;
 EXPORT_SYMBOL_GPL(host_efer);
 
@@ -10619,8 +10621,10 @@ int kvm_arch_hardware_setup(void *opaque)
 
 	rdmsrl_safe(MSR_EFER, &host_efer);
 
-	if (boot_cpu_has(X86_FEATURE_XSAVES))
+	if (boot_cpu_has(X86_FEATURE_XSAVES)) {
 		rdmsrl(MSR_IA32_XSS, host_xss);
+		supported_xss = host_xss & KVM_SUPPORTED_XSS;
+	}
 
 	r = ops->hardware_setup();
 	if (r != 0)
-- 
2.31.1