[PATCH v5 10/13] KVM: x86: Refine the matching and clearing logic for supported_xss

[Yang Weijiang]

From: Like Xu <like.xu@xxxxxxxxxxxxxxx>

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@xxxxxxxxxx>
Signed-off-by: Like Xu <like.xu@xxxxxxxxxxxxxxx>
Signed-off-by: Yang Weijiang <weijiang.yang@xxxxxxxxx>
---
 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 2d23c0296611..636c50b95038 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7349,9 +7349,10 @@ 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 c225260c949e..2424d475a4d7 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);
 
@@ -10654,8 +10656,10 @@ 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)
-- 
2.21.1