[PATCH v4 10/11] KVM: x86: Refine the matching and clearing logic for supported_xss

[Like Xu]

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 <sea...@google.com>
Signed-off-by: Like Xu <like...@linux.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 03c0faf16a7d..14ed3251376f 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7302,9 +7302,10 @@ 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 */
        if (!cpu_has_vmx_rdtscp())
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 4bcf5b130e38..171605dcbd65 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -205,6 +205,8 @@ 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);
 
@@ -10450,8 +10452,10 @@ 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)
-- 
2.29.2