[PATCH] kvm: x86: refine kvm_get_arch_capabilities()

[Xiaoyao Li <xiaoyao.li@xxxxxxxxxxxxxxx>]

1. Using X86_FEATURE_ARCH_CAPABILITIES to enumerate the existence of
MSR_IA32_ARCH_CAPABILITIES to avoid using rdmsrl_safe().

2. Since kvm_get_arch_capabilities() is only used in this file, making
it static.

Signed-off-by: Xiaoyao Li <xiaoyao.li@xxxxxxxxxxxxxxx>
---
 arch/x86/include/asm/kvm_host.h | 1 -
 arch/x86/kvm/x86.c              | 8 ++++----
 2 files changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index a9d03af34030..d4ae67870764 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1526,7 +1526,6 @@ int kvm_pv_send_ipi(struct kvm *kvm, unsigned long ipi_bitmap_low,
 		    unsigned long ipi_bitmap_high, u32 min,
 		    unsigned long icr, int op_64_bit);
 
-u64 kvm_get_arch_capabilities(void);
 void kvm_define_shared_msr(unsigned index, u32 msr);
 int kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
 
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a0d1fc80ac5a..ba8e269a8cd2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1205,11 +1205,12 @@ static u32 msr_based_features[] = {
 
 static unsigned int num_msr_based_features;
 
-u64 kvm_get_arch_capabilities(void)
+static u64 kvm_get_arch_capabilities(void)
 {
-	u64 data;
+	u64 data = 0;
 
-	rdmsrl_safe(MSR_IA32_ARCH_CAPABILITIES, &data);
+	if (boot_cpu_has(X86_FEATURE_ARCH_CAPABILITIES))
+		rdmsrl(MSR_IA32_ARCH_CAPABILITIES, data);
 
 	/*
 	 * If we're doing cache flushes (either "always" or "cond")
@@ -1225,7 +1226,6 @@ u64 kvm_get_arch_capabilities(void)
 
 	return data;
 }
-EXPORT_SYMBOL_GPL(kvm_get_arch_capabilities);
 
 static int kvm_get_msr_feature(struct kvm_msr_entry *msr)
 {
-- 
2.19.1