[PATCH 3.13 008/140] x86, kvm: cache the base of the KVM cpuid leaves

Greg Kroah-Hartman
2014-02-04T21:51:33Z

From: Paolo Bonzini <pbonzini@redhat.com>

commit 1c300a40772dae829b91dad634999a6a522c0829 upstream.

It is unnecessary to go through hypervisor_cpuid_base every time
a leaf is found (which will be every time a feature is requested
after the next patch).

Fixes: 1085ba7f552d84aa8ac0ae903fa8d0cc2ff9f79d
Cc: mtosatti@redhat.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/include/asm/kvm_para.h | 22 ++++++----------------
arch/x86/kernel/kvm.c | 27 +++++++++++++++++++++++++++
2 files changed, 33 insertions(+), 16 deletions(-)

--- a/arch/x86/include/asm/kvm_para.h
+++ b/arch/x86/include/asm/kvm_para.h
@@ -85,28 +85,13 @@ static inline long kvm_hypercall4(unsign
return ret;
}

-static inline uint32_t kvm_cpuid_base(void)
-{
- if (boot_cpu_data.cpuid_level < 0)
- return 0; /* So we don't blow up on old processors */
-
- if (cpu_has_hypervisor)
- return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
-
- return 0;
-}
-
-static inline bool kvm_para_available(void)
-{
- return kvm_cpuid_base() != 0;
-}
-
static inline unsigned int kvm_arch_para_features(void)
{
return cpuid_eax(KVM_CPUID_FEATURES);
}

#ifdef CONFIG_KVM_GUEST
+bool kvm_para_available(void);
void __init kvm_guest_init(void);
void kvm_async_pf_task_wait(u32 token);
void kvm_async_pf_task_wake(u32 token);
@@ -126,6 +111,11 @@ static inline void kvm_spinlock_init(voi
#define kvm_async_pf_task_wait(T) do {} while(0)
#define kvm_async_pf_task_wake(T) do {} while(0)

+static inline bool kvm_para_available(void)
+{
+ return 0;
+}
+
static inline u32 kvm_read_and_reset_pf_reason(void)
{
return 0;
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -500,6 +500,33 @@ void __init kvm_guest_init(void)
#endif
}

+static noinline uint32_t __kvm_cpuid_base(void)
+{
+ if (boot_cpu_data.cpuid_level < 0)
+ return 0; /* So we don't blow up on old processors */
+
+ if (cpu_has_hypervisor)
+ return hypervisor_cpuid_base("KVMKVMKVM\0\0\0", 0);
+
+ return 0;
+}
+
+static inline uint32_t kvm_cpuid_base(void)
+{
+ static int kvm_cpuid_base = -1;
+
+ if (kvm_cpuid_base == -1)
+ kvm_cpuid_base = __kvm_cpuid_base();
+
+ return kvm_cpuid_base;
+}
+
+bool kvm_para_available(void)
+{
+ return kvm_cpuid_base() != 0;
+}
+EXPORT_SYMBOL_GPL(kvm_para_available);
+
static uint32_t __init kvm_detect(void)
{
return kvm_cpuid_base();