[PATCH v8 05/12] perf/x86/intel/pt: Introduce a new function to get capability of Intel PT

[Luwei Kang]

New function pt_cap_decode() will be invoked in KVM to check
if a specific capability is available in KVM guest.
Another function pt_cap_get() can only check the hardware
capabilities but this may different with KVM guest because
some features may not be exposed to guest.

Signed-off-by: Luwei Kang <luwei.kang@xxxxxxxxx>
---
 arch/x86/events/intel/pt.c      | 10 ++++++++--
 arch/x86/include/asm/intel_pt.h |  2 ++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/arch/x86/events/intel/pt.c b/arch/x86/events/intel/pt.c
index f65f97a..18a2e80 100644
--- a/arch/x86/events/intel/pt.c
+++ b/arch/x86/events/intel/pt.c
@@ -76,14 +76,20 @@
 	PT_CAP(psb_periods,		1, CPUID_EBX, 0xffff0000),
 };
 
-u32 pt_cap_get(enum pt_capabilities cap)
+u32 pt_cap_decode(u32 *caps, enum pt_capabilities cap)
 {
 	struct pt_cap_desc *cd = &pt_caps[cap];
-	u32 c = pt_pmu.caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
+	u32 c = caps[cd->leaf * PT_CPUID_REGS_NUM + cd->reg];
 	unsigned int shift = __ffs(cd->mask);
 
 	return (c & cd->mask) >> shift;
 }
+EXPORT_SYMBOL_GPL(pt_cap_decode);
+
+u32 pt_cap_get(enum pt_capabilities cap)
+{
+	return pt_cap_decode(pt_pmu.caps, cap);
+}
 EXPORT_SYMBOL_GPL(pt_cap_get);
 
 static ssize_t pt_cap_show(struct device *cdev,
diff --git a/arch/x86/include/asm/intel_pt.h b/arch/x86/include/asm/intel_pt.h
index 2de4db0..9c71453 100644
--- a/arch/x86/include/asm/intel_pt.h
+++ b/arch/x86/include/asm/intel_pt.h
@@ -27,9 +27,11 @@ enum pt_capabilities {
 #if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
 void cpu_emergency_stop_pt(void);
 extern u32 pt_cap_get(enum pt_capabilities cap);
+extern u32 pt_cap_decode(u32 *caps, enum pt_capabilities cap);
 #else
 static inline void cpu_emergency_stop_pt(void) {}
 static inline u32 pt_cap_get(enum pt_capabilities cap) { return 0; }
+static u32 pt_cap_decode(u32 *caps, enum pt_capabilities cap) { return 0; }
 #endif
 
 #endif /* _ASM_X86_INTEL_PT_H */
-- 
1.8.3.1