Re: [PATCH V3 01/23] perf/x86: Support outputting XMM registers

From: Liang, Kan
Date: Tue Mar 26 2019 - 09:15:03 EST



On 3/25/2019 8:11 PM, Thomas Gleixner wrote:
On Fri, 22 Mar 2019, kan.liang@xxxxxxxxxxxxxxx wrote:

+ PERF_REG_X86_XMM15 = 62,
+
+ /* All registers include the XMMX registers */
+ PERF_REG_X86_MAX = PERF_REG_X86_XMM15 + 2,

Ergo: PERF_REG_X86_MAX == 64

-#define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
+#define REG_RESERVED \
+ (PERF_REG_X86_MAX == 64 ? 0 : ~((1ULL << PERF_REG_X86_MAX)) - 1ULL)

So what the heck is this conditional for?

But now 32bit has also access to the upper 8 GPRs simply because
REG_RESERVED is now 0 and REG_NOSUPPORT is not excluding them either.


The patch as below fixes the name issue, removes unnecessary check for REG_RESERVED, and adds REG_NOSUPPORT for 32bit to exclude unsupported registers.

I will also change the user space patch accordingly and send out the V4.

Thanks,
Kan

------

diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
index e2b1447192a8..9378c6b2128f 100644
--- a/arch/x86/events/core.c
+++ b/arch/x86/events/core.c
@@ -560,6 +560,16 @@ int x86_pmu_hw_config(struct perf_event *event)
return -EINVAL;
}

+ if (event->attr.sample_regs_user & ~PEBS_REGS)
+ return -EINVAL;
+ /*
+ * Besides the general purpose registers, XMM registers may
+ * be collected in PEBS on some platforms, e.g. Icelake
+ */
+ if ((event->attr.sample_regs_intr & ~PEBS_REGS) &&
+ (!x86_pmu.has_xmm_regs || !event->attr.precise_ip))
+ return -EINVAL;
+
return x86_setup_perfctr(event);
}

diff --git a/arch/x86/events/perf_event.h b/arch/x86/events/perf_event.h
index a75955741c50..6428941a5073 100644
--- a/arch/x86/events/perf_event.h
+++ b/arch/x86/events/perf_event.h
@@ -657,6 +657,8 @@ struct x86_pmu {
* Check period value for PERF_EVENT_IOC_PERIOD ioctl.
*/
int (*check_period) (struct perf_event *event, u64 period);
+
+ unsigned int has_xmm_regs : 1; /* support XMM regs */
};

struct x86_perf_task_context {
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 8bdf74902293..d9f5bbe44b3c 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -248,6 +248,11 @@ extern void perf_events_lapic_init(void);
#define PERF_EFLAGS_VM (1UL << 5)

struct pt_regs;
+struct x86_perf_regs {
+ struct pt_regs regs;
+ u64 *xmm_regs;
+};
+
extern unsigned long perf_instruction_pointer(struct pt_regs *regs);
extern unsigned long perf_misc_flags(struct pt_regs *regs);
#define perf_misc_flags(regs) perf_misc_flags(regs)
diff --git a/arch/x86/include/uapi/asm/perf_regs.h b/arch/x86/include/uapi/asm/perf_regs.h
index f3329cabce5c..ac67bbea10ca 100644
--- a/arch/x86/include/uapi/asm/perf_regs.h
+++ b/arch/x86/include/uapi/asm/perf_regs.h
@@ -27,8 +27,29 @@ enum perf_event_x86_regs {
PERF_REG_X86_R13,
PERF_REG_X86_R14,
PERF_REG_X86_R15,
-
+ /* These are the limits for the GPRs. */
PERF_REG_X86_32_MAX = PERF_REG_X86_GS + 1,
PERF_REG_X86_64_MAX = PERF_REG_X86_R15 + 1,
+
+ /* These all need two bits set because they are 128bit */
+ PERF_REG_X86_XMM0 = 32,
+ PERF_REG_X86_XMM1 = 34,
+ PERF_REG_X86_XMM2 = 36,
+ PERF_REG_X86_XMM3 = 38,
+ PERF_REG_X86_XMM4 = 40,
+ PERF_REG_X86_XMM5 = 42,
+ PERF_REG_X86_XMM6 = 44,
+ PERF_REG_X86_XMM7 = 46,
+ PERF_REG_X86_XMM8 = 48,
+ PERF_REG_X86_XMM9 = 50,
+ PERF_REG_X86_XMM10 = 52,
+ PERF_REG_X86_XMM11 = 54,
+ PERF_REG_X86_XMM12 = 56,
+ PERF_REG_X86_XMM13 = 58,
+ PERF_REG_X86_XMM14 = 60,
+ PERF_REG_X86_XMM15 = 62,
+
+ /* These include both GPRs and XMMX registers */
+ PERF_REG_X86_XMM_MAX = PERF_REG_X86_XMM15 + 2,
};
#endif /* _ASM_X86_PERF_REGS_H */
diff --git a/arch/x86/kernel/perf_regs.c b/arch/x86/kernel/perf_regs.c
index c06c4c16c6b6..9e2f6be1e770 100644
--- a/arch/x86/kernel/perf_regs.c
+++ b/arch/x86/kernel/perf_regs.c
@@ -59,20 +59,41 @@ static unsigned int pt_regs_offset[PERF_REG_X86_MAX] = {

u64 perf_reg_value(struct pt_regs *regs, int idx)
{
+ struct x86_perf_regs *perf_regs;
+
+ if (idx >= PERF_REG_X86_XMM0 && idx < PERF_REG_X86_XMM_MAX) {
+ perf_regs = container_of(regs, struct x86_perf_regs, regs);
+ if (!perf_regs->xmm_regs)
+ return 0;
+ return perf_regs->xmm_regs[idx - PERF_REG_X86_XMM0];
+ }
+
if (WARN_ON_ONCE(idx >= ARRAY_SIZE(pt_regs_offset)))
return 0;

return regs_get_register(regs, pt_regs_offset[idx]);
}

-#define REG_RESERVED (~((1ULL << PERF_REG_X86_MAX) - 1ULL))
+#define REG_RESERVED 0

#ifdef CONFIG_X86_32
+#define REG_NOSUPPORT ((1ULL << PERF_REG_X86_R8) | \
+ (1ULL << PERF_REG_X86_R9) | \
+ (1ULL << PERF_REG_X86_R10) | \
+ (1ULL << PERF_REG_X86_R11) | \
+ (1ULL << PERF_REG_X86_R12) | \
+ (1ULL << PERF_REG_X86_R13) | \
+ (1ULL << PERF_REG_X86_R14) | \
+ (1ULL << PERF_REG_X86_R15))
+
int perf_reg_validate(u64 mask)
{
if (!mask || mask & REG_RESERVED)
return -EINVAL;

+ if (mask & REG_NOSUPPORT)
+ return -EINVAL;
+
return 0;
}