[PATCH 4/4] hwmon: (dell-smm) Measure time duration of SMM call around inlined asm

Pali Rohár
2018-01-27T16:24:16Z

Measure only inlined asm code, not other functions to have as precise as
possible measured time.

Signed-off-by: Pali Rohár <pali.rohar@gmail.com>
---
drivers/hwmon/dell-smm-hwmon.c | 14 ++++++++++----
1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c
index bf3bb7e1adab..e001afd53f46 100644
--- a/drivers/hwmon/dell-smm-hwmon.c
+++ b/drivers/hwmon/dell-smm-hwmon.c
@@ -147,14 +147,16 @@ static int i8k_smm_func(void *par)
int ebx = regs->ebx;
unsigned long duration;
ktime_t calltime, delta, rettime;
-
- calltime = ktime_get();
#endif

/* SMM requires CPU 0 */
if (smp_processor_id() != 0)
return -EBUSY;

+#ifdef DEBUG
+ calltime = ktime_get();
+#endif
+
#if defined(CONFIG_X86_64)
asm volatile("pushq %%rax\n\t"
"movl 0(%%rax),%%edx\n\t"
@@ -208,13 +210,17 @@ static int i8k_smm_func(void *par)
: "a"(regs)
: "%ebx", "%ecx", "%edx", "%esi", "%edi", "memory");
#endif
- if (rc != 0 || (regs->eax & 0xffff) == 0xffff || regs->eax == eax)
- rc = -EINVAL;

#ifdef DEBUG
rettime = ktime_get();
delta = ktime_sub(rettime, calltime);
duration = ktime_to_ns(delta) >> 10;
+#endif
+
+ if (rc != 0 || (regs->eax & 0xffff) == 0xffff || regs->eax == eax)
+ rc = -EINVAL;
+
+#ifdef DEBUG
pr_debug("smm(0x%.4x 0x%.4x) = 0x%.4x (took %7lu usecs)\n", eax, ebx,
(rc ? 0xffff : regs->eax & 0xffff), duration);
#endif
--
2.11.0