On 17/05/2023 07:55, Umesh Nerlige Ramappa wrote:
On Tue, May 16, 2023 at 05:25:50PM -0700, Dixit, Ashutosh wrote:
On Tue, 16 May 2023 16:35:28 -0700, Umesh Nerlige Ramappa wrote:
Hi Umesh/Tvrtko,
Mostly repeating comments/questions made on the previous patch below.
First of all thanks for improving this, my v1 obviously wasn't good enough.
From: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Having it as u64 was a confusing (but harmless) mistake.
Also add some asserts to make sure the internal field does not overflow
in the future.
v2: Fix WARN_ON firing for INTERRUPT event (Umesh)
Signed-off-by: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Signed-off-by: Umesh Nerlige Ramappa <umesh.nerlige.ramappa@xxxxxxxxx>
Cc: Ashutosh Dixit <ashutosh.dixit@xxxxxxxxx>
---
drivers/gpu/drm/i915/i915_pmu.c | 26 ++++++++++++++++++--------
1 file changed, 18 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/drm/i915/i915_pmu.c
b/drivers/gpu/drm/i915/i915_pmu.c
index 7ece883a7d95..96543dce2db1 100644
--- a/drivers/gpu/drm/i915/i915_pmu.c
+++ b/drivers/gpu/drm/i915/i915_pmu.c
@@ -50,7 +50,7 @@ static u8 engine_event_instance(struct perf_event
*event)
return (event->attr.config >> I915_PMU_SAMPLE_BITS) & 0xff;
}
-static bool is_engine_config(u64 config)
+static bool is_engine_config(const u64 config)
{
return config < __I915_PMU_OTHER(0);
}
@@ -88,9 +88,20 @@ static unsigned int config_bit(const u64 config)
return other_bit(config);
}
-static u64 config_mask(u64 config)
+static u32 config_mask(const u64 config)
{
- return BIT_ULL(config_bit(config));
+ unsigned int bit = config_bit(config);
Give that config_bit() can return -1 (I understand it is avoided in
moving
the code to config_mask from config_bit), maybe the code below should
also
have that check?
config_mask is only called to check frequency related events in the
code, so I don't see it returing -1 here.
Yeah that should be fine since -1 would make the below asserts fire
anyway. (If it would get called from a different path in the future.)
int bit = config_bit(config);
if (bit != -1)
{
...
}
Though as mentioned below the 'if (__builtin_constant_p())' would have to
go. Maybe the code could even have stayed in config_bit with the check.
+
+ if (__builtin_constant_p(config))
+ BUILD_BUG_ON(bit >
+ BITS_PER_TYPE(typeof_member(struct i915_pmu,
+ enable)) - 1);
Given that config comes from the event (it is event->attr.config), can
this
ever be a builtin constant?
Not sure about earlier code where these checks were inside config_bit(),
but with changes I made, I don't see this being a builtin constant.
However, nothing prevents a caller from just passing a builtin_constant
to this in future.
Are you sure? I would have thought it would always be a compile time
constant now that the check is in config_mask. Aahhh.. with the
multi-tile changes maybe it can't unroll the loops and calculate the
masks at compile time. Maybe it is a bit too much and we should drop the
__builtin_constant_p branch? Probably.. But I guess it is safe to use
GEM_WARN_ON_ONCE instead of WARN_ON_ONCE since there are no external
callers (nothing coming from event) now. That way at least production
builds don't have to have the check.
Regards,
Tvrtko
Thanks,
Umesh
+ else
+ WARN_ON_ONCE(bit >
+ BITS_PER_TYPE(typeof_member(struct i915_pmu,
+ enable)) - 1);
There is really an even stricter limit on what the bit can be, which
is the
total number of possible events but anyway this is good enough.
After addressing the above, this patch is:
Reviewed-by: Ashutosh Dixit <ashutosh.dixit@xxxxxxxxx>
+
+ return BIT(config_bit(config));
}
static bool is_engine_event(struct perf_event *event)
@@ -633,11 +644,10 @@ static void i915_pmu_enable(struct perf_event
*event)
{
struct drm_i915_private *i915 =
container_of(event->pmu, typeof(*i915), pmu.base);
+ const unsigned int bit = event_bit(event);
struct i915_pmu *pmu = &i915->pmu;
unsigned long flags;
- unsigned int bit;
- bit = event_bit(event);
if (bit == -1)
goto update;
@@ -651,7 +661,7 @@ static void i915_pmu_enable(struct perf_event
*event)
GEM_BUG_ON(bit >= ARRAY_SIZE(pmu->enable_count));
GEM_BUG_ON(pmu->enable_count[bit] == ~0);
- pmu->enable |= BIT_ULL(bit);
+ pmu->enable |= BIT(bit);
pmu->enable_count[bit]++;
/*
@@ -698,7 +708,7 @@ static void i915_pmu_disable(struct perf_event
*event)
{
struct drm_i915_private *i915 =
container_of(event->pmu, typeof(*i915), pmu.base);
- unsigned int bit = event_bit(event);
+ const unsigned int bit = event_bit(event);
struct i915_pmu *pmu = &i915->pmu;
unsigned long flags;
@@ -734,7 +744,7 @@ static void i915_pmu_disable(struct perf_event
*event)
* bitmask when the last listener on an event goes away.
*/
if (--pmu->enable_count[bit] == 0) {
- pmu->enable &= ~BIT_ULL(bit);
+ pmu->enable &= ~BIT(bit);
pmu->timer_enabled &= pmu_needs_timer(pmu, true);
}
--
2.36.1
