[PATCH 0/2] arm: perf: Fix ARCH=arm build with GCC

[PATCH 0/2] arm: perf: Fix ARCH=arm build with GCC

[James Clark]

Two fixes for the broken build withh GCC currently in linux-next
(next-20231214)

James Clark (2):
  arm: perf: Fix ARCH=arm build with GCC in armv8pmu_write_evtype()
  arm: perf: Fix ARCH=arm build with GCC in armv8pmu_set_event_filter()

 drivers/perf/arm_pmuv3.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

-- 
2.34.1

[PATCH 1/2] arm: perf: Fix ARCH=arm build with GCC in armv8pmu_write_evtype()

[James Clark]

LLVM ignores everything inside the if statement and doesn't generate
errors, but GCC doesn't ignore it, resulting in the following error:

  drivers/perf/arm_pmuv3.c: In function ‘armv8pmu_write_evtype’:
  include/linux/bits.h:34:29: error: left shift count >= width of type [-Werror=shift-count-overflow]
  	34 |         (((~UL(0)) - (UL(1) << (l)) + 1) & \

Fix it by changing the if to #if.

Fixes: 3115ee021bfb ("arm64: perf: Include threshold control fields in PMEVTYPER mask")
Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Closes: https://lore.kernel.org/linux-arm-kernel/20231215120817.h2f3akgv72zhrtqo@pengutronix.de/
Signed-off-by: James Clark <james.clark@arm.com>
---
 drivers/perf/arm_pmuv3.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 23fa6c5da82c..3ed2086cefc3 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -631,8 +631,9 @@ static void armv8pmu_write_evtype(int idx, unsigned long val)
 			     ARMV8_PMU_EXCLUDE_EL0 |
 			     ARMV8_PMU_EXCLUDE_EL1;
 
-	if (IS_ENABLED(CONFIG_ARM64))
-		mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
+#if IS_ENABLED(CONFIG_ARM64)
+	mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
+#endif
 
 	val &= mask;
 	write_pmevtypern(counter, val);
-- 
2.34.1

[PATCH 2/2] arm: perf: Fix ARCH=arm build with GCC in armv8pmu_set_event_filter()

[James Clark]

LLVM ignores everything inside the if statement and doesn't generate
errors, but GCC does, resulting in the following:

  drivers/perf/arm_pmuv3.c: In function armv8pmu_set_event_filter:
  include/linux/bits.h:34:29: error: left shift count >= width of type [-Werror=shift-count-overflow]
  34 |         (((~UL(0)) - (UL(1) << (l)) + 1) & \

Fix it by changing the if to #if. This results in an unused function
warning for armv8pmu_event_threshold_control(), so suppress that too.

Fixes: 816c26754447 ("arm64: perf: Add support for event counting threshold")
Signed-off-by: James Clark <james.clark@arm.com>
---
 drivers/perf/arm_pmuv3.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
index 3ed2086cefc3..8aa23878019a 100644
--- a/drivers/perf/arm_pmuv3.c
+++ b/drivers/perf/arm_pmuv3.c
@@ -338,7 +338,7 @@ static bool armv8pmu_event_want_user_access(struct perf_event *event)
 	return ATTR_CFG_GET_FLD(&event->attr, rdpmc);
 }
 
-static u8 armv8pmu_event_threshold_control(struct perf_event_attr *attr)
+static __maybe_unused u8 armv8pmu_event_threshold_control(struct perf_event_attr *attr)
 {
 	u8 th_compare = ATTR_CFG_GET_FLD(attr, threshold_compare);
 	u8 th_count = ATTR_CFG_GET_FLD(attr, threshold_count);
@@ -1040,11 +1040,13 @@ static int armv8pmu_set_event_filter(struct hw_perf_event *event,
 		return -EINVAL;
 	}
 
-	if (IS_ENABLED(CONFIG_ARM64) && th) {
+#if IS_ENABLED(CONFIG_ARM64)
+	if (th) {
 		config_base |= FIELD_PREP(ARMV8_PMU_EVTYPE_TH, th);
 		config_base |= FIELD_PREP(ARMV8_PMU_EVTYPE_TC,
 					  armv8pmu_event_threshold_control(attr));
 	}
+#endif
 
 	/*
 	 * Install the filter into config_base as this is used to
-- 
2.34.1

Re: [PATCH 1/2] arm: perf: Fix ARCH=arm build with GCC in armv8pmu_write_evtype()

[Uwe Kleine-König]

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Hello,

On Fri, Dec 15, 2023 at 03:00:38PM +0000, James Clark wrote:
> diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
> index 23fa6c5da82c..3ed2086cefc3 100644
> --- a/drivers/perf/arm_pmuv3.c
> +++ b/drivers/perf/arm_pmuv3.c
> @@ -631,8 +631,9 @@ static void armv8pmu_write_evtype(int idx, unsigned long val)
>  			     ARMV8_PMU_EXCLUDE_EL0 |
>  			     ARMV8_PMU_EXCLUDE_EL1;
>  
> -	if (IS_ENABLED(CONFIG_ARM64))
> -		mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
> +#if IS_ENABLED(CONFIG_ARM64)
> +	mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
> +#endif

maybe add a comment about why you used an #if here, to prevent the
people sending patches that revert your change?

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH 1/2] arm: perf: Fix ARCH=arm build with GCC in armv8pmu_write_evtype()

[Mark Rutland]

On Fri, Dec 15, 2023 at 03:00:38PM +0000, James Clark wrote:
> LLVM ignores everything inside the if statement and doesn't generate
> errors, but GCC doesn't ignore it, resulting in the following error:
> 
>   drivers/perf/arm_pmuv3.c: In function 'armv8pmu_write_evtype':
>   include/linux/bits.h:34:29: error: left shift count >= width of type [-Werror=shift-count-overflow]
>   	34 |         (((~UL(0)) - (UL(1) << (l)) + 1) & \
> 
> Fix it by changing the if to #if.

I reckon it'd be cleaner to use GENMASK_ULL for the TH and TC fields, in
include/linux/perf/arm_pmu.h have:

| /*
|  * PMXEVTYPER: Event selection reg
|  */
| #define ARMV8_PMU_EVTYPE_EVENT GENMASK(15, 0)          /* Mask for EVENT bits */
| #define ARMV8_PMU_EVTYPE_TH    GENMASK_ULL(43, 32)     /* arm64 only */
| #define ARMV8_PMU_EVTYPE_TC    GENMASK_ULL(63, 61)     /* arm64 only */

IIUC that should silence this warning, and it'd remove the need for the
ifdeffery and other changes in patch 2.

Does that work, or am I missing something?

Thanks,
Mark.

> 
> Fixes: 3115ee021bfb ("arm64: perf: Include threshold control fields in PMEVTYPER mask")
> Reported-by: Uwe Kleine-K"onig <u.kleine-koenig@pengutronix.de>
> Closes: https://lore.kernel.org/linux-arm-kernel/20231215120817.h2f3akgv72zhrtqo@pengutronix.de/
> Signed-off-by: James Clark <james.clark@arm.com>
> ---
>  drivers/perf/arm_pmuv3.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
> index 23fa6c5da82c..3ed2086cefc3 100644
> --- a/drivers/perf/arm_pmuv3.c
> +++ b/drivers/perf/arm_pmuv3.c
> @@ -631,8 +631,9 @@ static void armv8pmu_write_evtype(int idx, unsigned long val)
>  			     ARMV8_PMU_EXCLUDE_EL0 |
>  			     ARMV8_PMU_EXCLUDE_EL1;
>  
> -	if (IS_ENABLED(CONFIG_ARM64))
> -		mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
> +#if IS_ENABLED(CONFIG_ARM64)
> +	mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
> +#endif
>  
>  	val &= mask;
>  	write_pmevtypern(counter, val);
> -- 
> 2.34.1
> 

Re: [PATCH 1/2] arm: perf: Fix ARCH=arm build with GCC in armv8pmu_write_evtype()

[James Clark]

On 15/12/2023 16:21, Mark Rutland wrote:
> On Fri, Dec 15, 2023 at 03:00:38PM +0000, James Clark wrote:
>> LLVM ignores everything inside the if statement and doesn't generate
>> errors, but GCC doesn't ignore it, resulting in the following error:
>>
>>   drivers/perf/arm_pmuv3.c: In function 'armv8pmu_write_evtype':
>>   include/linux/bits.h:34:29: error: left shift count >= width of type [-Werror=shift-count-overflow]
>>   	34 |         (((~UL(0)) - (UL(1) << (l)) + 1) & \
>>
>> Fix it by changing the if to #if.
> 
> I reckon it'd be cleaner to use GENMASK_ULL for the TH and TC fields, in
> include/linux/perf/arm_pmu.h have:
> 
> | /*
> |  * PMXEVTYPER: Event selection reg
> |  */
> | #define ARMV8_PMU_EVTYPE_EVENT GENMASK(15, 0)          /* Mask for EVENT bits */
> | #define ARMV8_PMU_EVTYPE_TH    GENMASK_ULL(43, 32)     /* arm64 only */
> | #define ARMV8_PMU_EVTYPE_TC    GENMASK_ULL(63, 61)     /* arm64 only */
> 
> IIUC that should silence this warning, and it'd remove the need for the
> ifdeffery and other changes in patch 2.
> 
> Does that work, or am I missing something?
> 
> Thanks,
> Mark.
> 

You're right that does work. For some reason I thought there was some
component of writing it to the mask that was the issue as well.

I'll send another version with that fix instead.

Thanks
James

>>
>> Fixes: 3115ee021bfb ("arm64: perf: Include threshold control fields in PMEVTYPER mask")
>> Reported-by: Uwe Kleine-K"onig <u.kleine-koenig@pengutronix.de>
>> Closes: https://lore.kernel.org/linux-arm-kernel/20231215120817.h2f3akgv72zhrtqo@pengutronix.de/
>> Signed-off-by: James Clark <james.clark@arm.com>
>> ---
>>  drivers/perf/arm_pmuv3.c | 5 +++--
>>  1 file changed, 3 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/perf/arm_pmuv3.c b/drivers/perf/arm_pmuv3.c
>> index 23fa6c5da82c..3ed2086cefc3 100644
>> --- a/drivers/perf/arm_pmuv3.c
>> +++ b/drivers/perf/arm_pmuv3.c
>> @@ -631,8 +631,9 @@ static void armv8pmu_write_evtype(int idx, unsigned long val)
>>  			     ARMV8_PMU_EXCLUDE_EL0 |
>>  			     ARMV8_PMU_EXCLUDE_EL1;
>>  
>> -	if (IS_ENABLED(CONFIG_ARM64))
>> -		mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
>> +#if IS_ENABLED(CONFIG_ARM64)
>> +	mask |= ARMV8_PMU_EVTYPE_TC | ARMV8_PMU_EVTYPE_TH;
>> +#endif
>>  
>>  	val &= mask;
>>  	write_pmevtypern(counter, val);
>> -- 
>> 2.34.1
>>