lkml.org 
[lkml]   [2022]   [Feb]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
SubjectRe: [PATCH v1 1/1] perf/smmuv3: Don't cast parameter in bit operations
From
On 2022-02-09 18:47, Andy Shevchenko wrote:
> While in this particular case it would not be a (critical) issue,
> the pattern itself is bad and error prone in case somebody blindly
> copies to their code.
>
> Don't cast parameter to unsigned long pointer in the bit operations.
> Instead copy to a local variable on stack of a proper type and use.

Seems reasonable, in fact in my build it appears to save a spill and
reload from the stack so the code actually gets a teeny bit better. Not
sure a cleanup warrants a "Fixes" tag, but either way,

Reviewed-by: Robin Murphy <robin.murphy@arm.com>

> Note, new compilers might warn on this line for potential outbound access.
>
> Fixes: 7d839b4b9e00 ("perf/smmuv3: Add arm64 smmuv3 pmu driver")
> Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
> ---
> drivers/perf/arm_smmuv3_pmu.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/perf/arm_smmuv3_pmu.c b/drivers/perf/arm_smmuv3_pmu.c
> index c49108a72865..00d4c45a8017 100644
> --- a/drivers/perf/arm_smmuv3_pmu.c
> +++ b/drivers/perf/arm_smmuv3_pmu.c
> @@ -654,6 +654,7 @@ static int smmu_pmu_offline_cpu(unsigned int cpu, struct hlist_node *node)
> static irqreturn_t smmu_pmu_handle_irq(int irq_num, void *data)
> {
> struct smmu_pmu *smmu_pmu = data;
> + DECLARE_BITMAP(ovs, BITS_PER_TYPE(u64));
> u64 ovsr;
> unsigned int idx;
>
> @@ -663,7 +664,8 @@ static irqreturn_t smmu_pmu_handle_irq(int irq_num, void *data)
>
> writeq(ovsr, smmu_pmu->reloc_base + SMMU_PMCG_OVSCLR0);
>
> - for_each_set_bit(idx, (unsigned long *)&ovsr, smmu_pmu->num_counters) {
> + bitmap_from_u64(ovs, ovsr);
> + for_each_set_bit(idx, ovs, smmu_pmu->num_counters) {
> struct perf_event *event = smmu_pmu->events[idx];
> struct hw_perf_event *hwc;
>

\
 
 \ /
  Last update: 2022-02-09 22:46    [W:0.046 / U:0.748 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site