linux-kernel - Re: [PATCH v7 1/7] perf/amd/iommu: Misc fix up perf_iommu

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Date:   Wed, 11 Jan 2017 11:32:38 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
Cc:     linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        joro@...tes.org, peterz@...radead.org, mingo@...hat.com
Subject: Re: [PATCH v7 1/7] perf/amd/iommu: Misc fix up perf_iommu_read

On Mon, Jan 09, 2017 at 09:33:41PM -0600, Suravee Suthikulpanit wrote:
> This patch contains the following minor fixup:

For the future: never say "this patch" in the commit message - just
explain *why* the patch is needed.

>   * Fixed overflow handling since u64 delta would lose the MSB sign bit.

Past tense also reads funnily: "Fix overflow handling ..." sounds much
better.

>   * Remove unnecessary local64_set().

But you don't remove it - you add it. Huh?

>   * Coding style and make use of GENMASK_ULL macro.
> 
> Cc: Peter Zijlstra <peterz@...radead.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
> ---
>  arch/x86/events/amd/iommu.c | 25 +++++++++++++------------
>  1 file changed, 13 insertions(+), 12 deletions(-)
> 
> diff --git a/arch/x86/events/amd/iommu.c b/arch/x86/events/amd/iommu.c
> index b28200d..f387baf 100644
> --- a/arch/x86/events/amd/iommu.c
> +++ b/arch/x86/events/amd/iommu.c
> @@ -319,29 +319,30 @@ static void perf_iommu_start(struct perf_event *event, int flags)
>  
>  static void perf_iommu_read(struct perf_event *event)
>  {
> -	u64 count = 0ULL;
> -	u64 prev_raw_count = 0ULL;
> -	u64 delta = 0ULL;
> +	u64 cnt, prev;

"count" was fine.

> +	s64 delta;
>  	struct hw_perf_event *hwc = &event->hw;
>  	pr_debug("perf: amd_iommu:perf_iommu_read\n");

...

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.