linux-kernel - Re: [PATCH] coresight: catu: Fix number of pages while using 64k pages

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Message-ID: <3e8ea68a-b456-14df-eac1-e2932b3dbab0@os.amperecomputing.com>
Date: Mon, 13 Jan 2025 16:28:16 -0800 (PST)
From: Ilkka Koskinen <ilkka@...amperecomputing.com>
To: Suzuki K Poulose <suzuki.poulose@....com>
cc: Ilkka Koskinen <ilkka@...amperecomputing.com>, 
    Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>, 
    Alexander Shishkin <alexander.shishkin@...ux.intel.com>, 
    coresight@...ts.linaro.org, linux-arm-kernel@...ts.infradead.org, 
    linux-kernel@...r.kernel.org
Subject: Re: [PATCH] coresight: catu: Fix number of pages while using 64k
 pages



On Mon, 13 Jan 2025, Suzuki K Poulose wrote:
> On 10/01/2025 21:32, Ilkka Koskinen wrote:
>> 
>> Hi Suzuko,
>> 
>> On Fri, 10 Jan 2025, Suzuki K Poulose wrote:
>>> On 09/01/2025 21:53, Ilkka Koskinen wrote:
>>>> Trying to record a trace on kernel with 64k pages resulted in -ENOMEM.
>>>> This happens due to a bug in calculating the number of table pages, which
>>>> returns zero. Fix the issue by rounding up.
>>>> 
>>>> $ perf record --kcore -e cs_etm/@..._etr55,cycacc,branch_broadcast/k 
>>>> --per-thread taskset --cpu-list 1 dd if=/dev/zero of=/dev/null
>>>> failed to mmap with 12 (Cannot allocate memory)
>>>> 
>>> 
>>> Needs a Fixes tag.
>>> 
>>> Fixes : 8ed536b1e283 ("coresight: catu: Add support for scatter gather 
>>> tables")
>> 
>> That's a good point
>> 
>>> 
>>>> Signed-off-by: Ilkka Koskinen <ilkka@...amperecomputing.com>
>>>> ---
>>>>   drivers/hwtracing/coresight/coresight-catu.c | 2 +-
>>>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>>> 
>>>> diff --git a/drivers/hwtracing/coresight/coresight-catu.c b/drivers/ 
>>>> hwtracing/coresight/coresight-catu.c
>>>> index 275cc0d9f505..3378bb77e6b4 100644
>>>> --- a/drivers/hwtracing/coresight/coresight-catu.c
>>>> +++ b/drivers/hwtracing/coresight/coresight-catu.c
>>>> @@ -269,7 +269,7 @@ catu_init_sg_table(struct device *catu_dev, int node,
>>>>        * Each table can address upto 1MB and we can have
>>>>        * CATU_PAGES_PER_SYSPAGE tables in a system page.
>>>>        */
>>>> -    nr_tpages = DIV_ROUND_UP(size, SZ_1M) / CATU_PAGES_PER_SYSPAGE;
>>>> +    nr_tpages = DIV_ROUND_UP(size, CATU_PAGES_PER_SYSPAGE * SZ_1M);
>>>>       catu_table = tmc_alloc_sg_table(catu_dev, node, nr_tpages,
>>>>                       size >> PAGE_SHIFT, pages);
>>>>       if (IS_ERR(catu_table))
>>> 
>>> Looks good to me, I will queue this later for v6.15.
>>> 
>>> Suzuki
>> 
>> Sounds great. Just to confirm, are you ok to add the fixes line or would 
>> you prefer me to submit v2 with it?
>
> No, not required. I have picked this up for v6.15, and will push it out
> once v6.14-rc is out.

Perfect, thanks!

--Ilkka