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

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Message-ID: <b5ee243c-5122-4476-8978-0454b54283d8@arm.com>
Date: Mon, 13 Jan 2025 16:49:04 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Ilkka Koskinen <ilkka@...amperecomputing.com>
Cc: 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 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.

Suzuki


> 
> Cheers, Ilkka