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

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Message-ID: <7fa2c7c2-0bbf-4d45-bc90-71c4a4a82c0c@arm.com>
Date: Fri, 10 Jan 2025 10:44:35 +0000
From: Suzuki K Poulose <suzuki.poulose@....com>
To: Ilkka Koskinen <ilkka@...amperecomputing.com>,
 Mike Leach <mike.leach@...aro.org>, James Clark <james.clark@...aro.org>,
 Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: 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 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")

> 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