linux-kernel - Re: [PATCH v1 2/3] selftests/mm: allocate 6 hugepages in va_high_addr

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Message-ID: <efdd610d-a56f-4f3f-ab5c-9b0da1762ab6@redhat.com>
Date: Mon, 8 Dec 2025 10:47:19 -0500
From: Luiz Capitulino <luizcap@...hat.com>
To: Chunyu Hu <chuhu@...hat.com>, akpm@...ux-foundation.org,
 david@...nel.org, shuah@...nel.org, linux-mm@...ck.org
Cc: linux-kselftest@...r.kernel.org, linux-kernel@...r.kernel.org,
 lorenzo.stoakes@...cle.com, Liam.Howlett@...cle.com, vbabka@...e.cz,
 rppt@...nel.org, surenb@...gle.com, mhocko@...e.com
Subject: Re: [PATCH v1 2/3] selftests/mm: allocate 6 hugepages in
 va_high_addr_switch.sh

On 2025-12-07 07:22, Chunyu Hu wrote:
> The va_high_addr_switch test requires 6 hugepages, not 5. If running the
> test directly by: ./va_high_addr_switch.sh, the test will hit a mmap 'FAIL'
> caused by not enough hugepages:
>    ```
>    mmap(addr_switch_hint - hugepagesize, 2*hugepagesize, MAP_HUGETLB): 0x7f330f800000 - OK
>    mmap(addr_switch_hint , 2*hugepagesize, MAP_FIXED | MAP_HUGETLB): 0xffffffffffffffff - FAILED
>    ```
> The failure can't be hit if run the tests by running 'run_vmtests.sh -t
> hugevm' because the nr_hugepages is set to 128 at the beginning of
> run_vmtests.sh and va_high_addr_switch.sh skip the setup of nr_hugepages
> because already enough.
> 
> CC: Luiz Capitulino <luizcap@...hat.com>
> Fixes: d9d957bd7b61 ("selftests/mm: alloc hugepages in va_high_addr_switch test")
> Signed-off-by: Chunyu Hu <chuhu@...hat.com>
> ---
>   tools/testing/selftests/mm/va_high_addr_switch.sh | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/testing/selftests/mm/va_high_addr_switch.sh b/tools/testing/selftests/mm/va_high_addr_switch.sh
> index f89fe078a8e6..98f3dfab62c5 100755
> --- a/tools/testing/selftests/mm/va_high_addr_switch.sh
> +++ b/tools/testing/selftests/mm/va_high_addr_switch.sh
> @@ -111,8 +111,10 @@ setup_nr_hugepages()
>   
>   check_test_requirements
>   save_nr_hugepages
> -# 4 keep_mapped pages, and one for tmp usage
> -setup_nr_hugepages 5
> +# 5 keep_mapped hugepages are reserved in the first testings, and the last test
> +# requires two hugepages, with one verlaped with the last second test, so one
> +# extra, totally 6 hugepages

IMHO, I'd just say "The HugeTLB tests require 6 pages", otherwise the
fix look good to me.

> +setup_nr_hugepages 6
>   ./va_high_addr_switch --run-hugetlb
>   retcode=$?
>   restore_nr_hugepages