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

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Message-ID: <aTg2mKHKyq9ibFoU@gmail.com>
Date: Tue, 9 Dec 2025 22:47:52 +0800
From: Chunyu Hu <chuhu@...hat.com>
To: Luiz Capitulino <luizcap@...hat.com>
Cc: akpm@...ux-foundation.org, david@...nel.org, shuah@...nel.org,
	linux-mm@...ck.org, 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 Mon, Dec 08, 2025 at 10:47:19AM -0500, Luiz Capitulino wrote:
> 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.

Thank you for the review. Let me update a v2 to shorten this comment as
your suggested. And change the title to 'require 6 hugepages in
va_high_addr_switch hugetlb test.

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