linux-kernel - Re: [PATCH v2 1/1] selftests/mm: skip soft-dirty tests when CONFIG_MEM_SOFT

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Message-ID: <ada1b1f9-bd2b-4164-ae8c-80264d4f6dc0@redhat.com>
Date: Wed, 17 Sep 2025 15:08:41 +0200
From: David Hildenbrand <david@...hat.com>
To: Lance Yang <lance.yang@...ux.dev>, akpm@...ux-foundation.org,
 lorenzo.stoakes@...cle.com
Cc: shuah@...nel.org, ioworker0@...il.com, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH v2 1/1] selftests/mm: skip soft-dirty tests when
 CONFIG_MEM_SOFT_DIRTY is disabled

On 17.09.25 14:27, Lance Yang wrote:
> From: Lance Yang <lance.yang@...ux.dev>
> 
> The madv_populate and soft-dirty kselftests currently fail on systems where
> CONFIG_MEM_SOFT_DIRTY is disabled.
> 
> Introduce a new helper softdirty_supported() into vm_util.c/h to ensure
> tests are properly skipped when the feature is not enabled.
> 
> Signed-off-by: Lance Yang <lance.yang@...ux.dev>
> ---

[...]

> diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c
> index 56e9bd541edd..ac41d10454a5 100644
> --- a/tools/testing/selftests/mm/vm_util.c
> +++ b/tools/testing/selftests/mm/vm_util.c
> @@ -449,6 +449,25 @@ bool check_vmflag_pfnmap(void *addr)
>   	return check_vmflag(addr, "pf");
>   }
>   
> +bool softdirty_supported(void)
> +{
> +	char *addr;
> +	bool supported = false;
> +	const size_t pagesize = getpagesize();
> +
> +	/* New mappings are expected to be marked with VM_SOFTDIRTY (sd). */
> +	addr = mmap(0, pagesize, PROT_READ | PROT_WRITE,
> +		    MAP_ANONYMOUS | MAP_PRIVATE, 0, 0);
> +	if (!addr)
> +		ksft_exit_fail_msg("mmap failed\n");
> +
> +	if (check_vmflag(addr, "sd"))
> +		supported = true;

Reading the code again, this could just be

supported = check_vmflag(addr, "sd");


LGTM

Acked-by: David Hildenbrand <david@...hat.com>

-- 
Cheers

David / dhildenb