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b=u/OMXgWu+chO3gvSI12/PPBLGLAG6Xmt6zeic+C0lrMmuuBOFfaJ6NcDr3wEsVEVc EBqviFGr9mMYUGB9SRrwlDRUmyhf06XUyR8nhG95dPymq1tt/woI00vES7KjJgA4zd JhAPgv0JIj7NDVGlazIOCO5TSvA8lTlL1X8XNjI44EYzACpCeCk1d2DwUqW8VStSyI nvu1TAWAspCQtHJo7kjF5KHQBnkrAp41psY4G3AflGpg+hnQUCwvE7aFg0NlOyTUjJ mi/rXt8Z3sz0FkVowK9jcQX2aE7+euJiZyT170qfAwD1tXz/RQVkpf7HT+xUkYBXWE B7ca6w+Ds4q+A== Message-ID: Date: Mon, 23 Mar 2026 12:56:33 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: Fix soft-dirty kselftest supported check To: Audra Mitchell , akpm@linux-foundation.org Cc: ljs@kernel.org, Liam.Howlett@oracle.com, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, shuah@kernel.org, usama.anjum@collabora.com, colin.i.king@gmail.com, avagin@google.com, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260320184010.759461-1-audra@redhat.com> <20260320184010.759461-2-audra@redhat.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 41EB51C0007 X-Stat-Signature: cqai84kyb31oqgggf43r69bkex6so3z3 X-Rspam-User: X-HE-Tag: 1774266999-554354 X-HE-Meta: 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 KkJZ3YTk HTxuJp6IzqSOPH2TrFeN9+4+oWsTElup+pWJxUtYgBrBZbd/9uj4Xv+dK0LmXnAWmehQ+eD6WbQUI14QXhy1TqeBz/BODTJTli8G2kC5JQRQo+bkncix7CbtWmRBrp6TXv/a6u1WqXxM8njOoQBoPk3tRvlWL+DfyQG3lKttqRf8aGYjcK5kz1XGes1YjhmPZNKdPNiDHXOIXb9oWAd3AcEsQCRdRaBmt4b5+CRS/x4McJxV0c5u3beWW6P5yhxMtYM4j4Cl8VQPSQv9gd0tLFvkCGmAdDiPVJavO8OWS6qZ39ZK6g7e/i40hjbe04JmUQBtPAhhh3UMikOPYaCiS0F5BbgjdxtuMcEJX Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/20/26 19:39, Audra Mitchell wrote: > On architectures with separate user address space, such as s390 or > those without an MMU, the soft-dirty kselftest may fail when checking > to see if the feature is supported. > > # -------------------- > # running ./soft-dirty > # -------------------- > # TAP version 13 > # 1..15 > # Bail out! PAGEMAP_SCAN succeeded unexpectedly > # # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > # [FAIL] > not ok 1 soft-dirty # exit=1 > # SUMMARY: PASS=0 SKIP=0 FAIL=1 > > The soft-dirty test will initate an ioctl with the PAGEMAP_SCAN flag with > an invalid address for the page_region. This is done intentionally to > have the ioctl return with an expected EFAULT and with the correct > categories returned. > > However, on architectures with separate user address space, such as s390 or > those without an MMU, the call to __access_ok (used to validate the > variables provided with the ioctl) will always return true and we will not > fail as expected. > > if (IS_ENABLED(CONFIG_ALTERNATE_USER_ADDRESS_SPACE) || > !IS_ENABLED(CONFIG_MMU)) > return true; > > Let's simplify the check for PAGEMAP_SCAN and provide a valid page_region > address so that we get a non-errno return if it is supported. > > Fixes: 600bca580579 ("selftests/mm: check that PAGEMAP_SCAN returns correct categories") > > Signed-off-by: Audra Mitchell > --- > tools/testing/selftests/mm/vm_util.c | 24 +++++++++++++++--------- > 1 file changed, 15 insertions(+), 9 deletions(-) > > diff --git a/tools/testing/selftests/mm/vm_util.c b/tools/testing/selftests/mm/vm_util.c > index a6d4ff7dfdc0..82998406b335 100644 > --- a/tools/testing/selftests/mm/vm_util.c > +++ b/tools/testing/selftests/mm/vm_util.c > @@ -67,20 +67,26 @@ static uint64_t pagemap_scan_get_categories(int fd, char *start) > } > > /* `start` is any valid address. */ > -static bool pagemap_scan_supported(int fd, char *start) > +static bool pagemap_scan_supported(int fd) > { > + const size_t pagesize = getpagesize(); > static int supported = -1; > - int ret; > + struct page_region r; > + void *test_area; > > if (supported != -1) > return supported; > > - /* Provide an invalid address in order to trigger EFAULT. */ > - ret = __pagemap_scan_get_categories(fd, start, (struct page_region *) ~0UL); > - if (ret == 0) > - ksft_exit_fail_msg("PAGEMAP_SCAN succeeded unexpectedly\n"); > - > - supported = errno == EFAULT; > + test_area = mmap(0, pagesize, PROT_READ | PROT_WRITE, > + MAP_ANONYMOUS | MAP_PRIVATE, 0, 0); > + if (test_area == MAP_FAILED) { > + ksft_print_msg("WARN: mmap() failed: %s\n", strerror(errno)); > + supported = 0; > + } else { > + supported = __pagemap_scan_get_categories(fd, test_area, &r) >= 0; You have to cast it to a (long) first before comparing, like we do in pagemap_scan_get_categories(). Maybe best written as long ret = __pagemap_scan_get_categories(fd, test_area, &r); if (ret >= 0) supported = 1; > + ksft_print_msg("errno: %d\n", errno); I guess we should drop that, was mostly for testing. Thanks! -- Cheers, David