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[2003:d8:2f30:ec00:8f7e:58a4:ebf0:6a36]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a4eac8ad8csm1401860f8f.55.2025.05.28.05.40.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 May 2025 05:40:28 -0700 (PDT) Message-ID: <2de2bbdb-f719-4faf-822c-d855f1eb653a@redhat.com> Date: Wed, 28 May 2025 14:40:27 +0200 Precedence: bulk X-Mailing-List: linux-kselftest@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] selftests/mm: add simple VM_PFNMAP tests based on mmap'ing /dev/mem To: Ryan Roberts , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Andrew Morton , Shuah Khan , Lorenzo Stoakes , Ingo Molnar , Peter Xu , Dev Jain , Aishwarya TCV References: <20250509153033.952746-1-david@redhat.com> <232960c2-81db-47ca-a337-38c4bce5f997@arm.com> <7cb7f23a-ce9e-4664-8083-deb73ed23da3@redhat.com> <3c15a093-7c19-4c2a-a571-56a5ed4b445f@redhat.com> From: David Hildenbrand Content-Language: en-US Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28.05.25 12:53, Ryan Roberts wrote: > On 28/05/2025 11:48, David Hildenbrand wrote: >> On 28.05.25 12:44, David Hildenbrand wrote: >>> On 28.05.25 12:34, Ryan Roberts wrote: >>>> Hi David, >>>> >>>> >>>> On 09/05/2025 16:30, David Hildenbrand wrote: >>>>> Let's test some basic functionality using /dev/mem. These tests will >>>>> implicitly cover some PAT (Page Attribute Handling) handling on x86. >>>>> >>>>> These tests will only run when /dev/mem access to the first two pages >>>>> in physical address space is possible and allowed; otherwise, the tests >>>>> are skipped. >>>> >>>> We are seeing really horrible RAS errors with this test when run on arm64 tx2 >>>> machine. Based solely on reviewing the code, I think the problem is that tx2 >>>> doesn't have anything at phys address 0, so test_read_access() is trying to put >>>> trasactions out to a bad address on the bus. >>>> >>>> tx2 /proc/iomem: >>>> >>>> $ sudo cat /proc/iomem >>>> 30000000-37ffffff : PCI ECAM >>>> 38000000-3fffffff : PCI ECAM >>>> 40000000-5fffffff : PCI Bus 0000:00 >>>> ... >>>> >>>> Whereas my x86 box has some reserved memory: >>>> >>>> $ sudo cat /proc/iomem >>>> 00000000-00000fff : Reserved >>>> 00001000-0003dfff : System RAM >>>> ... >>>> >>> >>> A quick fix would be to make this test specific to x86 (the only one I >>> tested on). We should always have the lower two pages IIRC (BIOS stuff etc). > > I'm not sure how far along this patch is? I'm guessing mm-stable? Perhaps you > can do the quick fix, then I'd be happy to make this more robust for arm64 later? Can you give the following a quick test on that machine? Then, I can send it as a proper patch later. From 40fea063f2fcf1474fb47cb9aebdb04fd825032b Mon Sep 17 00:00:00 2001 From: David Hildenbrand Date: Wed, 28 May 2025 14:35:23 +0200 Subject: [PATCH] selftests/mm: two fixes for the pfnmap test When unregistering the signal handler, we have to pass SIG_DFL, and blindly reading from PFN 0 and PFN 1 seems to be problematic on !x86 systems. In particularly, on arm64 tx2 machines where noting resides at these physical memory locations, we can generate RAS errors. Let's fix it by scanning /proc/iomem for actual "System RAM". Reported-by: Ryan Roberts Closes: https://lore.kernel.org/all/232960c2-81db-47ca-a337-38c4bce5f997@arm.com/T/#u Fixes: 2616b370323a ("selftests/mm: add simple VM_PFNMAP tests based on mmap'ing /dev/mem") Signed-off-by: David Hildenbrand --- tools/testing/selftests/mm/pfnmap.c | 61 +++++++++++++++++++++++++++-- 1 file changed, 57 insertions(+), 4 deletions(-) diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c index 8a9d19b6020c7..4943927a7d1ea 100644 --- a/tools/testing/selftests/mm/pfnmap.c +++ b/tools/testing/selftests/mm/pfnmap.c @@ -12,6 +12,8 @@ #include #include #include +#include +#include #include #include #include @@ -43,14 +45,62 @@ static int test_read_access(char *addr, size_t size, size_t pagesize) /* Force a read that the compiler cannot optimize out. */ *((volatile char *)(addr + offs)); } - if (signal(SIGSEGV, signal_handler) == SIG_ERR) + if (signal(SIGSEGV, SIG_DFL) == SIG_ERR) return -EINVAL; return ret; } +static int find_ram_target(off_t *phys_addr, + unsigned long pagesize) +{ + unsigned long long start, end; + char line[80], *end_ptr; + FILE *file; + + /* Search /proc/iomem for the first suitable "System RAM" range. */ + file = fopen("/proc/iomem", "r"); + if (!file) + return -errno; + + while (fgets(line, sizeof(line), file)) { + /* Ignore any child nodes. */ + if (!isalnum(line[0])) + continue; + + if (!strstr(line, "System RAM\n")) + continue; + + start = strtoull(line, &end_ptr, 16); + /* Skip over the "-" */ + end_ptr++; + /* Make end "exclusive". */ + end = strtoull(end_ptr, NULL, 16) + 1; + + /* Actual addresses are not exported */ + if (!start && !end) + break; + + /* We need full pages. */ + start = (start + pagesize - 1) & ~(pagesize - 1); + end &= ~(pagesize - 1); + + if (start != (off_t)start) + break; + + /* We need two pages. */ + if (end > start + 2 * pagesize) { + fclose(file); + *phys_addr = start; + return 0; + } + } + return -ENOENT; +} + FIXTURE(pfnmap) { + off_t phys_addr; size_t pagesize; int dev_mem_fd; char *addr1; @@ -63,14 +113,17 @@ FIXTURE_SETUP(pfnmap) { self->pagesize = getpagesize(); + /* We'll require two physical pages throughout our tests ... */ + if (find_ram_target(&self->phys_addr, self->pagesize)) + SKIP(return, "Cannot find ram target in '/dev/iomem'\n"); + self->dev_mem_fd = open("/dev/mem", O_RDONLY); if (self->dev_mem_fd < 0) SKIP(return, "Cannot open '/dev/mem'\n"); - /* We'll require the first two pages throughout our tests ... */ self->size1 = self->pagesize * 2; self->addr1 = mmap(NULL, self->size1, PROT_READ, MAP_SHARED, - self->dev_mem_fd, 0); + self->dev_mem_fd, self->phys_addr); if (self->addr1 == MAP_FAILED) SKIP(return, "Cannot mmap '/dev/mem'\n"); @@ -129,7 +182,7 @@ TEST_F(pfnmap, munmap_split) */ self->size2 = self->pagesize; self->addr2 = mmap(NULL, self->pagesize, PROT_READ, MAP_SHARED, - self->dev_mem_fd, 0); + self->dev_mem_fd, self->phys_addr); ASSERT_NE(self->addr2, MAP_FAILED); } -- 2.49.0 -- Cheers, David / dhildenb