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[87.161.170.17]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4507253bebdsm13854235e9.4.2025.05.28.03.45.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 28 May 2025 03:45:06 -0700 (PDT) Message-ID: <7cb7f23a-ce9e-4664-8083-deb73ed23da3@redhat.com> Date: Wed, 28 May 2025 12:44:59 +0200 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> From: David Hildenbrand 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: <232960c2-81db-47ca-a337-38c4bce5f997@arm.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: b2MUmdE0dO2E3Ngqn5SBPmJb7JnZA9HqUl-ak_OuqyE_1748429108 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 4D73BA000F X-Stat-Signature: qhj7z4txd1kdkwqiarbxoumurhze5pui X-Rspam-User: X-HE-Tag: 1748429111-749695 X-HE-Meta: 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 loxBa60I XA3yh7qYyukvmIJM9DR3kInO9CuRQ0LjRoyJfCZOG6JfF5KuZF0sWqFcp03RA48tmXSPqgWgXPUrdV38groZla7lqLmPkaATeBbeCnGtU7JJrqIPmd1fYWZOP9e6CGgoRfUsT X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: 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 think perhaps the only safe way to handle this is to parse /proc/iomem for a > region of "System RAM" that is at least 2 pages then use that for your read > tests. This would also solve the hypothetical issue of reading something that > has read size effects. That sounds also plausible yes. I somehow remembered that mmap() would fail if "there is nothing". > > I also spotted a few nits while reading the code... > >> >> On current x86-64 with PAT inside a VM, all tests pass: >> >> TAP version 13 >> 1..6 >> # Starting 6 tests from 1 test cases. >> # RUN pfnmap.madvise_disallowed ... >> # OK pfnmap.madvise_disallowed >> ok 1 pfnmap.madvise_disallowed >> # RUN pfnmap.munmap_split ... >> # OK pfnmap.munmap_split >> ok 2 pfnmap.munmap_split >> # RUN pfnmap.mremap_fixed ... >> # OK pfnmap.mremap_fixed >> ok 3 pfnmap.mremap_fixed >> # RUN pfnmap.mremap_shrink ... >> # OK pfnmap.mremap_shrink >> ok 4 pfnmap.mremap_shrink >> # RUN pfnmap.mremap_expand ... >> # OK pfnmap.mremap_expand >> ok 5 pfnmap.mremap_expand >> # RUN pfnmap.fork ... >> # OK pfnmap.fork >> ok 6 pfnmap.fork >> # PASSED: 6 / 6 tests passed. >> # Totals: pass:6 fail:0 xfail:0 xpass:0 skip:0 error:0 >> >> However, we are able to trigger: >> >> [ 27.888251] x86/PAT: pfnmap:1790 freeing invalid memtype [mem 0x00000000-0x00000fff] >> >> There are probably more things worth testing in the future, such as>> MAP_PRIVATE handling. But this set of tests is sufficient to cover most of >> the things we will rework regarding PAT handling. >> >> Cc: Andrew Morton >> Cc: Shuah Khan >> Cc: Lorenzo Stoakes >> Cc: Ingo Molnar >> Cc: Peter Xu >> Cc: Dev Jain >> Signed-off-by: David Hildenbrand >> --- >> >> Hopefully I didn't miss any review feedback. >> >> v1 -> v2: >> * Rewrite using kselftest_harness, which simplifies a lot of things >> * Add to .gitignore and run_vmtests.sh >> * Register signal handler on demand >> * Use volatile trick to force a read (not factoring out FORCE_READ just yet) >> * Drop mprotect() test case >> * Add some more comments why we test certain things >> * Use NULL for mmap() first parameter instead of 0 >> * Smaller fixes >> >> --- >> tools/testing/selftests/mm/.gitignore | 1 + >> tools/testing/selftests/mm/Makefile | 1 + >> tools/testing/selftests/mm/pfnmap.c | 196 ++++++++++++++++++++++ >> tools/testing/selftests/mm/run_vmtests.sh | 4 + >> 4 files changed, 202 insertions(+) >> create mode 100644 tools/testing/selftests/mm/pfnmap.c >> >> diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore >> index 91db34941a143..824266982aa36 100644 >> --- a/tools/testing/selftests/mm/.gitignore >> +++ b/tools/testing/selftests/mm/.gitignore >> @@ -20,6 +20,7 @@ mremap_test >> on-fault-limit >> transhuge-stress >> pagemap_ioctl >> +pfnmap >> *.tmp* >> protection_keys >> protection_keys_32 >> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile >> index ad4d6043a60f0..ae6f994d3add7 100644 >> --- a/tools/testing/selftests/mm/Makefile >> +++ b/tools/testing/selftests/mm/Makefile >> @@ -84,6 +84,7 @@ TEST_GEN_FILES += mremap_test >> TEST_GEN_FILES += mseal_test >> TEST_GEN_FILES += on-fault-limit >> TEST_GEN_FILES += pagemap_ioctl >> +TEST_GEN_FILES += pfnmap >> TEST_GEN_FILES += thuge-gen >> TEST_GEN_FILES += transhuge-stress >> TEST_GEN_FILES += uffd-stress >> diff --git a/tools/testing/selftests/mm/pfnmap.c b/tools/testing/selftests/mm/pfnmap.c >> new file mode 100644 >> index 0000000000000..8a9d19b6020c7 >> --- /dev/null >> +++ b/tools/testing/selftests/mm/pfnmap.c >> @@ -0,0 +1,196 @@ >> +// SPDX-License-Identifier: GPL-2.0-only >> +/* >> + * Basic VM_PFNMAP tests relying on mmap() of '/dev/mem' >> + * >> + * Copyright 2025, Red Hat, Inc. >> + * >> + * Author(s): David Hildenbrand >> + */ >> +#define _GNU_SOURCE >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +#include "../kselftest_harness.h" >> +#include "vm_util.h" >> + >> +static sigjmp_buf sigjmp_buf_env; >> + >> +static void signal_handler(int sig) >> +{ >> + siglongjmp(sigjmp_buf_env, -EFAULT); >> +} >> + >> +static int test_read_access(char *addr, size_t size, size_t pagesize) >> +{ >> + size_t offs; >> + int ret; >> + >> + if (signal(SIGSEGV, signal_handler) == SIG_ERR) >> + return -EINVAL; >> + >> + ret = sigsetjmp(sigjmp_buf_env, 1); >> + if (!ret) { >> + for (offs = 0; offs < size; offs += pagesize) >> + /* Force a read that the compiler cannot optimize out. */ >> + *((volatile char *)(addr + offs)); >> + } >> + if (signal(SIGSEGV, signal_handler) == SIG_ERR) > > I think you mean: > if (signal(SIGSEGV, SIG_DFL) == SIG_ERR) > > Otherwise your signal_handler will remain installed, right? Yeah, copy and past error. > >> + return -EINVAL; >> + >> + return ret; >> +} >> + >> +FIXTURE(pfnmap) >> +{ >> + size_t pagesize; >> + int dev_mem_fd; >> + char *addr1; >> + size_t size1; >> + char *addr2; >> + size_t size2; >> +}; >> + >> +FIXTURE_SETUP(pfnmap) >> +{ >> + self->pagesize = getpagesize(); >> + >> + 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); >> + if (self->addr1 == MAP_FAILED) >> + SKIP(return, "Cannot mmap '/dev/mem'\n"); >> + >> + /* ... and want to be able to read from them. */ >> + if (test_read_access(self->addr1, self->size1, self->pagesize)) >> + SKIP(return, "Cannot read-access mmap'ed '/dev/mem'\n"); >> + >> + self->size2 = 0; >> + self->addr2 = MAP_FAILED; > > Do you need to init all the params in FIXTURE(pfnmap) to their "safe" values > before any possible early returns? We don't want FIXTURE_TEARDOWN(pfnmap) > getting confused. If FIXTURE_SETUP fails, we'll exit immediately. See __TEST_F_IMPL(). Note that all tests are executed in a fork'ed child process, so quitting early (or not even having FIXTURE_TEARDOWN in most cases ...) does not really matter. -- Cheers, David / dhildenb