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(p200300d82f26e700f1c5285b72a5d8c8.dip0.t-ipconnect.de. [2003:d8:2f26:e700:f1c5:285b:72a5:d8c8]) by smtp.gmail.com with ESMTPSA id a16-20020adffb90000000b0034af18ef68csm21643897wrr.5.2024.04.29.06.26.28 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 29 Apr 2024 06:26:28 -0700 (PDT) Message-ID: <2338119d-060b-4127-9199-5ff39fd62fc4@redhat.com> Date: Mon, 29 Apr 2024 15:26:22 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm/selftests: Don't prefault in gup_longterm tests To: Peter Xu Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christophe Leroy , Andrew Morton , "Aneesh Kumar K . V" , Lorenzo Stoakes , John Hubbard , linuxppc-dev@lists.ozlabs.org, Muchun Song , Jason Gunthorpe References: <20240428190151.201002-1-peterx@redhat.com> <20240428190151.201002-3-peterx@redhat.com> <4171dbb6-81c0-4553-a405-a55f75be4cb7@redhat.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: X-Mimecast-Spam-Score: 0 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: rspam08 X-Rspamd-Queue-Id: F109CA000F X-Stat-Signature: h77qt33h1ptxah66jebks8k1ogs96ynf X-Rspam-User: X-HE-Tag: 1714397192-769806 X-HE-Meta: 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 MRCaTPLe 8YK5CeYT2Jr29RaBF1RR28HkNb47EfTB9qTZTW22FNUXAH/Qh+Dug/riNF3X84EPNrH/CVE3MfYIpoDK7k6XXEfXDk+mhyky+kqlfCm1OVcgCILWQS8sKhomnawJ/03HCFZOl7Z/Swep0Y0bPGAHFivEn4SxXIrCbq54dIPqPB49hHuybrsRKRYXIRhosJhLTqNQeRkX2Qc2QTDURMMJJHrVPrUsGnr+hfmJU8Pgn+zdBXVMf7GdwxErWTcqkwLxkyBD0BhimumuuBEcCPCjiAFMqHSNXUTR1QpEhgoQh6bszzV5CwiX/siPH+VqQaZ+XlDmscXLndjJ4Lwv+NEDqUCFJBPcEwlojj4dOLsyJL/CyZOUCqcVU3dFbBKIMb0hk5M4xyBrz4rAJ6vzKJud9ozmh8XWRIbsfP9KbDisEGuLzNLynSNXV8Mrq2LicbiTLsNL4 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 29.04.24 15:10, Peter Xu wrote: > On Mon, Apr 29, 2024 at 09:28:15AM +0200, David Hildenbrand wrote: >> On 28.04.24 21:01, Peter Xu wrote: >>> Prefault, especially with RW, makes the GUP test too easy, and may not yet >>> reach the core of the test. >>> >>> For example, R/O longterm pins will just hit, pte_write()==true for >>> whatever cases, the unsharing logic won't be ever tested. >>> >>> This patch remove the prefault. This tortures more code paths at least to >>> cover the unshare care for R/O longterm pins, in which case the first R/O >>> GUP attempt will fault in the page R/O first, then the 2nd will go through >>> the unshare path, checking whether an unshare is needed. >>> >>> Cc: David Hildenbrand >>> Signed-off-by: Peter Xu >>> --- >>> tools/testing/selftests/mm/gup_longterm.c | 12 +++++++++--- >>> 1 file changed, 9 insertions(+), 3 deletions(-) >>> >>> diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c >>> index ad168d35b23b..488e32186246 100644 >>> --- a/tools/testing/selftests/mm/gup_longterm.c >>> +++ b/tools/testing/selftests/mm/gup_longterm.c >>> @@ -119,10 +119,16 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared) >>> } >>> /* >>> - * Fault in the page writable such that GUP-fast can eventually pin >>> - * it immediately. >>> + * Explicitly avoid pre-faulting in the page, this can help testing >>> + * more code paths. >>> + * >>> + * Take example of an upcoming R/O pin test, if we RW prefault the >>> + * page, such pin will directly skip R/O unsharing and the longterm >>> + * pin will success mostly always. When not prefaulted, R/O >>> + * longterm pin will first fault in a RO page, then the 2nd round >>> + * it'll go via the unshare check. Otherwise those paths aren't >>> + * covered. >>> */ >> This will mean that GUP-fast never succeeds, which removes quite some testing >> coverage for most other tests here. >> >> Note that the main motivation of this test was to test gup_fast_folio_allowed(), >> where we had issues with GUP-fast during development. > > Ah I didn't notice that, as I thought that whitelists memfd ones. > >> >> Would the following also get the job done? >> >> diff --git a/tools/testing/selftests/mm/gup_longterm.c b/tools/testing/selftests/mm/gup_longterm.c >> index ad168d35b23b7..e917a7c58d571 100644 >> --- a/tools/testing/selftests/mm/gup_longterm.c >> +++ b/tools/testing/selftests/mm/gup_longterm.c >> @@ -92,7 +92,7 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared) >> { >> __fsword_t fs_type = get_fs_type(fd); >> bool should_work; >> - char *mem; >> + char tmp, *mem; >> int ret; >> if (ftruncate(fd, size)) { >> @@ -119,10 +119,19 @@ static void do_test(int fd, size_t size, enum test_type type, bool shared) >> } >> /* >> - * Fault in the page writable such that GUP-fast can eventually pin >> - * it immediately. >> + * Fault in the page such that GUP-fast might be able to pin it >> + * immediately. To cover more cases, don't fault in pages writable when >> + * R/O pinning. >> */ >> - memset(mem, 0, size); >> + switch (type) { >> + case TEST_TYPE_RO: >> + case TEST_TYPE_RO_FAST: >> + tmp = *mem; >> + asm volatile("" : "+r" (tmp)); >> + break; >> + default: >> + memset(mem, 0, size); >> + }; >> switch (type) { >> case TEST_TYPE_RO: > > Yes this could work too. > > The test patch here doesn't need to rush. David, how about you prepare a > better and verified patch and post it separately, making sure to cover all > the things we used to cover plus the unshare? IIUC it used to be not > touched because of pte_write() always returns true with a write prefault. > > Then we let patch 1 go through first, and drop this one? Whatever you prefer! -- Cheers, David / dhildenb