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[2003:d8:2f15:c300:d2ce:1fb5:2460:179a]) by smtp.gmail.com with ESMTPSA id a5-20020adffb85000000b0021e45afa7b0sm12800466wrr.109.2022.08.09.01.15.50 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 09 Aug 2022 01:15:50 -0700 (PDT) Message-ID: <6504c796-513a-3785-22a8-a933de37bf96@redhat.com> Date: Tue, 9 Aug 2022 10:15:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH] mm: re-allow pinning of zero pfns (again) Content-Language: en-US To: Alex Williamson , alex.sierra@amd.com, akpm@linux-foundation.org Cc: hch@lst.de, Felix.Kuehling@amd.com, apopple@nvidia.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <166002010021.381133.11357879752637949308.stgit@omen> From: David Hildenbrand Organization: Red Hat In-Reply-To: <166002010021.381133.11357879752637949308.stgit@omen> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09.08.22 06:42, Alex Williamson wrote: > The below referenced commit makes the same error as 1c563432588d ("mm: fix > is_pinnable_page against a cma page"), re-interpreting the logic to exclude > pinning of the zero page, which breaks device assignment with vfio. > > Link: https://lore.kernel.org/all/165490039431.944052.12458624139225785964.stgit@omen > Fixes: f25cbb7a95a2 ("mm: add zone device coherent type memory support") > Signed-off-by: Alex Williamson > --- > include/linux/mm.h | 5 ++--- > 1 file changed, 2 insertions(+), 3 deletions(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index 18e01474cf6b..772279ed7010 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -1544,9 +1544,8 @@ static inline bool is_longterm_pinnable_page(struct page *page) > if (mt == MIGRATE_CMA || mt == MIGRATE_ISOLATE) > return false; > #endif > - return !(is_device_coherent_page(page) || > - is_zone_movable_page(page) || > - is_zero_pfn(page_to_pfn(page))); > + return !(is_device_coherent_page(page) || is_zone_movable_page(page)) || > + is_zero_pfn(page_to_pfn(page)); > } > #else > static inline bool is_longterm_pinnable_page(struct page *page) :/ I guess the code was moved just at the time the old code was still in place, and when rebasing, the diff in the code was ignored. Reviewed-by: David Hildenbrand I have patches in the works that will properly break COW here to get anon pages instead of pinning the shared zeropage, which is questionable in COW mappings. -- Thanks, David / dhildenb