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[2003:cb:c707:6e00:ff02:ec7a:ded5:ec1e]) by smtp.gmail.com with ESMTPSA id fj15-20020a05600c0c8f00b003cf894dbc4fsm1534778wmb.25.2023.01.05.00.16.44 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 05 Jan 2023 00:16:44 -0800 (PST) Message-ID: Date: Thu, 5 Jan 2023 09:16:43 +0100 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.6.0 Subject: Re: [PATCH 0/3] mm/uffd: Fix missing markers on hugetlb To: Peter Xu , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: Mike Kravetz , Muchun Song , Nadav Amit , Andrea Arcangeli , James Houghton , Axel Rasmussen , Andrew Morton References: <20230104225207.1066932-1-peterx@redhat.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230104225207.1066932-1-peterx@redhat.com> 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-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 87ED014000B X-Stat-Signature: c4rmygjqcqdbnurxxhd5eanm93x93nfa X-HE-Tag: 1672906608-145414 X-HE-Meta: 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 HYCFqZnv gKvou0tL03Vl3nYONz/BTsZGeashpDvF7Jz5JumIxbtBCRlgPACLBdIPDpqMukDSPezmtfVR0aQdn2kmLo3V+tS/d7jNBicx9DfqhfBEoc+0G/BeEzeNx47hCDcHfWcHog3ndrDujZmWPxusrlV28WQpzHgKFDAIM7IfIYlPThiwZAvATuaMN4PYwehZ5x60lt+ONk3Xf2wSzhk5/tAFfqfPgwQ== 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: On 04.01.23 23:52, Peter Xu wrote: > When James was developing the vma split fix for hugetlb pmd sharing, he > found that hugetlb uffd-wp is broken with the test case he developed [1]: > > https://lore.kernel.org/r/CADrL8HWSym93=yNpTUdWebOEzUOTR2ffbfUk04XdK6O+PNJNoA@mail.gmail.com > > Missing hugetlb pgtable pages caused uffd-wp to lose message when vma split > happens to be across a shared huge pmd range in the test. > > The issue is pgtable pre-allocation on hugetlb path was overlooked. That > was fixed in patch 1. Nice timing, I stumbled over that while adjusting background snapshot code in QEMU and wondered why we are not allocating page tables in that case -- and wanted to ask you why :) -- Thanks, David / dhildenb