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[80.230.48.7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-45d9ed2f738sm8558986f8f.16.2026.05.14.12.08.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 14 May 2026 12:08:19 -0700 (PDT) Date: Thu, 14 May 2026 15:08:13 -0400 From: "Michael S. Tsirkin" To: Gregory Price Cc: linux-kernel@vger.kernel.org, "David Hildenbrand (Arm)" , Jason Wang , Xuan Zhuo , Eugenio =?iso-8859-1?Q?P=E9rez?= , Muchun Song , Oscar Salvador , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Baolin Wang , Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Hugh Dickins , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Christoph Lameter , David Rientjes , Roman Gushchin , Harry Yoo , Axel Rasmussen , Yuanchu Xie , Wei Xu , Chris Li , Kairui Song , Kemeng Shi , Nhat Pham , Baoquan He , virtualization@lists.linux.dev, linux-mm@kvack.org, Andrea Arcangeli Subject: Re: [PATCH v7 09/31] mm: use folio_zero_user for user pages in post_alloc_hook Message-ID: <20260514150750-mutt-send-email-mst@kernel.org> References: <45d1ea85b574399459a64fdba28fcf04abfa3e7e.1778616612.git.mst@redhat.com> <20260514135214-mutt-send-email-mst@kernel.org> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: 7kj4R3Wus_ZORcldSpiiH5OHwJ_yFA0q4_JezU6Uptg_1778785701 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspam-User: X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 3EE6C40005 X-Stat-Signature: da335c6pw8o9n4wjsse57xhwsdyokpqi X-HE-Tag: 1778785704-943690 X-HE-Meta: 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 98ME3R3I 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Thu, May 14, 2026 at 02:56:54PM -0400, Gregory Price wrote: > On Thu, May 14, 2026 at 02:00:31PM -0400, Michael S. Tsirkin wrote: > > On Thu, May 14, 2026 at 09:49:33AM -0400, Gregory Price wrote: > > > > There are calls with no __GFP_ZERO but they do not allocate userspace pages. > > > > - drm_pagemap.c: GFP_HIGHUSER -- no zero. But this is a DRM device > > page migration, the page content is preserved from the source. > > > > - test_hmm.c: GFP_HIGHUSER_MOVABLE -- no zero. Test driver, pages get > > content from device. > > > > - mm/ksm.c: GFP_HIGHUSER_MOVABLE -- no zero. KSM merges identical > > pages, content comes from the source page (copy). > > > > - mm/memory.c new_folio = GFP_HIGHUSER_MOVABLE > > - no zero. This is CoW, content is copied from old page. > > > > - mm/userfaultfd.c: GFP_HIGHUSER_MOVABLE - no zero. Content comes from userspace via userfaultfd. > > > > - arm64/fault.c: __GFP_ZEROTAGS not __GFP_ZERO. MTE tag zeroing, not page zeroing. Page is zeroed separately. > > > > Right, so in all of these cases, it would be just as correct to pass > USER_ADDR_NONE I imagine :] Hmm. Are you sure? Isn't the address used for numa policy? > i.e. the user address is irrelevant, and the caller is responsible for > sanitization before return if it's relevant. > > Otherwise, passing (user_addr != -1) the buddy takes care of it for you. > > Just an obvious security bonus to all of this, but by no means a > requirement for your set. Just an observation. > > > > > I'd do this on top if possible. > > > > Yeah reasonable. > > ~Gregory