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[54.240.197.234]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a30764e9e7sm17932475e9.2.2026.10.23.10.23.47 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 23 Oct 2026 10:23:48 -0700 (PDT) From: Fred Griffoul To: Ackerley Tng Cc: Alex Williamson , Alexander Graf , Alexander Viro , Alexey Kardashevskiy , Andrew Morton , "Aneesh Kumar K.V" , Ashish Kalra , Baolin Wang , Baolu Lu , Bill Wendling , Borislav Petkov , Catalin Marinas , Christian Brauner , =?utf-8?q?Christian_K=C3=B6nig?= , Connor Williamson , Dave Hansen , Dave Jiang , David Hildenbrand , David Rientjes , David Woodhouse , Erdem Aktas , Frank van der Linden , Gregory Price , "H. Peter Anvin" , Hugh Dickins , Ingo Molnar , Jacob Pan , James Houghton , Jan Kara , Jason Gunthorpe , Jianxiong Gao , Joerg Roedel , Joey Gouly , John Starks , Jonathan Corbet , Justin Stitt , Kevin Tian , Lorenzo Stoakes , Marc Zyngier , Michael Roth , Mike Rapoport , Nathan Chancellor , Nick Desaulniers , Nicolin Chen , Oliver Upton , Paolo Bonzini , Pratyush Yadav , Randy Dunlap , Robin Murphy , Samiullah Khawaja , Sean Christopherson , Shuah Khan , Steffen Eiden , Steven Price , Suzuki K Poulose , Tarun Sahu , Thomas Gleixner , Tom Lendacky , Tycho Andersen , Vishal Annapurve , Vlastimil Babka , Will Deacon , Xu Yilun , Yan Zhao , Zenghui Yu , x86@kernel.org, Shuah Khan , Fuad Tabba , kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, llvm@lists.linux.dev Subject: Re: [PATCH RFC v2 31/50] KVM: guest_memfd: Support getting PFNs for stage 2 from providers Date: Fri, 23 Oct 2026 17:23:47 +0000 Message-ID: <20261023172347.88443-1-griffoul@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20261022-gmem-alternative-providers-v2-31-5dd1dc6c660a@google.com> References: <20261022-gmem-alternative-providers-v2-0-5dd1dc6c660a@google.com> <20261022-gmem-alternative-providers-v2-31-5dd1dc6c660a@google.com> X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 441B180007 X-Stat-Signature: xyx68d7bedsxut8z71higg7hmzyxdt4i X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_GIT autolearn=no autolearn_force=no version=4.0.1 X-Rspam-User: X-HE-Tag: 1792776231-399519 X-HE-Meta: U2FsdGVkX187jPUX+NTWVhw3YTT0A0unUE+XvNQoJr6xCfF+6kBPJoMMd+XQIilynqXi1UiAdXj9dvmb5FUIKVUs+YWzTIFCf+qkqkHDKxnvtyDZ/IJnNGJ++SMm12ZRwtwZGufT5AWFgxi+DnBMACH/wBgDsHJyhdNDBdHqNKufMYuXcLQduLJPPhQ58j04Dl4qJ3kbIAAdrTX1yZLtYiQe26cYN4Cd1RfhrHQ7JrtNKZPV+fETJ12/e6BvGPXdb8r6ezfdrMr1STIXRLh1mE0ifRzEuGUV5bkxcmOCn4BKWoDdoFUtI6Ih/qR5/O9yCrsY1xn5ehbSdS/G7kJ8uVINFC2u1CJYUA/d2GeULZpGMjUX11Yd9RE2IABgPCIf05vguHZqiF2KA0Ma5r0JCi25wFPiPPguUdHjY7jScr/oBhxxOfBqfu99CGGpX7i1Ja4BzNjf65aalQqb4qC5VLOZ6+fPybSl622NXehgftM1xQ4NUgIPt6RclMwYgy0BXqnOkbgtS7gRcni7r55Sc1xKvdgMiCSSCEBUrKDmVshrNHr1RhTjeupnltd3bYrM8TPRyyKpqO/WBqTjzBuuoXDn8gdRaG6PQoC83BdxtMDblQa/Q8KW1Su17nd3qvxfkqyhEUFqS0AFzbCsbd2daBy8FuAHZS1KosHqPAFrO6pGkZebE98DRGwgWxLAVzt0tQuLq07PE/W2ytRilfi1P4YpJnUbNWvGYwIuE4/bctLJ34/UEI4Sb5RntPiNBKweRaF6NVLdP2O3UNqz1XLihLuQ4lVa0Vr4sFd71jZLKpxc0G1h6WPEwFYDA+RucC+YZiry7HCORjQ243wno1jzmYct6q80KZ0PQwHbp22nXt/67XprY7w2Qhx85X62soGkQRv0Y/YLmLgtKO8f9lJN/uvGKx0dv88K1MQivmYdXFj2fj7ZYNrGwOBW4pexPYs5JGnVSVs1gx+KyIyNcc3 7Zs/ewGk 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 > + int (*get_pfn)(void *provider, pgoff_t index, unsigned long *pfn, > + int *max_order); Should get_pfn() also return attributes of the frame? Only the provider knows them, and every mapping of the frame has to follow them. Two examples: - Read only. A provider may lend a page that the guest can read but not write. I know you dropped this from the sample to keep things simple, but without it guest_memfd maps every frame writable, and there is no other way to make a guest_memfd page read only. - Aliased. The frame is also reachable somewhere else, e.g. a ring shared with a device. Such a frame must not become private; see my reply to 34/50. A u32 of flags, with 0 for today's behaviour, would cover both and leave room for more later. Fred