From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 7D3C0CA9EC5 for ; Mon, 12 Oct 2026 15:48:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3D5196B0088; Mon, 12 Oct 2026 11:48:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 385DE6B008A; Mon, 12 Oct 2026 11:48:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 275766B008C; Mon, 12 Oct 2026 11:48:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0017.hostedemail.com [216.40.44.17]) by kanga.kvack.org (Postfix) with ESMTP id E3D9D6B0088 for ; Mon, 12 Oct 2026 11:48:56 -0400 (EDT) Received: from smtpin30.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 73DF41610C5 for ; Mon, 12 Oct 2026 15:48:56 +0000 (UTC) X-FDA: 85314407472.30.615E6D8 Received: from mail-wm1-f46.google.com (mail-wm1-f46.google.com [209.85.128.46]) by imf16.hostedemail.com (Postfix) with ESMTP id 92C5D18000A for ; Mon, 12 Oct 2026 15:48:54 +0000 (UTC) Authentication-Results: imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=LtYFx8Hd; spf=pass (imf16.hostedemail.com: domain of griffoul@gmail.com designates 209.85.128.46 as permitted sender) smtp.mailfrom=griffoul@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1791820134; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=bz+XxQbQvV9Rkz3jiplflbfyEnwSo6hWkWyEVkUNcs8=; b=5yDI/JeDcZRv9BBs5pLijLpnaqhTIExCTiFtZJi0MB5wExlPILrET2mprk6W+1HSQaZHaW Dyyhj07gLmhiWytEPCrBbrr45PhJVBi6sSJv250BhxIDZqchv49zAuWlknADYQrhdA6zGn 0MAPjiJbeZRsq6mG05AqFhGU2fIqMWo= ARC-Authentication-Results: i=1; imf16.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=LtYFx8Hd; spf=pass (imf16.hostedemail.com: domain of griffoul@gmail.com designates 209.85.128.46 as permitted sender) smtp.mailfrom=griffoul@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1791820134; b=kDp2JO6YC9d0oH/Yazr+F7Q61kF2mT/PzCAbGwmcDHRJnZpJzCBlztT6MlOw9bvy/rimhw SJ1zMCXUDl4pSw9cw1tRE/CNNVJZ3pYmzYThsF5P7uRCQKpHS2GSZVbVaitGSUGxJ/L+CF pOJ5DBK4JZvRSofnYi4uHLD92v7+yh0= Received: by mail-wm1-f46.google.com with SMTP id 5b1f17b1804b1-4a17baef589so16559195e9.0 for ; Mon, 12 Oct 2026 08:48:54 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1791820133; x=1792424933; darn=kvack.org; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:from:to:cc:subject :date:message-id:reply-to:content-type; bh=bz+XxQbQvV9Rkz3jiplflbfyEnwSo6hWkWyEVkUNcs8=; b=LtYFx8HdQ2REYW4nPO8u5qBv0LVqOVGh0HP+tuP3lBZXmRIhIFIO/qLchoPjeH8okk 32UrWa2FhvWEfxDgp3V6rIBkKMKP3MidmI/I3JaHLpNzbXZWxPJwsrBCz8F209wuI6dA TvQP9rBdbADIgR812biqsWEEMaitdoobgB2FY1YktMI3+MTD+ynmkm8aRGOLxTaaAO5u YF4Wz7eP4bc0Cxdsh/Xvmi+36A9t6Jyx3V/cLPIRbiaHQgb3VleSMHSAEz4XMFQhR7GE Nh9FUx56LjwDQEo/d8pohYZelT2fPcKAOsl2+dyl10vPE6uYr6bLa9FQbLfwSS/Ke69H xO4w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1791820133; x=1792424933; h=content-transfer-encoding:content-type:mime-version:references :in-reply-to:message-id:date:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=bz+XxQbQvV9Rkz3jiplflbfyEnwSo6hWkWyEVkUNcs8=; b=bu8jemwnA8EdatcAqSudGYTOBfkd4RuNmLWxSf0yorChA99amCvedoY/ueO9RLffbj FvCIopWOyuGarh2ALChgaYL1IkiBUaJlVRhec/p5r3rWzRo5tz3RZBx9+RswLVw7Ue4c sPHRvZY6SNxVXdKxWhPKfaD1mi7vqqo3BAOrbwuxO5s9l/6bJR4+rXek96DlpsZmcKRW uLuNB6jey7vJnruWXe3YTE0jHz95sR7USI9OyHnbTaCeUfJA7S0xDMSX3/UZt6jBDdrj 6YLaRdVr/fa1EWhCq14FK1vtN9P/A1sSPc7lGHfBmPK6LAPnFL0pVmbQkU7OODGol0Vn k3tg== X-Forwarded-Encrypted: i=1; AKwUvBz9vR/t9tPauNsl88FN/8rL59PHleYWa/u//TfH9rZhm7mHuVNfKG16MXloq92Wbja80qd3zfLstw==@kvack.org X-Gm-Message-State: AFq9FYKXvUaoyUHapalphSbzznHwn3XxWy+lkGgUNEadJLtIcfy/qOni wUFIqnZaAVZyqx5X4TU79AiY1wUHtuPFHfx9AYxk6MBqsM+dH5fcGrRw X-Gm-Gg: AYBFou3gn+jvDn60pThgaQV7vFXEDrf5BKV8yp4oSb2m+aDdE+Kz+uXwl5Y1rSO2J0X yqyl/rbKeJGpOPXdl+L/TMx2Co65B2jJzmLxsrB9caZ96M2obyP/udk1LH31HYPut8+xHGlGdnQ EovaQ3WQ5tBK404fAK7IYuMqLYnVddGTJASiBtW2BCxARV9TM5C93IljbbDvGoiV7BnSBhUrgjs +7wl4xjALYwEr7RGf1MocGJrG/tKYIb9vcKxt7Q628biIZ4u4qpnOzWeOVqUalDC2Y7Nek2Og5+ r1XToND8aSm7Tsy5QKZtyTGCXzufiJvDeDAiT+9HUbFo5J04VU8egQPycKUB4GX4J/3rN1mlR3g cFtXMIOPGxOd2rRLvo9uKhKTi6Bw+oM9EPZjHlGrNFxtBuOwapyBEOlEuMtzehUCyvlebxGLIFv 0r741f+x9xWI0Y7WhCqaejFoD0V+DYGpTPUHQ1UwRC3jjSqrqxSaNG4+uZivUlgxbgsJ9z+OHDh guXexjoZ/oFasZbbktMCofukl0KF4IcBQCHaSQ+iRU5XCDz+vn07d08x537pIJHSHmSJ8XFgg/L Q51f4nxJjfANKuRATt3AJAsaOzBcUglgJzo= X-Received: by 2002:a05:600c:699b:b0:4a0:4a8:d444 with SMTP id 5b1f17b1804b1-4a18e4af334mr195124235e9.33.1791820132890; Mon, 12 Oct 2026 08:48:52 -0700 (PDT) Received: from dev-dsk-fgriffo-1c-93421965.eu-west-1.amazon.com (54-240-197-234.amazon.com. [54.240.197.234]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4a193f2c992sm210228205e9.5.2026.10.12.08.48.51 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Mon, 12 Oct 2026 08:48:52 -0700 (PDT) From: Fred Griffoul To: Paolo Bonzini , Sean Christopherson , Marc Zyngier , Oliver Upton , Andrew Morton , David Hildenbrand , Alexander Viro , Christian Brauner , Jan Kara , Jason Gunthorpe , Kevin Tian , Joerg Roedel , Will Deacon , Robin Murphy , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H . Peter Anvin" , Jonathan Corbet , Shuah Khan , David Woodhouse , Ackerley Tng , "Aneesh Kumar K.V" Cc: Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Joey Gouly , Suzuki K Poulose , Zenghui Yu , Steffen Eiden , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, kvmarm@lists.linux.dev, iommu@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org Subject: Re: [RFC PATCH 0/9] mm: Memory providers for guest_memfd and iommufd Date: Mon, 12 Oct 2026 15:48:50 +0000 Message-ID: <20261012154850.96716-1-griffoul@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <0ae3d92ef99c264cfd76d3c1ddef357e96c98d93.camel@infradead.org> References: <20260720111259.122911-1-dwmw2@infradead.org> <20261006183235.16576-1-griffoul@gmail.com> <20261012095800.50250-1-griffoul@gmail.com> <20261012150715.25132-1-griffoul@gmail.com> <0ae3d92ef99c264cfd76d3c1ddef357e96c98d93.camel@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 92C5D18000A X-Rspam-User: X-Stat-Signature: ibmkjiwmrn4cbge4r4qkq7y9mwdq4gyt X-HE-Tag: 1791820134-28715 X-HE-Meta: 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 LsoAN8C6 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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 Mon, 2026-10-12 at 16:13 +0100, David Woodhouse wrote: > On Mon, 2026-10-12 at 15:07 +0000, Fred Griffoul wrote: > > Devices are different, because a device may not support > > faults. So the provider also revokes the range on the target once it > > owns the frames, and iommufd maps them right away. In other words, a > > revoke means that the frames behind a range changed, whether they went > > away or arrived. > > That would map to the IOMMUFD 'REPLACE' operation that hitlessly > replaces a PTE, but does anyone actually need that? No, not on the target. Before the move the child has nothing mapped in that range, so when the frames arrive iommufd just maps them. That is a plain map, not a REPLACE. > As I said, assume that the "crappy devices can't take faults and need a > scratch patch" issue is dealt with *elsewhere* and not relevant to the > guest_memfd/memprovider work. That's purely a quirk on a given IOAS > within iommufd. Agreed. The replace is only needed on the source, where the frames go away and a device that cannot fault must see the scratch page instead. With that quirk on the IOAS, iommufd does it, and the provider does not need to know about it. Thanks, Fred