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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 3554BC3ABC3 for ; Mon, 12 May 2025 07:09:33 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 854AC6B00BC; Mon, 12 May 2025 03:09:31 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8034C6B00BE; Mon, 12 May 2025 03:09:31 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 67F586B00BF; Mon, 12 May 2025 03:09:31 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 468096B00BC for ; Mon, 12 May 2025 03:09:31 -0400 (EDT) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 3CEC71CCEDB for ; Mon, 12 May 2025 07:09:32 +0000 (UTC) X-FDA: 83433380184.17.94CE379 Received: from mail-qt1-f175.google.com (mail-qt1-f175.google.com [209.85.160.175]) by imf22.hostedemail.com (Postfix) with ESMTP id 68353C0006 for ; Mon, 12 May 2025 07:09:30 +0000 (UTC) Authentication-Results: imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=XhlbklIv; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf22.hostedemail.com: domain of tabba@google.com designates 209.85.160.175 as permitted sender) smtp.mailfrom=tabba@google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1747033770; 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=XSmTOYCiVv7/OshHrbhVrhF4ObIKGNu6xZWV2038bpM=; b=yy77mK9R0Lx/wNpR0GTRF71hQ4T6REdsgea7rSssRAUPLI2H0kNkfOVOZiVBY0jpGo2WNH Y9IR/Xey+pPMqEeIa1yvwOSkdzKWfkTd2qiebSMwe8l2kWkWU5Myw/zeqQ8vBrrpDGZyRh E+ja8NPq2H1dafiP1QtLWYXgEsd8JKo= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1747033770; a=rsa-sha256; cv=none; b=u50rF4l3+d3dAk+fJAUUR19Gx/hh4brBoYcaRCaCapuo3WsqCIVlKqHXIaM2vubCtbJpmi 1HeB6DaXf5+iKSgqaFRxWzQEGCCTsRVPJszZWjHq4bE65MTbmZAMI/wXxI+e7WOeXf2i5D moa61JFs0WmzhfYfmd9Q9dCr8hEh+Tw= ARC-Authentication-Results: i=1; imf22.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=XhlbklIv; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf22.hostedemail.com: domain of tabba@google.com designates 209.85.160.175 as permitted sender) smtp.mailfrom=tabba@google.com Received: by mail-qt1-f175.google.com with SMTP id d75a77b69052e-47e9fea29easo570751cf.1 for ; Mon, 12 May 2025 00:09:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1747033769; x=1747638569; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=XSmTOYCiVv7/OshHrbhVrhF4ObIKGNu6xZWV2038bpM=; b=XhlbklIv0S1kE1huVQqr3gRTVVVaLDjAIk1cc76Pm32tnqrI7tR/YONKlxIy7xGxUz Uo+UsdBNsAG2Lhs2aoDDQQ6gO1HEZI+LWlwrsCiFnWHSbynlvbV335tz6YT3AS80NpsT HAiaiqIEwJyfAQZBXANe9aHiVq7E7XM6YZFINul71AhWUZbtusM52p676q6a3ZIzqJy+ B092BJfO/bu0gBZcHVlvFN3D/2ahPaIK7K4qsqtyB8mPlIP+5MBcAfCBHHbfKD5JjsZl Kp4AmRV00SG2YBVERMuLCxFJFmdAm//NNsX6AScbMlzPvygtqaGg7UuMQaYnVw987Lx0 2I2w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1747033769; x=1747638569; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=XSmTOYCiVv7/OshHrbhVrhF4ObIKGNu6xZWV2038bpM=; b=aLaOpzJKxZTnOQRTHYPOayjPYZMKwfIc45VD2WnC9q3L8HUWvVnBRj/6j22iwnevcV feqAYuS+nWe30QFpq1YdgqdCxfTwJ6eAo8i+I1+nGksC0ioakfB58Q3uLY88EFWRAtXG whrX6dh4/NywqyDnebG7CGR8sD9kGuApmSCDTdECs9hV0HTfj7o8h1ETL9ETP9MkGJ3s 7SXmxH9lt65Qyz5lQapNfbiGUNYlzUajoDGkTNaSI4Fcr2vl09tWSUpcGqtLdUGItZM7 CCeYlZcfF3H+o+kGjBgPuEVA5QcQz4eFsS/U5uLoYbwKAbooKs8SdeDMMtlA1H41cEC3 XMNw== X-Forwarded-Encrypted: i=1; AJvYcCVwSwCmLnJK7p0Pdgc85qd69QaNTHi37QW0rgFVqFz7uv3bGPmOTUJFOjxO+DAxXhvfHMLm79ymwg==@kvack.org X-Gm-Message-State: AOJu0YyjskR1RQn1dEfic/u1npoK20qaRmAsIKwy9XLyHZXoXS7ON4Hx egWg1JcHz26fYoIeGdhOUpipUB9P4j/MZgPqths0I1JhtzzIadJ0GFjuUTsWnJUHHlCkaBgWddB BBJC66r7So2wpmzSlB14hZ/C7e1C8YplAm7M8 X-Gm-Gg: ASbGncsn7OraDFY3OfmpwhCMmZN1IySZr9imG1eKLqwALfNDIkiOROn6xOsYW6lfa/g At/Z+v71cYepghIRXg4w0MnQWI7j12BbjncVOS7iBPG/FkVODH5gQJ5DnHNzb0BjP27McIjaQGG jeeyopmcLExdhhIJ6GNCpE/ehyDdlR4Qwtw64DTt5c+wxS X-Google-Smtp-Source: AGHT+IFWkn43x0P4nlxGLXdV3CrSVT40wPdseY7NOjafRyvqEjQ9QNxnsrVcDogvYXeKprPQ5Mqc/SYgP14o+2RK6eY= X-Received: by 2002:ac8:5889:0:b0:494:5923:8bcd with SMTP id d75a77b69052e-49462d40c04mr6781711cf.3.1747033769418; Mon, 12 May 2025 00:09:29 -0700 (PDT) MIME-Version: 1.0 References: <20250430165655.605595-1-tabba@google.com> <20250430165655.605595-9-tabba@google.com> <702d9951-ac26-4ee4-8a78-d5104141c2e4@redhat.com> In-Reply-To: <702d9951-ac26-4ee4-8a78-d5104141c2e4@redhat.com> From: Fuad Tabba Date: Mon, 12 May 2025 08:08:52 +0100 X-Gm-Features: AX0GCFv-MyXwz1MDe12JSf9b8ojiBGKwn87SyNuOsfPf6zdJXpwsIjIp3k07lFM Message-ID: Subject: Re: [PATCH v8 08/13] KVM: guest_memfd: Allow host to map guest_memfd() pages To: David Hildenbrand Cc: James Houghton , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, peterx@redhat.com, pankaj.gupta@amd.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: fycpmriof98j8w3d5xz3smzfti7dhdiy X-Rspam-User: X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 68353C0006 X-HE-Tag: 1747033770-73734 X-HE-Meta: U2FsdGVkX1933tUfkx0fXfjkE/i2+P+ZePyjZIKhva+jBQVk8DkHeXyi9DRsNTgToNUWXmvYoGuB6rAaFe/Vg+X+NSDzOToGM1ktdxbZLDB1mWuqlXxNTAVxeSARuMTFKWzVC7CVwvR1PDbNjPBkhUQepeu4kF/yK82fmhq2F+atppvCSAYh2ykQ539oQWcGnCDcZJM1eCMAA5BmxYQzREf1xq172HkqTWs/xUMGftbllFXrdT71oRgYE2VMmeqFQCqJecBQE6J3cIpcVhjKxghqYFs7MZ3Izz1WfC392g5z90qLD0h5xka2/d6c4TcAyWE9oHfC9nmHH6oVpqcOXXKOsRmhSBeLGTRyc5UCPkjaW2quVkf1gmhuX9NGVUwyVOv800zHRPZUvtheI4whqf5AHMlEjFPAZrOfyPILviBzbEhUoq4d10SVmU3ed2k83KW6/WJBhlGeB76nDQ8XOrc88kGYFr00L5b7GT/92LlvzYOA3dnV9f03GTzXCuR0v2uQQOHn0rVgU1mmYizgDm0h2G2xQHFIiHrKy4TQ391eIqsVBd10fBh1cMrmMSBmuIFBvFHSnu/Rc/0Eu6PGj5OPjsSFcCLF+7++VWQ1BHTejIbudo+dpM5YT9sdZ4BZ4UjQWfljA0tkBQgL+1tACznoRvJxYSdql8bKf/tjKFep9KcVZMtKnPYa7gAQ6mHTb01flkGx5kOcWFc9OUYrCVqUQAm6HR6vsaUVnWXmFQ96zw4vaZ5YZcO5AhHuze+vuaK/VdOV6JQgYM/LIYptjYn5k4EL1SiZmd9URGvR8iZm72WiOosw/brVVew3DuOztB+gw4PHETZKg/XjIe0/rYyP/vAdrK144SbJZB0smZsY9M58xgWUkkLGOvVjUd8faOTERvKo4d7Tyf/d9Tz8UwqVjOa2jti6j8kSYxDLoBsRcU7Ra2zN+CuOmHZF1ydiIMsmEXJQ5uROXO2ofVL eT0EP4V0 3Pt5U+mMKLseP/lkNQfYQM9q13NhN63VylMZwcerEVsAfx2R1IfDLClllU6rpKZSJZSi3KzDuk55VmFiQ997zvsVSZZWiyxsOSOELmM3G9vW1iLLJ9Qp9aqKJkuxENRh5Lm3BrMpOcFQRpT1xwHAP2ZpbTySzZ0LZ+TE86SHLzfotezCuLstMQ3DNlSBSakk+btqfUWmwrRcdqyO+LYeiFjf205gP46jX8tfrnPu4tlr9oicYsnSs5Uuy9gvtr17v7XBFXOVpTLj86vtn8ch6GXC/haFllfWN1GRZHeGZxhYyEF6/PtHNpl44o1p8w8GNVcW9OCQiUFy+N6e84jBqoGDARRFixwlnQqkIkgQ3JpcwFpU= 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: List-Subscribe: List-Unsubscribe: Hi James. On Sun, 11 May 2025 at 09:03, David Hildenbrand wrote: > > On 09.05.25 22:54, James Houghton wrote: > > On Wed, Apr 30, 2025 at 9:57=E2=80=AFAM Fuad Tabba w= rote: > >> +static int kvm_gmem_mmap(struct file *file, struct vm_area_struct *vm= a) > >> +{ > >> + struct kvm_gmem *gmem =3D file->private_data; > >> + > >> + if (!kvm_arch_gmem_supports_shared_mem(gmem->kvm)) > >> + return -ENODEV; > >> + > >> + if ((vma->vm_flags & (VM_SHARED | VM_MAYSHARE)) !=3D > >> + (VM_SHARED | VM_MAYSHARE)) { > >> + return -EINVAL; > >> + } > >> + > >> + vm_flags_set(vma, VM_DONTDUMP); > > > > Hi Fuad, > > > > Sorry if I missed this, but why exactly do we set VM_DONTDUMP here? > > Could you leave a small comment? (I see that it seems to have > > originally come from Patrick? [1]) I get that guest memory VMAs > > generally should have VM_DONTDUMP; is there a bigger reason? > > (David replying) > > I assume because we might have inaccessible parts in there that SIGBUS > on access. That was my thinking. > get_dump_page() does ignore any errors, though (returning NULL), so > likely we don't need VM_DONTDUMP. In which case I'll remove this from the next respin. Thanks, /fuad > -- > Cheers, > > David / dhildenb >