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 E3FF4C02182 for ; Thu, 23 Jan 2025 11:02:53 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 7431F280003; Thu, 23 Jan 2025 06:02:53 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6D2BC280001; Thu, 23 Jan 2025 06:02:53 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 56DD3280003; Thu, 23 Jan 2025 06:02:53 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 38010280001 for ; Thu, 23 Jan 2025 06:02:53 -0500 (EST) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id E3AA7C0F2C for ; Thu, 23 Jan 2025 11:02:52 +0000 (UTC) X-FDA: 83038428984.19.0520A2E Received: from mail-qt1-f170.google.com (mail-qt1-f170.google.com [209.85.160.170]) by imf20.hostedemail.com (Postfix) with ESMTP id 176451C000D for ; Thu, 23 Jan 2025 11:02:50 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=4X5OrACw; spf=pass (imf20.hostedemail.com: domain of tabba@google.com designates 209.85.160.170 as permitted sender) smtp.mailfrom=tabba@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1737630171; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=534qKq2nBqfa72deztRkj55ApSevdTMjZbwAxpL0RdM=; b=sgQQ49zy5bJoJO0c50QD9FVOKK6ITXe0FD5iV/GcY04zQQgnWSTD0Xm6SOwXgRVtFowMHb 6bk1itRNzoczrWFojRlFuvVjFWpli6kd10n8QcdeyeuLIxPkJu/m6RunjBzjd4mEV5rZYJ rwmAEPlqrd/eWwZ8U07LZk9K3fjkDDc= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=4X5OrACw; spf=pass (imf20.hostedemail.com: domain of tabba@google.com designates 209.85.160.170 as permitted sender) smtp.mailfrom=tabba@google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1737630171; a=rsa-sha256; cv=none; b=aJbCLXJjp+GAu9bxQASfkFgW4CYEY0mYqv3COeQLI0YGMYI2v5gNQCjf+3L2d5Aa0QFJmK EpLhL4s45pbZr/7M8OFB/oZ0wklMgOoUIU4AqnXQf7QAmDX7e/QSAfgt4cczS+tDTC9Ab9 knYrSLJ0glFKPLyThB90PyQhDUktZAg= Received: by mail-qt1-f170.google.com with SMTP id d75a77b69052e-4679b5c66d0so164941cf.1 for ; Thu, 23 Jan 2025 03:02:50 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1737630170; x=1738234970; darn=kvack.org; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=534qKq2nBqfa72deztRkj55ApSevdTMjZbwAxpL0RdM=; b=4X5OrACwAiHvl5617W4WW1URGGA93TvCi9xleE8WwxAo0pFe9uiDgxaMFq48RaY3tm ONysSgpuJpabKAQe/dC4QxNfdJl5/z/Ha1Tol2ses2qSOErg9/MUVDOSJWB8OemnwyGx fwxG5ynQVmk7NWIAM5RPm/mvNcEzWaB7l2I9EEBH6sAZirowHJmqMtAG+ENA6KRu8hCn ZJHmxMW9jqokiRRZsohelpvtmcZ8BtquKonn5M3XXOAsVlhui8hrGaadTyXf7/2CxJqd CRBfP2Yb5Y0+pklAix6jkfnuMKQKUUeM9c5Ud9vvj+sTxAyJmVnUn7AMMw89sxBW3OQ2 medw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1737630170; x=1738234970; h=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=534qKq2nBqfa72deztRkj55ApSevdTMjZbwAxpL0RdM=; b=BwtB11aWm4fxbelrVymEK7TpFotzm+iOqvUc3WMEVCMRb+Ju2FitcQndkA3OhD+AuV JbzedeGnewGmRPYqeJ+PEv7vb/fykuJp51LdgVnmzuLZ+z27OWUkpOw/f/WYSlLWR3R5 ez57OOYv2fpCOGVotDQS4DDXZx0Ad9lBqdt1FI4lpY0lLRcfq0BGsop+LSTgHFBuqTyy zBp5MQi6h0srDx04MPP1yGr6sh6NWGwrQzoJgj7GcavZfgocicm1n9eJiuk1XjAOSFCq lYgarSU/OvlVNhhw7qzCdsQ27rGa/zcVVfoUwCD7+MNgO0kgVlkouk5Q3pbxkBSv0ERN WFZw== X-Forwarded-Encrypted: i=1; AJvYcCUHKragNAUBasfOpGY8QF9VVanFxhAA0l8Htck9aWGNIsgH5/mfa2F3K49nrJsW1dR1P4VPvjPJAw==@kvack.org X-Gm-Message-State: AOJu0YwakIcBcUYGaDojickDONjlsjFFgq0NiVLkqK1qtyGT+1QLk8/O fayCg5e2bVIgkcT4ay8qKFYhJ9p0k+pocg0PSmW4l1PBhJy3gIyF+kMg4WcpppEvQZPc1gYCa2X JlVOE23Xw+LdZtWOs9hC7eF+ulNyoSY6sVi41 X-Gm-Gg: ASbGnctqmIgdVs8DAoXYeCo8Qjy6xS+JnSe/mABHyFwke8AYMpaREk/Jk2m2rLQzESc qUL11op1hwAuSh6rsnEwTzx7NQc1e+tZ/P69K4v48uMTXFqitnUJR1SLCUCLyfcxMW2gTOxM54O WYMKg7uPeMtHbPcg== X-Google-Smtp-Source: AGHT+IE5A0w2L1X658+LHB+HyANHlVbiZyxxn5KgmXf+b2y2M19U2pR8HBDe43GiSVDq5CUFfSxQSwUh+0yGvl72/Pg= X-Received: by 2002:a05:622a:2b04:b0:466:a11c:cad2 with SMTP id d75a77b69052e-46e5dac8664mr2664671cf.7.1737630169569; Thu, 23 Jan 2025 03:02:49 -0800 (PST) MIME-Version: 1.0 References: <20250122152738.1173160-1-tabba@google.com> <20250122152738.1173160-2-tabba@google.com> <647bbdac-df82-4cdb-a3e9-287d439b4ef7@redhat.com> In-Reply-To: From: Fuad Tabba Date: Thu, 23 Jan 2025 11:02:12 +0000 X-Gm-Features: AWEUYZnu-D_Bl2EeCiXhDS-e4549NCyPHJb7KJVcA8GOOTXtl1qu8IfoC4op6eE Message-ID: Subject: Re: [RFC PATCH v1 1/9] KVM: guest_memfd: Allow host to mmap guest_memfd() pages To: David Hildenbrand Cc: 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, yu.c.zhang@linux.intel.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, jthoughton@google.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: 176451C000D X-Stat-Signature: 8dtmq7cd6w3z7c4st8yhkg6t4k715n6t X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1737630170-540501 X-HE-Meta: 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 o7h2u7mk rg5uOUHCdlAww+PM8vsfJhOJ8wKj4i855A49ZI5NXn5uuuJkn0S1Pv3qDPoYAWbyHnCrcf3p22/+O/N2J50UJ47cz07LrIEMPT1CAu/0uEn7GGWcDK0MN+/q5OMZYXrQvvLEXlFeFD4ya52Y44OFf0BBAGbPRFC7XZn1IVRRqrvl2RdKerJjv6W84SUJk5hkch9PQP3cdsXnOrTWE6F3rEE+YLtarvekEb786XGmTz1RSqEFWy+7zW7fIj3BmqaviYZIzmCJmzQH32kt/R3hDgcuxJxry11VGx4HXPx2Nnvfnd0E1kjx2Iq1vmAEHH66XLZD1f4o8CEsb+bClUsrB12EIoU4DSenic0j2TGrr21OX28npUREDe6fM9/C5YUaAo00x 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: On Thu, 23 Jan 2025 at 10:28, David Hildenbrand wrote: > > >>> + bool > >>> diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > >>> index 47a9f68f7b24..9ee162bf6bde 100644 > >>> --- a/virt/kvm/guest_memfd.c > >>> +++ b/virt/kvm/guest_memfd.c > >>> @@ -307,7 +307,78 @@ static pgoff_t kvm_gmem_get_index(struct kvm_memory_slot *slot, gfn_t gfn) > >>> return gfn - slot->base_gfn + slot->gmem.pgoff; > >>> } > >>> > >>> +#ifdef CONFIG_KVM_GMEM_MAPPABLE > >>> +static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) > >>> +{ > >>> + struct inode *inode = file_inode(vmf->vma->vm_file); > >>> + struct folio *folio; > >>> + vm_fault_t ret = VM_FAULT_LOCKED; > >>> + > >>> + filemap_invalidate_lock_shared(inode->i_mapping); > >>> + > >>> + folio = kvm_gmem_get_folio(inode, vmf->pgoff); > >> > >> > >> Would the idea be later that kvm_gmem_get_folio() would fail on private > >> memory, or do you envision other checks in this code here in the future? > > > > There would be other checks in the future, the idea is that they would > > be the ones in: > > https://lore.kernel.org/all/20250117163001.2326672-8-tabba@google.com/ > > > > Thanks, so I wonder if this patch should just add necessary callback(s) > as well, to make this patch look like it adds most of the infrastructure > on the mmap level. > > kvm_gmem_is_shared() or sth like that, documenting that it must be > called after kvm_gmem_get_folio() -- with a raised folio reference / > folio lock. > > Alternatively, provide a > > kvm_gmem_get_shared_folio() > > that abstracts that operation. > > We could also for now ensure that we really only get small folios back, > and even get rid of the clearing loop. > > > The "WARN_ON_ONCE(folio_test_guestmem(folio)" would be added separately. > > In the context of this series, the callback would be a nop and always > say "yes". I agree, especially if this patch series were to serve as a prelude to the other one that adds restricted mmap() support. Cheers, /fuad > -- > Cheers, > > David / dhildenb >