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 AF591C0218F for ; Fri, 31 Jan 2025 09:11:57 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 2E5D22802A5; Fri, 31 Jan 2025 04:11:57 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 226DD280299; Fri, 31 Jan 2025 04:11:57 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 04D2C2802A5; Fri, 31 Jan 2025 04:11:56 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id D9FD6280299 for ; Fri, 31 Jan 2025 04:11:56 -0500 (EST) Received: from smtpin28.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 82488B05F2 for ; Fri, 31 Jan 2025 09:11:56 +0000 (UTC) X-FDA: 83067179832.28.C01AB6A Received: from mail-qt1-f169.google.com (mail-qt1-f169.google.com [209.85.160.169]) by imf09.hostedemail.com (Postfix) with ESMTP id A40A2140017 for ; Fri, 31 Jan 2025 09:11:54 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=SNaXPT+B; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf09.hostedemail.com: domain of tabba@google.com designates 209.85.160.169 as permitted sender) smtp.mailfrom=tabba@google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1738314714; a=rsa-sha256; cv=none; b=AftEv6CdiDzpDRFIS6PDBgsRq2h96npPgYAfTvbQpFZoUu2TL+NHflSklDP3Kp9rweweVu s61opF6kalppHF1guzaW+ZZOqnmuKuTiTAdScgcbb2kaHxvs3AqtQG4xXBAKCitvjfNOI4 RPaKQja2eHF41ieBYsg9rIs9JUsIvx8= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b=SNaXPT+B; dmarc=pass (policy=reject) header.from=google.com; spf=pass (imf09.hostedemail.com: domain of tabba@google.com designates 209.85.160.169 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=1738314714; 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=V8viV2JIhS0YcyIbIBjf/TReqK6Sasfiya5dHNECPVQ=; b=6T3clRD/1Ua/jJWV339ND9W+MneLp01YpkQCQ4ZtM+IdmhM152oUnVIeWETQNK3nzop9Ts VX2Iwi2DTFoGdmS7RbOqhwr5pVhHviq2TQi60jEWlGJyy4r9iBPVG37F0xON32AAvy/fq8 4XDFJLIhhwaxz9wQFursQ/+NjJZKrv0= Received: by mail-qt1-f169.google.com with SMTP id d75a77b69052e-467abce2ef9so174741cf.0 for ; Fri, 31 Jan 2025 01:11:54 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1738314713; x=1738919513; 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=V8viV2JIhS0YcyIbIBjf/TReqK6Sasfiya5dHNECPVQ=; b=SNaXPT+BFvWKrkCoTQ21aEWY2moxGVlAR0EtzmYBgmz7XQ3UtzFbM4pQztfrAW+mHb U0Ytz6UqawnDnQiUymHIOjpfTcuQwjBn9Ib1A+u/Pee7Adw8xPjH/kePiXtwxK8o69yI xLGWQ0VcbGXFMCiL+KVB5f2wb0Gc1ZNjyqwrxFXOVrA4mlb+9u2xmlToJouWwS7G3Ex6 +zIktttJshrEQbZWxqzXQdpz7Gjiref4Bs6V5zhHs2geogfJFqgPdaDhITKMGzaWEGh9 fkFJjyuPhH6Gs3on3fNDYal0pYdu4fgv4z2QMUxXIkwFhyJVK3aYe12+cpQS8v+KE43b CMmg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1738314713; x=1738919513; 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=V8viV2JIhS0YcyIbIBjf/TReqK6Sasfiya5dHNECPVQ=; b=QVk1Rh2fCUR9iasR/5bWDK8rlFOS7+g0HixaW9aQdlQr/wPw8d6T0rkJiQA7QjhsQk RP7yry/FdQ+ZDqSJV5l4jDNtCpInMkMMzRAq0QMlJlKxosz7RcbavzeJPqEMuBf6K7+H pWuN6ajnDn/HHYMnKWWmbMOW4+eyk9Dzz9ySx9NYur7YeQYi7K+hyByddKpiJx554QTu N1ctmG+qOg/g8du6nYQHRXypK7bmSCcz8RMQc3lF3P1SvblwQpIDWlisowIHPdhNlNyU Mxjg/7O35kv/ZrOklQNH3n09XyHyYxmN46g09E5Jf/+1FTZhn2I42WmRpPTDiJ+6ddH4 94Hg== X-Forwarded-Encrypted: i=1; AJvYcCWJ0UjmDMqYpo2jNrBB9UrjlWwF2bo0fqA3prVsCbogGw842+eclqYmK2z/Nwc8l9yFTSpSwht/yA==@kvack.org X-Gm-Message-State: AOJu0YxJhLY+G9ZwxA9O1BH97w8EKITzPIPEDRCyddCseN34TfPFEGIK jRLgXj/x+1atMtcs0Nig4lquMdUcmVMcF7so++XkLYJ0An62AsDjuMtpt+sIzzPO4Gs/z6xToxx GA2qdy+xgRpavY+n96y42ucq/4f9za+vnD1bvpTNSIoaADxAanf4E X-Gm-Gg: ASbGncsEG9jS/ryQu/DfjNuuz+wG3FFi3ZY9Kr1oxWa9hfVA/g+5DUvGP6eWARhHZvM QwJ2iNNwBxvMV9l5A0CZc8nh37FOuk2iL62wFFdudQXoIXDbmSlCfn3J0iwAu1wwHkgtOA6E= X-Google-Smtp-Source: AGHT+IHVEC2s9ki9SQQ/W6ZhPJlLd8vEs50C7zvNlKQG5KfH9Ht7+OxW856Y8WrT5oyxgdpTdK0yVT/Q5aY+XBzx+TU= X-Received: by 2002:a05:622a:5d1:b0:46c:791f:bf46 with SMTP id d75a77b69052e-46febfb595cmr1645811cf.19.1738314713185; Fri, 31 Jan 2025 01:11:53 -0800 (PST) MIME-Version: 1.0 References: <20250129172320.950523-1-tabba@google.com> <20250129172320.950523-4-tabba@google.com> <07e7e09a-997e-444e-92bf-8f2359a36cbd@redhat.com> In-Reply-To: <07e7e09a-997e-444e-92bf-8f2359a36cbd@redhat.com> From: Fuad Tabba Date: Fri, 31 Jan 2025 09:11:16 +0000 X-Gm-Features: AWEUYZnOe3bQNC7A_KGszwSxryeZBFYHbPkhnVOeAKu5tArSj7xEMUozbMTEOn8 Message-ID: Subject: Re: [RFC PATCH v2 03/11] KVM: guest_memfd: Allow host to map 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-Rspam-User: X-Rspamd-Queue-Id: A40A2140017 X-Rspamd-Server: rspam10 X-Stat-Signature: 9c48abnyn3r4gmgjyxy3c5hdy84ydw4u X-HE-Tag: 1738314714-730516 X-HE-Meta: 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 Kh+qxwJV fptE7od729GljoI2nzwB2P1ZdsLNgdehPcVzb39Pcvzev5KEg2aDrJdmcr/Ms98ueeP9wELcgpKD0KVOKiA785AVidyxGjeNnOCNIMtc45ma/vogz8ozaJ+YYfEG10uFPwedJg9VHRCjvTD71109l7YrMjohSpf0eG4E3fiYCacOzRt8zL91Xv2Q3kjBYmGPyOSgjGk/C/9Pa1TvYt4dGzxZ+aG46aacFySrnLfrqSILQg/We7+B6BeEnSvpEztxAY7GZSpgOr4e1S1lnZT+taxtssfYG3WYwgKEIucFwGvrmvWaVXR4rwOBJmoJeeAJ7AzDgYNj0+dHzI8+Bj/TmNF0S3+5p2Ln0LPl21DCC0Gb+sk0= 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 David, On Thu, 30 Jan 2025 at 17:20, David Hildenbrand wrote: > > On 29.01.25 18:23, Fuad Tabba wrote: > > Add support for mmap() and fault() for guest_memfd backed memory > > in the host for VMs that support in-place conversion between > > shared and private (shared memory). To that end, this patch adds > > the ability to check whether the VM type has that support, and > > only allows mapping its memory if that's the case. > > > > Additionally, this behavior is gated with a new configuration > > option, CONFIG_KVM_GMEM_SHARED_MEM. > > > > Signed-off-by: Fuad Tabba > > > > --- > > > > This patch series will allow shared memory support for software > > VMs in x86. It will also introduce a similar VM type for arm64 > > and allow shared memory support for that. In the future, pKVM > > will also support shared memory. > > --- > > include/linux/kvm_host.h | 11 ++++++ > > virt/kvm/Kconfig | 4 +++ > > virt/kvm/guest_memfd.c | 77 ++++++++++++++++++++++++++++++++++++++++ > > 3 files changed, 92 insertions(+) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 401439bb21e3..408429f13bf4 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -717,6 +717,17 @@ static inline bool kvm_arch_has_private_mem(struct kvm *kvm) > > } > > #endif > > > > +/* > > + * Arch code must define kvm_arch_gmem_supports_shared_mem if support for > > + * private memory is enabled and it supports in-place shared/private conversion. > > + */ > > +#if !defined(kvm_arch_gmem_supports_shared_mem) && !IS_ENABLED(CONFIG_KVM_PRIVATE_MEM) > > +static inline bool kvm_arch_gmem_supports_shared_mem(struct kvm *kvm) > > +{ > > + return false; > > +} > > +#endif > > + > > #ifndef kvm_arch_has_readonly_mem > > static inline bool kvm_arch_has_readonly_mem(struct kvm *kvm) > > { > > diff --git a/virt/kvm/Kconfig b/virt/kvm/Kconfig > > index 54e959e7d68f..4e759e8020c5 100644 > > --- a/virt/kvm/Kconfig > > +++ b/virt/kvm/Kconfig > > @@ -124,3 +124,7 @@ config HAVE_KVM_ARCH_GMEM_PREPARE > > config HAVE_KVM_ARCH_GMEM_INVALIDATE > > bool > > depends on KVM_PRIVATE_MEM > > + > > +config KVM_GMEM_SHARED_MEM > > + select KVM_PRIVATE_MEM > > + bool > > diff --git a/virt/kvm/guest_memfd.c b/virt/kvm/guest_memfd.c > > index 47a9f68f7b24..86441581c9ae 100644 > > --- a/virt/kvm/guest_memfd.c > > +++ b/virt/kvm/guest_memfd.c > > @@ -307,7 +307,84 @@ 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_SHARED_MEM > > +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); > > + if (IS_ERR(folio)) { > > + ret = VM_FAULT_SIGBUS; > > + goto out_filemap; > > + } > > + > > + if (folio_test_hwpoison(folio)) { > > + ret = VM_FAULT_HWPOISON; > > + goto out_folio; > > + } > > + > > Worth adding a comment, something like > > /* > * Only private folios are marked as "guestmem" so far, and we never > * expect private folios at this point. > */ > > + if (WARN_ON_ONCE(folio_test_guestmem(folio))) { > > + ret = VM_FAULT_SIGBUS; > > + goto out_folio; > > + } > > + > > + /* No support for huge pages. */ > > + if (WARN_ON_ONCE(folio_nr_pages(folio) > 1)) { > > + ret = VM_FAULT_SIGBUS; > > + goto out_folio; > > + } > > + > > /* We only support mmap of small folios. */ > VM_WARN_ON_ONCE(folio_test_large(folio)); Will do. Thanks. /fuad > > > + if (!folio_test_uptodate(folio)) { > > + clear_highpage(folio_page(folio, 0)); > > + folio_mark_uptodate(folio); > > + } > > + > > + vmf->page = folio_file_page(folio, vmf->pgoff); > > + > > Apart from that LGTM. > > -- > Cheers, > > David / dhildenb >