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 2FBA7C4167B for ; Mon, 6 Nov 2023 15:56:09 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 923768E0007; Mon, 6 Nov 2023 10:56:08 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 8ACB68E0001; Mon, 6 Nov 2023 10:56:08 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 74CB48E0007; Mon, 6 Nov 2023 10:56:08 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 619F08E0001 for ; Mon, 6 Nov 2023 10:56:08 -0500 (EST) Received: from smtpin01.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay07.hostedemail.com (Postfix) with ESMTP id 366A61607C7 for ; Mon, 6 Nov 2023 15:56:08 +0000 (UTC) X-FDA: 81427980816.01.50EFB70 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) by imf08.hostedemail.com (Postfix) with ESMTP id 2AE8A16000F for ; Mon, 6 Nov 2023 15:56:05 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="aJ/kfI6k"; spf=pass (imf08.hostedemail.com: domain of 3lQxJZQYKCAQwierngksskpi.gsqpmry1-qqozego.svk@flex--seanjc.bounces.google.com designates 209.85.219.201 as permitted sender) smtp.mailfrom=3lQxJZQYKCAQwierngksskpi.gsqpmry1-qqozego.svk@flex--seanjc.bounces.google.com; dmarc=pass (policy=reject) header.from=google.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1699286166; a=rsa-sha256; cv=none; b=PLw+YLFYf5+LvzBg+CD4OFw63YVV9fmEXoq+S1ysoHZGGI3eL7BkCQESvGKOpEsHOFADN4 mLJ6F2eucBogGizcBOqJrFHRmhbw6jWOJ7Q5rLeFRTfN9jdEHtq8L5zCaS1uh+DAfY3x43 uKzffomrC0eegVLxT9m+P+43tVYt2pA= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=google.com header.s=20230601 header.b="aJ/kfI6k"; spf=pass (imf08.hostedemail.com: domain of 3lQxJZQYKCAQwierngksskpi.gsqpmry1-qqozego.svk@flex--seanjc.bounces.google.com designates 209.85.219.201 as permitted sender) smtp.mailfrom=3lQxJZQYKCAQwierngksskpi.gsqpmry1-qqozego.svk@flex--seanjc.bounces.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=1699286166; 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=2j2Mtk4lW9HEtWavGEnwteIJF5J/7dhiq9rSq3IBx+E=; b=Lxu7yHadiqEc40U6FlpDjBKUcarz66H+Lvv0+LesAMC02edtomRLA1OeK40yDs5hCRVGLG Z7J1uQ8XXZGy5wQ90Go0goVJgCWteB9IpeO2uWqu5WhWz4EP8Vux37ft2KayNFOQuckLLr U0DHvD4TjwRmgCpIh502ZiSLDmwTBG8= Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-da033914f7cso5367552276.0 for ; Mon, 06 Nov 2023 07:56:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1699286165; x=1699890965; darn=kvack.org; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:from:to:cc:subject:date:message-id :reply-to; bh=2j2Mtk4lW9HEtWavGEnwteIJF5J/7dhiq9rSq3IBx+E=; b=aJ/kfI6kUw0xsZnIDLBNEofF/LiieXwuiLxn6Artf+jMsk+5Q+xf0nSTiaN/QAcT24 tKStfj345RUe6ZwN/HpFHiwBXUjRyGPX2949ElQyigbcZ4HrVuCMRuBgadL8QsieN5VA /ZA3/RPFFoKc3Yt5/PHLLNMqtYjyEmr5aJIxYn/geaC8XpJNLGc954g1imAmlhkH84fB 3Vmc3WtZhhy46oKd793F5pTwt14tiR4zbefZd6UREoqvz35a/2dhlkPmlBnEm4TLH4qW yKyiNgk7Yveub4X+hktgv9ibiV5mnSdv8QijBt+5batPgnrc74hp65RYqBV2DwbLog/e +X8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1699286165; x=1699890965; h=content-transfer-encoding:cc:to:from:subject:message-id:references :mime-version:in-reply-to:date:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=2j2Mtk4lW9HEtWavGEnwteIJF5J/7dhiq9rSq3IBx+E=; b=vG+N6xy9S2qGrmDK+OZN/sNBiKSSmiHz2SRfoluKKzYutv1z819Sw/2O99Gdlb0A2b u245JZHNY2FutVGL8/2du/71zzoSTHa4zUg1GBUWwGS4eC/WdL4ycs7cpgf7+NsPLpYf iw/ArlhQnEOXceqpWxhT1mgpXwFrZsJZ6fCEktufDrPQ5mbsa284O3E/5pYZwbT0Uwj3 kxK97Lu7zWfGD4sDXs7wyFA9dJdD5RX+2TRhwloapG2g7BSvCVDAzFPhOmcwgwbe+g+W fvWSl9QbtipcjhmDdCNj72PpIV5upnE+ieFL2c1lpJnDs72U4AjVzIc9kPPlDRWkK3SV wlPA== X-Gm-Message-State: AOJu0YxFMSfPeOKKguPVm1FY2a63FKXllKPudk2tSnSQpQWBpDIhNxgZ +l1X+eN8KMbhH+hrNxw0t9sUjxmc3FU= X-Google-Smtp-Source: AGHT+IERk2b/M7d3G4J3vDGzrJ+T8jAsirv4bBIzvQT8OzuTMUe5AwPvC/SZu8YyGY6aMLoBT08jDOLmS/Y= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a05:6902:1083:b0:d9a:c3b8:4274 with SMTP id v3-20020a056902108300b00d9ac3b84274mr683795ybu.7.1699286165114; Mon, 06 Nov 2023 07:56:05 -0800 (PST) Date: Mon, 6 Nov 2023 07:56:03 -0800 In-Reply-To: Mime-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-21-seanjc@google.com> Message-ID: Subject: Re: [PATCH v13 20/35] KVM: x86/mmu: Handle page fault for private memory From: Sean Christopherson To: Xu Yilun Cc: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton , kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-mips@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Xiaoyao Li , Xu Yilun , Chao Peng , Fuad Tabba , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , "=?utf-8?Q?Micka=C3=ABl_Sala=C3=BCn?=" , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A . Shutemov" Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 2AE8A16000F X-Stat-Signature: k93pkyi5sgs6k3puoc6q5xhm8ahq7jeu X-Rspam-User: X-HE-Tag: 1699286165-890730 X-HE-Meta: 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 Mg3ibGf4 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 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 Mon, Nov 06, 2023, Xu Yilun wrote: > On Sun, Nov 05, 2023 at 05:19:36PM +0100, Paolo Bonzini wrote: > > On Sun, Nov 5, 2023 at 2:04=E2=80=AFPM Xu Yilun wrote: > > > > > > > +static void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcp= u, > > > > + struct kvm_page_fault *= fault) > > > > +{ > > > > + kvm_prepare_memory_fault_exit(vcpu, fault->gfn << PAGE_SHIFT, > > > > + PAGE_SIZE, fault->write, fault-= >exec, > > > > + fault->is_private); > > > > +} > > > > + > > > > +static int kvm_faultin_pfn_private(struct kvm_vcpu *vcpu, > > > > + struct kvm_page_fault *fault) > > > > +{ > > > > + int max_order, r; > > > > + > > > > + if (!kvm_slot_can_be_private(fault->slot)) { > > > > + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); > > > > + return -EFAULT; > > > > + } > > > > + > > > > + r =3D kvm_gmem_get_pfn(vcpu->kvm, fault->slot, fault->gfn, &f= ault->pfn, > > > > + &max_order); > > > > + if (r) { > > > > + kvm_mmu_prepare_memory_fault_exit(vcpu, fault); > > > > + return r; > > > > > > Why report KVM_EXIT_MEMORY_FAULT here? even with a ret !=3D -EFAULT? > >=20 > > The cases are EFAULT, EHWPOISON (which can report > > KVM_EXIT_MEMORY_FAULT) and ENOMEM. I think it's fine > > that even -ENOMEM can return KVM_EXIT_MEMORY_FAULT, > > and it doesn't violate the documentation. The docs tell you "what > > can you do if error if EFAULT or EHWPOISON?"; they don't > > exclude that other errnos result in KVM_EXIT_MEMORY_FAULT, > > it's just that you're not supposed to look at it >=20 > Thanks, it's OK for ENOMEM + KVM_EXIT_MEMORY_FAULT. >=20 > Another concern is, now 3 places to report EFAULT + KVM_EXIT_MEMORY_FAULT= : >=20 > if (!kvm_slot_can_be_private(fault->slot)) { > kvm_mmu_prepare_memory_fault_exit(vcpu, fault); > return -EFAULT; > } >=20 > file =3D kvm_gmem_get_file(slot); > if (!file) > return -EFAULT; >=20 > if (fault->is_private !=3D kvm_mem_is_private(vcpu->kvm, fault->gfn)) { > kvm_mmu_prepare_memory_fault_exit(vcpu, fault); > return -EFAULT; > } >=20 > They are different cases, and seems userspace should handle them > differently, but not enough information to distinguish them. For the first, the memory_fault exit will inform userspace that the guest w= ants to map memory as private, and userspace will see that the memslot isn't con= figured to support private mappings. Userspace may not even need to query memslots= , e.g. if the gfn in question has been enumerated to the guest as something that c= an only be mapped shared. For the second (no valid guest_memfd file), userspace put the last referenc= e to the guest_memfd file without informing the guest or creating a memslot. Th= at's firmly a userspace bug. For the third and last, userspace will see that the guest is requesting a p= rivate mapping but the gfn is configured for shared mappings. In all cases, userspace has the necessary information to resolve the issue,= where "resolving the issue" may mean terminating the guest. If userspace isn't t= racking memslots or the private attribute, then userspace has far bigger problems.