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 X-Spam-Level: X-Spam-Status: No, score=-7.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 8A23FC43381 for ; Fri, 22 Feb 2019 17:12:19 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 445CD2070D for ; Fri, 22 Feb 2019 17:12:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727369AbfBVRMS (ORCPT ); Fri, 22 Feb 2019 12:12:18 -0500 Received: from mx1.redhat.com ([209.132.183.28]:56832 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725942AbfBVRMR (ORCPT ); Fri, 22 Feb 2019 12:12:17 -0500 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id A264681E13; Fri, 22 Feb 2019 17:12:16 +0000 (UTC) Received: from [10.36.112.23] (ovpn-112-23.ams2.redhat.com [10.36.112.23]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CB5F360BF1; Fri, 22 Feb 2019 17:12:13 +0000 (UTC) Subject: Re: [PATCH] x86/kvm/mmu: fix switch between root and guest MMUs To: Vitaly Kuznetsov , kvm@vger.kernel.org Cc: =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Junaid Shahid , linux-kernel@vger.kernel.org References: <20190222164501.13605-1-vkuznets@redhat.com> From: Paolo Bonzini Openpgp: preference=signencrypt Autocrypt: addr=pbonzini@redhat.com; prefer-encrypt=mutual; keydata= mQHhBFRCcBIBDqDGsz4K0zZun3jh+U6Z9wNGLKQ0kSFyjN38gMqU1SfP+TUNQepFHb/Gc0E2 CxXPkIBTvYY+ZPkoTh5xF9oS1jqI8iRLzouzF8yXs3QjQIZ2SfuCxSVwlV65jotcjD2FTN04 hVopm9llFijNZpVIOGUTqzM4U55sdsCcZUluWM6x4HSOdw5F5Utxfp1wOjD/v92Lrax0hjiX DResHSt48q+8FrZzY+AUbkUS+Jm34qjswdrgsC5uxeVcLkBgWLmov2kMaMROT0YmFY6A3m1S P/kXmHDXxhe23gKb3dgwxUTpENDBGcfEzrzilWueOeUWiOcWuFOed/C3SyijBx3Av/lbCsHU Vx6pMycNTdzU1BuAroB+Y3mNEuW56Yd44jlInzG2UOwt9XjjdKkJZ1g0P9dwptwLEgTEd3Fo UdhAQyRXGYO8oROiuh+RZ1lXp6AQ4ZjoyH8WLfTLf5g1EKCTc4C1sy1vQSdzIRu3rBIjAvnC tGZADei1IExLqB3uzXKzZ1BZ+Z8hnt2og9hb7H0y8diYfEk2w3R7wEr+Ehk5NQsT2MPI2QBd wEv1/Aj1DgUHZAHzG1QN9S8wNWQ6K9DqHZTBnI1hUlkp22zCSHK/6FwUCuYp1zcAEQEAAbQj UGFvbG8gQm9uemluaSA8cGJvbnppbmlAcmVkaGF0LmNvbT6JAg0EEwECACMFAlRCcBICGwMH CwkIBwMCAQYVCAIJCgsEFgIDAQIeAQIXgAAKCRB+FRAMzTZpsbceDp9IIN6BIA0Ol7MoB15E 11kRz/ewzryFY54tQlMnd4xxfH8MTQ/mm9I482YoSwPMdcWFAKnUX6Yo30tbLiNB8hzaHeRj jx12K+ptqYbg+cevgOtbLAlL9kNgLLcsGqC2829jBCUTVeMSZDrzS97ole/YEez2qFpPnTV0 VrRWClWVfYh+JfzpXmgyhbkuwUxNFk421s4Ajp3d8nPPFUGgBG5HOxzkAm7xb1cjAuJ+oi/K CHfkuN+fLZl/u3E/fw7vvOESApLU5o0icVXeakfSz0LsygEnekDbxPnE5af/9FEkXJD5EoYG SEahaEtgNrR4qsyxyAGYgZlS70vkSSYJ+iT2rrwEiDlo31MzRo6Ba2FfHBSJ7lcYdPT7bbk9 AO3hlNMhNdUhoQv7M5HsnqZ6unvSHOKmReNaS9egAGdRN0/GPDWr9wroyJ65ZNQsHl9nXBqE AukZNr5oJO5vxrYiAuuTSd6UI/xFkjtkzltG3mw5ao2bBpk/V/YuePrJsnPFHG7NhizrxttB nTuOSCMo45pfHQ+XYd5K1+Cv/NzZFNWscm5htJ0HznY+oOsZvHTyGz3v91pn51dkRYN0otqr bQ4tlFFuVjArBZcapSIe6NV8C4cEiSS5AQ0EVEJxcwEIAK+nUrsUz3aP2aBjIrX3a1+C+39R nctpNIPcJjFJ/8WafRiwcEuLjbvJ/4kyM6K7pWUIQftl1P8Woxwb5nqL7zEFHh5I+hKS3haO 5pgco//V0tWBGMKinjqntpd4U4Dl299dMBZ4rRbPvmI8rr63sCENxTnHhTECyHdGFpqSzWzy 97rH68uqMpxbUeggVwYkYihZNd8xt1+lf7GWYNEO/QV8ar/qbRPG6PEfiPPHQd/sldGYavmd //o6TQLSJsvJyJDt7KxulnNT8Q2X/OdEuVQsRT5glLaSAeVAABcLAEnNgmCIGkX7TnQF8a6w gHGrZIR9ZCoKvDxAr7RP6mPeS9sAEQEAAYkDEgQYAQIACQUCVEJxcwIbAgEpCRB+FRAMzTZp scBdIAQZAQIABgUCVEJxcwAKCRC/+9JfeMeug/SlCACl7QjRnwHo/VzENWD9G2VpUOd9eRnS DZGQmPo6Mp3Wy8vL7snGFBfRseT9BevXBSkxvtOnUUV2YbyLmolAODqUGzUI8ViF339poOYN i6Ffek0E19IMQ5+CilqJJ2d5ZvRfaq70LA/Ly9jmIwwX4auvXrWl99/2wCkqnWZI+PAepkcX JRD4KY2fsvRi64/aoQmcxTiyyR7q3/52Sqd4EdMfj0niYJV0Xb9nt8G57Dp9v3Ox5JeWZKXS krFqy1qyEIypIrqcMbtXM7LSmiQ8aJRM4ZHYbvgjChJKR4PsKNQZQlMWGUJO4nVFSkrixc9R Z49uIqQK3b3ENB1QkcdMg9cxsB0Onih8zR+Wp1uDZXnz1ekto+EivLQLqvTjCCwLxxJafwKI bqhQ+hGR9jF34EFur5eWt9jJGloEPVv0GgQflQaE+rRGe+3f5ZDgRe5Y/EJVNhBhKcafcbP8 MzmLRh3UDnYDwaeguYmxuSlMdjFL96YfhRBXs8tUw6SO9jtCgBvoOIBDCxxAJjShY4KIvEpK b2hSNr8KxzelKKlSXMtB1bbHbQxiQcerAipYiChUHq1raFc3V0eOyCXK205rLtknJHhM5pfG 6taABGAMvJgm/MrVILIxvBuERj1FRgcgoXtiBmLEJSb7akcrRlqe3MoPTntSTNvNzAJmfWhd SvP0G1WDLolqvX0OtKMppI91AWVu72f1kolJg43wbaKpRJg1GMkKEI3H+jrrlTBrNl/8e20m TElPRDKzPiowmXeZqFSS1A6Azv0TJoo9as+lWF+P4zCXt40+Zhh5hdHO38EV7vFAVG3iuay6 7ToF8Uy7tgc3mdH98WQSmHcn/H5PFYk3xTP3KHB7b0FZPdFPQXBZb9+tJeZBi9gMqcjMch+Y R8dmTcQRQX14bm5nXlBF7VpSOPZMR392LY7wzAvRdhz7aeIUkdO7VelaspFk2nT7wOj1Y6uL nRxQlLkBDQRUQnHuAQgAx4dxXO6/Zun0eVYOnr5GRl76+2UrAAemVv9Yfn2PbDIbxXqLff7o yVJIkw4WdhQIIvvtu5zH24iYjmdfbg8iWpP7NqxUQRUZJEWbx2CRwkMHtOmzQiQ2tSLjKh/c HeyFH68xjeLcinR7jXMrHQK+UCEw6jqi1oeZzGvfmxarUmS0uRuffAb589AJW50kkQK9VD/9 QC2FJISSUDnRC0PawGSZDXhmvITJMdD4TjYrePYhSY4uuIV02v028TVAaYbIhxvDY0hUQE4r 8ZbGRLn52bEzaIPgl1p/adKfeOUeMReg/CkyzQpmyB1TSk8lDMxQzCYHXAzwnGi8WU9iuE1P 0wARAQABiQHzBBgBAgAJBQJUQnHuAhsMAAoJEH4VEAzNNmmxp1EOoJy0uZggJm7gZKeJ7iUp eX4eqUtqelUw6gU2daz2hE/jsxsTbC/w5piHmk1H1VWDKEM4bQBTuiJ0bfo55SWsUNN+c9hh IX+Y8LEe22izK3w7mRpvGcg+/ZRG4DEMHLP6JVsv5GMpoYwYOmHnplOzCXHvmdlW0i6SrMsB Dl9rw4AtIa6bRwWLim1lQ6EM3PWifPrWSUPrPcw4OLSwFk0CPqC4HYv/7ZnASVkR5EERFF3+ 6iaaVi5OgBd81F1TCvCX2BEyIDRZLJNvX3TOd5FEN+lIrl26xecz876SvcOb5SL5SKg9/rCB ufdPSjojkGFWGziHiFaYhbuI2E+NfWLJtd+ZvWAAV+O0d8vFFSvriy9enJ8kxJwhC0ECbSKF Y+W1eTIhMD3aeAKY90drozWEyHhENf4l/V+Ja5vOnW+gCDQkGt2Y1lJAPPSIqZKvHzGShdh8 DduC0U3xYkfbGAUvbxeepjgzp0uEnBXfPTy09JGpgWbg0w91GyfT/ujKaGd4vxG2Ei+MMNDm S1SMx7wu0evvQ5kT9NPzyq8R2GIhVSiAd2jioGuTjX6AZCFv3ToO53DliFMkVTecLptsXaes uUHgL9dKIfvpm+rNXRn9wAwGjk0X/A== Message-ID: <9516b2a1-875e-1850-ed2f-0c8e94eab980@redhat.com> Date: Fri, 22 Feb 2019 18:12:07 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190222164501.13605-1-vkuznets@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Fri, 22 Feb 2019 17:12:16 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 22/02/19 17:45, Vitaly Kuznetsov wrote: > Commit 14c07ad89f4d ("x86/kvm/mmu: introduce guest_mmu") brought one subtle > change: previously, when switching back from L2 to L1, we were resetting > MMU hooks (like mmu->get_cr3()) in kvm_init_mmu() called from > nested_vmx_load_cr3() and now we do that in nested_ept_uninit_mmu_context() > when we re-target vcpu->arch.mmu pointer. > The change itself looks logical: if nested_ept_init_mmu_context() changes > something than nested_ept_uninit_mmu_context() restores it back. There is, > however, one thing: the following call chain: > > nested_vmx_load_cr3() > kvm_mmu_new_cr3() > __kvm_mmu_new_cr3() > fast_cr3_switch() > cached_root_available() > > now happens with MMU hooks pointing to the new MMU (root MMU in our case) > while previously it was happening with the old one. cached_root_available() > tries to stash current root but it is incorrect to read current CR3 with > mmu->get_cr3(), we need to use old_mmu->get_cr3() which in case we're > switching from L2 to L1 is guest_mmu. (BTW, in shadow page tables case this > is a non-issue because we don't switch MMU). > > While we could've tried to guess that we're switching between MMUs and call > the right ->get_cr3() from cached_root_available() this seems to be overly > complicated. Instead, just stash the corresponding CR3 when setting > root_hpa and make cached_root_available() use the stashed value. > > Fixes: 14c07ad89f4d ("x86/kvm/mmu: introduce guest_mmu") > Signed-off-by: Vitaly Kuznetsov Is the bug latent until the other patch? Or are they completely separate issues? Thanks, Paolo > --- > arch/x86/include/asm/kvm_host.h | 1 + > arch/x86/kvm/mmu.c | 17 +++++++++++++---- > 2 files changed, 14 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h > index be87f71ccaa5..180373360e34 100644 > --- a/arch/x86/include/asm/kvm_host.h > +++ b/arch/x86/include/asm/kvm_host.h > @@ -398,6 +398,7 @@ struct kvm_mmu { > void (*update_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp, > u64 *spte, const void *pte); > hpa_t root_hpa; > + gpa_t root_cr3; > union kvm_mmu_role mmu_role; > u8 root_level; > u8 shadow_root_level; > diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c > index 90ba1a1755a4..f2d1d230d5b8 100644 > --- a/arch/x86/kvm/mmu.c > +++ b/arch/x86/kvm/mmu.c > @@ -3555,6 +3555,7 @@ void kvm_mmu_free_roots(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, > &invalid_list); > mmu->root_hpa = INVALID_PAGE; > } > + mmu->root_cr3 = 0; > } > > kvm_mmu_commit_zap_page(vcpu->kvm, &invalid_list); > @@ -3610,6 +3611,7 @@ static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu) > vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root); > } else > BUG(); > + vcpu->arch.mmu->root_cr3 = vcpu->arch.mmu->get_cr3(vcpu); > > return 0; > } > @@ -3618,10 +3620,11 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > { > struct kvm_mmu_page *sp; > u64 pdptr, pm_mask; > - gfn_t root_gfn; > + gfn_t root_gfn, root_cr3; > int i; > > - root_gfn = vcpu->arch.mmu->get_cr3(vcpu) >> PAGE_SHIFT; > + root_cr3 = vcpu->arch.mmu->get_cr3(vcpu); > + root_gfn = root_cr3 >> PAGE_SHIFT; > > if (mmu_check_root(vcpu, root_gfn)) > return 1; > @@ -3646,7 +3649,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > ++sp->root_count; > spin_unlock(&vcpu->kvm->mmu_lock); > vcpu->arch.mmu->root_hpa = root; > - return 0; > + goto set_root_cr3; > } > > /* > @@ -3712,6 +3715,9 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu) > vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->lm_root); > } > > +set_root_cr3: > + vcpu->arch.mmu->root_cr3 = root_cr3; > + > return 0; > } > > @@ -4163,7 +4169,7 @@ static bool cached_root_available(struct kvm_vcpu *vcpu, gpa_t new_cr3, > struct kvm_mmu_root_info root; > struct kvm_mmu *mmu = vcpu->arch.mmu; > > - root.cr3 = mmu->get_cr3(vcpu); > + root.cr3 = mmu->root_cr3; > root.hpa = mmu->root_hpa; > > for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) { > @@ -4176,6 +4182,7 @@ static bool cached_root_available(struct kvm_vcpu *vcpu, gpa_t new_cr3, > } > > mmu->root_hpa = root.hpa; > + mmu->root_cr3 = root.cr3; > > return i < KVM_MMU_NUM_PREV_ROOTS; > } > @@ -5517,11 +5524,13 @@ int kvm_mmu_create(struct kvm_vcpu *vcpu) > vcpu->arch.walk_mmu = &vcpu->arch.root_mmu; > > vcpu->arch.root_mmu.root_hpa = INVALID_PAGE; > + vcpu->arch.root_mmu.root_cr3 = 0; > vcpu->arch.root_mmu.translate_gpa = translate_gpa; > for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) > vcpu->arch.root_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID; > > vcpu->arch.guest_mmu.root_hpa = INVALID_PAGE; > + vcpu->arch.guest_mmu.root_cr3 = 0; > vcpu->arch.guest_mmu.translate_gpa = translate_gpa; > for (i = 0; i < KVM_MMU_NUM_PREV_ROOTS; i++) > vcpu->arch.guest_mmu.prev_roots[i] = KVM_MMU_ROOT_INFO_INVALID; >