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([2001:b07:6468:f312:c8dd:75d4:99ab:290a]) by smtp.gmail.com with ESMTPSA id 1sm5434627wmj.2.2021.03.05.09.53.11 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 05 Mar 2021 09:53:12 -0800 (PST) Subject: Re: [PATCH v2 00/17] KVM: x86/mmu: Lots of bug fixes To: Sean Christopherson Cc: Vitaly Kuznetsov , Wanpeng Li , Jim Mattson , Joerg Roedel , kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Ben Gardon , Brijesh Singh , Tom Lendacky References: <20210305011101.3597423-1-seanjc@google.com> From: Paolo Bonzini Message-ID: <556fe37f-02ba-5852-05b6-e1e57b275460@redhat.com> Date: Fri, 5 Mar 2021 18:53:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.7.0 MIME-Version: 1.0 In-Reply-To: <20210305011101.3597423-1-seanjc@google.com> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 05/03/21 02:10, Sean Christopherson wrote: > Fix nested NPT (nSVM) with 32-bit L1 and SME with shadow paging, which > are completely broken. Opportunistically fix theoretical bugs related to > prematurely reloading/unloading the MMU. > > If nNPT is enabled, L1 can crash the host simply by using 32-bit NPT to > trigger a null pointer dereference on pae_root. > > SME with shadow paging (including nNPT) fails to set the C-bit in the > shadow pages that don't go through standard MMU flows (PDPTPRs and the > PML4 used by nNPT to shadow legacy NPT). It also failes to account for > CR3[63:32], and thus the C-bit, being ignored outside of 64-bit mode. > > Patches 01 and 02 fix the null pointer bugs. > > Patches 03-09 fix mostly-benign related memory leaks. > > Patches 10-12 fix the SME shadow paging bugs, which are also what led me to > the nNPT null pointer bugs. > > Patches 13 and 14 fix theoretical bugs with PTP_SWITCH and INVPCID that > I found when auditing flows that touch the MMU context. > > Patches 14-17 do additional clean up to hopefully make it harder to > introduce bugs in the future. > > On the plus side, I finally understand why KVM supports shadowing 2-level > page tables with 4-level page tables... > > Based on kvm/queue, commit fe5f0041c026 ("KVM/SVM: Move vmenter.S exception > fixups out of line"). The null pointer fixes cherry-pick cleanly onto > kvm/master, haven't tried the other bug fixes (I doubt they're worth > backporting even though I tagged 'em with stable). > > v2: > - Collect a review from Ben (did not include his review of patch 03 > since the patch and its direct dependencies were changed). > - Move pae_root and lm_root allocation to a separate helper to avoid > sleeping via get_zeroed_page() while holding mmu_lock. > - Add a patch to grab 'mmu' in a local variable. > - Remove the BUILD_BUG_ON() in make_mmu_pages_available() since the > final check wouldn't actually guarnatee 4 pages were "available". > Instead, add a comment about the limit being soft. > > v1: > - https://lkml.kernel.org/r/20210302184540.2829328-1-seanjc@google.com > > Sean Christopherson (17): > KVM: nSVM: Set the shadow root level to the TDP level for nested NPT > KVM: x86/mmu: Alloc page for PDPTEs when shadowing 32-bit NPT with > 64-bit > KVM: x86/mmu: Capture 'mmu' in a local variable when allocating roots > KVM: x86/mmu: Allocate the lm_root before allocating PAE roots > KVM: x86/mmu: Allocate pae_root and lm_root pages in dedicated helper > KVM: x86/mmu: Ensure MMU pages are available when allocating roots > KVM: x86/mmu: Check PDPTRs before allocating PAE roots > KVM: x86/mmu: Fix and unconditionally enable WARNs to detect PAE leaks > KVM: x86/mmu: Use '0' as the one and only value for an invalid PAE > root > KVM: x86/mmu: Set the C-bit in the PDPTRs and LM pseudo-PDPTRs > KVM: x86/mmu: Mark the PAE roots as decrypted for shadow paging > KVM: SVM: Don't strip the C-bit from CR2 on #PF interception > KVM: nVMX: Defer the MMU reload to the normal path on an EPTP switch > KVM: x86: Defer the MMU unload to the normal path on an global INVPCID > KVM: x86/mmu: Unexport MMU load/unload functions > KVM: x86/mmu: Sync roots after MMU load iff load as successful > KVM: x86/mmu: WARN on NULL pae_root or lm_root, or bad shadow root > level > > arch/x86/include/asm/kvm_host.h | 3 - > arch/x86/kvm/mmu.h | 4 + > arch/x86/kvm/mmu/mmu.c | 273 ++++++++++++++++++++------------ > arch/x86/kvm/mmu/tdp_mmu.c | 23 +-- > arch/x86/kvm/svm/svm.c | 9 +- > arch/x86/kvm/vmx/nested.c | 9 +- > arch/x86/kvm/x86.c | 2 +- > 7 files changed, 192 insertions(+), 131 deletions(-) > Queued all except 9 and 11, thanks. Paolo