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Sun, 5 Nov 2023 16:31:12 +0000 (UTC) From: Paolo Bonzini To: Paolo Bonzini , Marc Zyngier , Oliver Upton , Huacai Chen , Michael Ellerman , Anup Patel , Paul Walmsley , Palmer Dabbelt , Albert Ou , Sean Christopherson , Alexander Viro , Christian Brauner , "Matthew Wilcox (Oracle)" , Andrew Morton Cc: 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?= =?utf-8?q?=C3=BCn?= , Vlastimil Babka , Vishal Annapurve , Ackerley Tng , Maciej Szmigiero , David Hildenbrand , Quentin Perret , Michael Roth , Wang , Liam Merwick , Isaku Yamahata , "Kirill A. Shutemov" Subject: [PATCH 04/34] KVM: WARN if there are dangling MMU invalidations at VM destruction Date: Sun, 5 Nov 2023 17:30:07 +0100 Message-ID: <20231105163040.14904-5-pbonzini@redhat.com> In-Reply-To: <20231105163040.14904-1-pbonzini@redhat.com> References: <20231105163040.14904-1-pbonzini@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.11.54.6 X-Stat-Signature: 5zrzhw77hah3ntoeuzdtqyid9uzznkbe X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 7421140007 X-Rspam-User: X-HE-Tag: 1699201885-163491 X-HE-Meta: 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 9w/Je+49 4TygaDdvw+0v6orT8CTfDWINOFNp38fhNjwo84xbQUa/4u1aHjUvJO4RnQ6yFwuCRbcCk7B1LJ22hQMwrG+hJadNN1AFy5zO6u6MMhRCnCM9uwnW5rsKMir23tEmwhtatSCl0D20FMLYNBwUzeO4Fqe527hqH2L8mWn41Y7+uRy1BhsTWs9aRvva6KzKgSapMvEoN4Q1hKldrAnbkpO5RfsmTV0KIqi62EkZ4Pz5nts63ib3XZG2i8Di/Cx+a3FSGGaKrbBUohYqAYN9zkWh8ucK82ukxVViqqr6Aj2G3Pwfz5x/bowX7cF7pfg41A1uAyLnNqdDkMJkO/+QYzp4dqas0wAy+suRIoqZ0 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: From: Sean Christopherson Add an assertion that there are no in-progress MMU invalidations when a VM is being destroyed, with the exception of the scenario where KVM unregisters its MMU notifier between an .invalidate_range_start() call and the corresponding .invalidate_range_end(). KVM can't detect unpaired calls from the mmu_notifier due to the above exception waiver, but the assertion can detect KVM bugs, e.g. such as the bug that *almost* escaped initial guest_memfd development. Link: https://lore.kernel.org/all/e397d30c-c6af-e68f-d18e-b4e3739c5389@linux.intel.com Signed-off-by: Sean Christopherson Reviewed-by: Paolo Bonzini Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Message-Id: <20231027182217.3615211-5-seanjc@google.com> Signed-off-by: Paolo Bonzini --- virt/kvm/kvm_main.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 9cc57b23ec81..5422ce20dcba 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1358,9 +1358,16 @@ static void kvm_destroy_vm(struct kvm *kvm) * No threads can be waiting in kvm_swap_active_memslots() as the * last reference on KVM has been dropped, but freeing * memslots would deadlock without this manual intervention. + * + * If the count isn't unbalanced, i.e. KVM did NOT unregister its MMU + * notifier between a start() and end(), then there shouldn't be any + * in-progress invalidations. */ WARN_ON(rcuwait_active(&kvm->mn_memslots_update_rcuwait)); - kvm->mn_active_invalidate_count = 0; + if (kvm->mn_active_invalidate_count) + kvm->mn_active_invalidate_count = 0; + else + WARN_ON(kvm->mmu_invalidate_in_progress); #else kvm_flush_shadow_all(kvm); #endif