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Wed, 01 Nov 2023 05:51:02 -0700 (PDT) MIME-Version: 1.0 References: <20231027182217.3615211-1-seanjc@google.com> <20231027182217.3615211-5-seanjc@google.com> In-Reply-To: <20231027182217.3615211-5-seanjc@google.com> From: Fuad Tabba Date: Wed, 1 Nov 2023 12:50:26 +0000 Message-ID: Subject: Re: [PATCH v13 04/35] KVM: WARN if there are dangling MMU invalidations at VM destruction To: Sean Christopherson 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 , Jarkko Sakkinen , Anish Moorthy , David Matlack , Yu Zhang , Isaku Yamahata , =?UTF-8?B?TWlja2HDq2wgU2FsYcO8bg==?= , 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-Queue-Id: 48D311C000A X-Rspam-User: X-Stat-Signature: datigjrfsazsij1ha4syqs4wg8nhhj8x X-Rspamd-Server: rspam03 X-HE-Tag: 1698843063-27037 X-HE-Meta: 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 +RYq/vQ+ 85J6NawWMlUzTpM2LGdy1eij6f16SBKZwSkukay5kuMU4l1zA9eQrdSmxtNsHbAfEQ5wX8Eu9yGXMndTq/4eQee75PYQLU0sjrnE6tJDIAnI3FKBbxEO5ui6aRYLZmVtJZcMbod9ZwGfduu5AHdqoigK58noUVhRhe4hZSq/MdOADxMOMOkpsjdQkkko6WtPrQgm78+YFYz/bh/VS5yt1EfXpYJmHOcHC7NfQg9ihmwnkJ3OLs94P30l9x99RJNknmUbhhUaBHNA9NuXTZiLQroWyr/a16msmNasqkkNtt865Ev1ScNDbVsiyPrASvXf93PGwApimU8b7aGiEyUVeErptkEq6SmGrWz+UIKRG8CP65Dwf5yMWTMetabOjaS7m8bHxfV71G/Ty+EpuwAqSYcuoeA== 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 Fri, Oct 27, 2023 at 7:22=E2=80=AFPM Sean Christopherson wrote: > > 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 an= d > 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@li= nux.intel.com > Signed-off-by: Sean Christopherson > --- Reviewed-by: Fuad Tabba Tested-by: Fuad Tabba Cheers, /fuad > 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 1a577a25de47..4dba682586ee 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1356,9 +1356,16 @@ 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 =3D 0; > + if (kvm->mn_active_invalidate_count) > + kvm->mn_active_invalidate_count =3D 0; > + else > + WARN_ON(kvm->mmu_invalidate_in_progress); > #else > kvm_flush_shadow_all(kvm); > #endif > -- > 2.42.0.820.g83a721a137-goog >