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([2001:b07:6468:f312:a0d1:fc42:c610:f977]) by smtp.gmail.com with ESMTPSA id b203sm32630286wmc.22.2020.08.17.23.31.08 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Mon, 17 Aug 2020 23:31:08 -0700 (PDT) Subject: Re: [PATCH 0/2] KVM: arm64: Fix sleeping while atomic BUG() on OOM To: Will Deacon , kvmarm@lists.cs.columbia.edu, linux-kernel@vger.kernel.org, kvm@vger.kernel.org Cc: Marc Zyngier , Suzuki K Poulose , James Morse , Thomas Bogendoerfer , Paul Mackerras , Sean Christopherson References: <20200811102725.7121-1-will@kernel.org> From: Paolo Bonzini Message-ID: Date: Tue, 18 Aug 2020 08:31:08 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.9.0 MIME-Version: 1.0 In-Reply-To: <20200811102725.7121-1-will@kernel.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/08/20 12:27, Will Deacon wrote: > Hi all, > > While stress-testing my arm64 stage-2 page-table rewrite [1], I ran into > a sleeping while atomic BUG() during OOM that I can reproduce with > mainline. > > The problem is that the arm64 page-table code periodically calls > cond_resched_lock() when unmapping the stage-2 page-tables, but in the > case of OOM, this occurs in atomic context. > > These couple of patches (based on 5.8) propagate the flags from the MMU > notifier range structure, which in turn indicate whether or not blocking > is permitted. > > Cheers, > > Will > > [1] https://android-kvm.googlesource.com/linux/+/refs/heads/topic/pgtable > > Cc: Marc Zyngier > Cc: Suzuki K Poulose > Cc: James Morse > Cc: Thomas Bogendoerfer > Cc: Paul Mackerras > Cc: Paolo Bonzini > Cc: Sean Christopherson > > --->8 > > Will Deacon (2): > KVM: Pass MMU notifier range flags to kvm_unmap_hva_range() > KVM: arm64: Only reschedule if MMU_NOTIFIER_RANGE_BLOCKABLE is not set > > arch/arm64/include/asm/kvm_host.h | 2 +- > arch/arm64/kvm/mmu.c | 19 ++++++++++++++----- > arch/mips/include/asm/kvm_host.h | 2 +- > arch/mips/kvm/mmu.c | 3 ++- > arch/powerpc/include/asm/kvm_host.h | 3 ++- > arch/powerpc/kvm/book3s.c | 3 ++- > arch/powerpc/kvm/e500_mmu_host.c | 3 ++- > arch/x86/include/asm/kvm_host.h | 3 ++- > arch/x86/kvm/mmu/mmu.c | 3 ++- > virt/kvm/kvm_main.c | 3 ++- > 10 files changed, 30 insertions(+), 14 deletions(-) > These would be okay for 5.9 too, so I plan to queue them myself before we fork for 5.10. Paolo