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Date: Tue, 8 Mar 2022 21:29:04 +0000 From: Sean Christopherson <seanjc@...gle.com> To: Paolo Bonzini <pbonzini@...hat.com> Cc: linux-kernel@...r.kernel.org, kvm@...r.kernel.org, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, David Hildenbrand <david@...hat.com>, David Matlack <dmatlack@...gle.com>, Ben Gardon <bgardon@...gle.com>, Mingwei Zhang <mizhang@...gle.com> Subject: Re: [PATCH v4 21/30] KVM: x86/mmu: Zap invalidated roots via asynchronous worker On Sat, Mar 05, 2022, Paolo Bonzini wrote: > On 3/5/22 01:34, Sean Christopherson wrote: > > On Fri, Mar 04, 2022, Paolo Bonzini wrote: > > > On 3/4/22 17:02, Sean Christopherson wrote: > > > > On Fri, Mar 04, 2022, Paolo Bonzini wrote: > > > > > On 3/3/22 22:32, Sean Christopherson wrote: > > > > > I didn't remove the paragraph from the commit message, but I think it's > > > > > unnecessary now. The workqueue is flushed in kvm_mmu_zap_all_fast() and > > > > > kvm_mmu_uninit_tdp_mmu(), unlike the buggy patch, so it doesn't need to take > > > > > a reference to the VM. > > > > > > > > > > I think I don't even need to check kvm->users_count in the defunct root > > > > > case, as long as kvm_mmu_uninit_tdp_mmu() flushes and destroys the workqueue > > > > > before it checks that the lists are empty. > > > > > > > > Yes, that should work. IIRC, the WARN_ONs will tell us/you quite quickly if > > > > we're wrong :-) mmu_notifier_unregister() will call the "slow" kvm_mmu_zap_all() > > > > and thus ensure all non-root pages zapped, but "leaking" a worker will trigger > > > > the WARN_ON that there are no roots on the list. > > > > > > Good, for the record these are the commit messages I have: > > I'm seeing some hangs in ~50% of installation jobs, both Windows and Linux. > I have not yet tried to reproduce outside the automated tests, or to bisect, > but I'll try to push at least the first part of the series for 5.18. Out of curiosity, what was the bug? I see this got pushed to kvm/next.
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