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Date: Wed, 2 Mar 2022 10:33:22 -0800 From: David Matlack <dmatlack@...gle.com> To: Sean Christopherson <seanjc@...gle.com> Cc: Paolo Bonzini <pbonzini@...hat.com>, Christian Borntraeger <borntraeger@...ux.ibm.com>, Janosch Frank <frankja@...ux.ibm.com>, Claudio Imbrenda <imbrenda@...ux.ibm.com>, 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>, kvm list <kvm@...r.kernel.org>, LKML <linux-kernel@...r.kernel.org>, Ben Gardon <bgardon@...gle.com>, Mingwei Zhang <mizhang@...gle.com> Subject: Re: [PATCH v3 22/28] KVM: x86/mmu: Zap defunct roots via asynchronous worker On Wed, Mar 2, 2022 at 9:35 AM Sean Christopherson <seanjc@...gle.com> wrote: > > On Wed, Mar 02, 2022, Paolo Bonzini wrote: > > However, I think we now need a module_get/module_put when creating/destroying > > a VM; the workers can outlive kvm_vm_release and therefore any reference > > automatically taken by VFS's fops_get/fops_put. > > Haven't read the rest of the patch, but this caught my eye. We _already_ need > to handle this scenario. As you noted, any worker, i.e. anything that takes a > reference via kvm_get_kvm() without any additional guarantee that the module can't > be unloaded is suspect. x86 is mostly fine, though kvm_setup_async_pf() is likely > affected, and other architectures seem to have bugs. > > Google has an internal patch that addresses this. I believe David is going to post > the fix... David? This was towards the back of my queue but I can bump it to the front. I'll have the patches out this week.
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