Messages in this thread | | | Subject | Re: [PATCH 12/13] KVM: x86/mmu: Fast invalidation for TDP MMU | From | Paolo Bonzini <> | Date | Thu, 1 Apr 2021 19:02:43 +0200 |
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On 01/04/21 18:50, Ben Gardon wrote: >> This is just cosmetic, but I'd prefer to keep the call to >> kvm_tdp_mmu_invalidate_roots at the original place, so that it's clear >> in the next patch that it's two separate parts because of the different >> locking requirements. > I'm not sure exactly what you mean and I could certainly do a better > job explaining in the commit description, but it's actually quite > important that kvm_tdp_mmu_invalidate_roots at least precede > kvm_zap_obsolete_pages as kvm_zap_obsolete_pages drops the lock and > yields. If kvm_tdp_mmu_invalidate_roots doesn't go first then vCPUs > could wind up dropping their ref on an old root and then picking it up > again before the last root had a chance to drop its ref. > Explaining in the description that kvm_tdp_mmu_zap_all is being > dropped because it is no longer necessary (as opposed to being moved) > might help make that cleaner.
No, what would help is the remark you just made about kvm_zap_obsolete_pages yielding. But that doesn't matter after 13/13 though, does it? Perhaps it's easier to just combine them.
Paolo
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