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Date: Thu, 3 Mar 2022 18:08:47 +0000 From: Mingwei Zhang <mizhang@...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@...r.kernel.org, linux-kernel@...r.kernel.org, David Matlack <dmatlack@...gle.com>, Ben Gardon <bgardon@...gle.com> Subject: Re: [PATCH v3 08/28] KVM: x86/mmu: Batch TLB flushes from TDP MMU for MMU notifier change_spte On Sat, Feb 26, 2022, Sean Christopherson wrote: > Batch TLB flushes (with other MMUs) when handling ->change_spte() > notifications in the TDP MMU. The MMU notifier path in question doesn't > allow yielding and correcty flushes before dropping mmu_lock. nit: correctly > > Signed-off-by: Sean Christopherson <seanjc@...gle.com> > Reviewed-by: Ben Gardon <bgardon@...gle.com> Reviewed-by: Mingwei Zhang <mizhang@...gle.com> > --- > arch/x86/kvm/mmu/tdp_mmu.c | 13 ++++++------- > 1 file changed, 6 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c > index 848448b65703..634a2838e117 100644 > --- a/arch/x86/kvm/mmu/tdp_mmu.c > +++ b/arch/x86/kvm/mmu/tdp_mmu.c > @@ -1203,13 +1203,12 @@ static bool set_spte_gfn(struct kvm *kvm, struct tdp_iter *iter, > */ > bool kvm_tdp_mmu_set_spte_gfn(struct kvm *kvm, struct kvm_gfn_range *range) > { > - bool flush = kvm_tdp_mmu_handle_gfn(kvm, range, set_spte_gfn); > - > - /* FIXME: return 'flush' instead of flushing here. */ > - if (flush) > - kvm_flush_remote_tlbs_with_address(kvm, range->start, 1); > - > - return false; > + /* > + * No need to handle the remote TLB flush under RCU protection, the > + * target SPTE _must_ be a leaf SPTE, i.e. cannot result in freeing a > + * shadow page. See the WARN on pfn_changed in __handle_changed_spte(). > + */ > + return kvm_tdp_mmu_handle_gfn(kvm, range, set_spte_gfn); > } > > /* > -- > 2.35.1.574.g5d30c73bfb-goog >
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