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Mon, 22 Feb 2021 08:24:59 -0800 (PST) Received: from google.com ([2620:15c:f:10:655e:415b:3b95:bd58]) by smtp.gmail.com with ESMTPSA id f2sm21929378pfk.63.2021.02.22.08.24.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 22 Feb 2021 08:24:58 -0800 (PST) Date: Mon, 22 Feb 2021 08:24:51 -0800 From: Sean Christopherson To: David Stevens Subject: Re: [PATCH v4 2/2] KVM: x86/mmu: Consider the hva in mmu_notifier retry Message-ID: References: <20210222024522.1751719-1-stevensd@google.com> <20210222024522.1751719-3-stevensd@google.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20210222024522.1751719-3-stevensd@google.com> X-Mailman-Approved-At: Tue, 23 Feb 2021 09:49:10 -0500 Cc: Wanpeng Li , kvm@vger.kernel.org, David Hildenbrand , linux-mips@vger.kernel.org, Paul Mackerras , Claudio Imbrenda , kvmarm@lists.cs.columbia.edu, Janosch Frank , Marc Zyngier , Joerg Roedel , Huacai Chen , Christian Borntraeger , Aleksandar Markovic , kvm-ppc@vger.kernel.org, linux-arm-kernel@lists.infradead.org, Jim Mattson , Cornelia Huck , linux-kernel@vger.kernel.org, Paolo Bonzini , Vitaly Kuznetsov X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu On Mon, Feb 22, 2021, David Stevens wrote: > --- > v3 -> v4: > - Skip prefetch while invalidations are in progress Oof, nice catch. ... > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c > index 9ac0a727015d..f6aaac729667 100644 > --- a/arch/x86/kvm/mmu/mmu.c > +++ b/arch/x86/kvm/mmu/mmu.c > @@ -2758,6 +2758,13 @@ static void direct_pte_prefetch(struct kvm_vcpu *vcpu, u64 *sptep) > if (sp->role.level > PG_LEVEL_4K) > return; > > + /* > + * If addresses are being invalidated, skip prefetching to avoid > + * accidentally prefetching those addresses. > + */ > + if (unlikely(vcpu->kvm->mmu_notifier_count)) > + return; FNAME(pte_prefetch) needs the same check. Paolo, this brings up a good addition for the work to integrate the mmu notifier into the rest of KVM, e.g. for vmcs12 pages. Ideally, gfn_to_page_many_atomic() and __gfn_to_pfn_memslot() would WARN if mmu_notifier_count is non-zero, but that will fire all over the place until the nested code properly integrates the notifier. There are a few use cases where racing with the notifier is acceptable, e.g. reexecute_instruction(), but hopefully we can address those flows without things getting too ugly. > + > __direct_pte_prefetch(vcpu, sp, sptep); > } _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm