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[35.247.111.240]) by smtp.gmail.com with ESMTPSA id 130sm13473105pfy.75.2021.05.11.11.57.59 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 11 May 2021 11:57:59 -0700 (PDT) Date: Tue, 11 May 2021 18:57:55 +0000 From: Sean Christopherson To: Ben Gardon Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Paolo Bonzini , Peter Xu , Peter Shier , Yulei Zhang , Wanpeng Li , Xiao Guangrong , Kai Huang , Keqian Zhu , David Hildenbrand Subject: Re: [PATCH v4 7/7] KVM: x86/mmu: Lazily allocate memslot rmaps Message-ID: References: <20210511171610.170160-1-bgardon@google.com> <20210511171610.170160-8-bgardon@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210511171610.170160-8-bgardon@google.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Tue, May 11, 2021, Ben Gardon wrote: > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > @@ -10935,6 +10937,46 @@ static int memslot_rmap_alloc(struct kvm_memory_slot *slot, > return 0; > } > > +int alloc_all_memslots_rmaps(struct kvm *kvm) > +{ > + struct kvm_memslots *slots; > + struct kvm_memory_slot *slot; > + int r = 0; No need to initialize r. And then it makes sense to put i and r on the same line. > + int i; > + > + /* > + * Check memslots_have_rmaps early before acquiring the > + * slots_arch_lock below. > + */ > + if (smp_load_acquire(&kvm->arch.memslots_have_rmaps)) > + return 0; > + > + mutex_lock(&kvm->slots_arch_lock); > + > + /* > + * Read memslots_have_rmaps again, under the slots arch lock, > + * before allocating the rmaps > + */ > + if (smp_load_acquire(&kvm->arch.memslots_have_rmaps)) > + return 0; This fails to drop slots_arch_lock. > + > + for (i = 0; i < KVM_ADDRESS_SPACE_NUM; i++) { > + slots = __kvm_memslots(kvm, i); > + kvm_for_each_memslot(slot, slots) { > + r = memslot_rmap_alloc(slot, slot->npages); > + if (r) { > + mutex_unlock(&kvm->slots_arch_lock); > + return r; > + } > + } > + } > + > + /* Write rmap pointers before memslots_have_rmaps */ > + smp_store_release(&kvm->arch.memslots_have_rmaps, true); > + mutex_unlock(&kvm->slots_arch_lock); > + return 0; > +} > + > static int kvm_alloc_memslot_metadata(struct kvm *kvm, > struct kvm_memory_slot *slot, > unsigned long npages) > @@ -10949,7 +10991,8 @@ static int kvm_alloc_memslot_metadata(struct kvm *kvm, > */ > memset(&slot->arch, 0, sizeof(slot->arch)); > > - if (kvm->arch.memslots_have_rmaps) { > + /* Read memslots_have_rmaps before allocating the rmaps */ > + if (smp_load_acquire(&kvm->arch.memslots_have_rmaps)) { > r = memslot_rmap_alloc(slot, npages); > if (r) > return r; > -- > 2.31.1.607.g51e8a6a459-goog >