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Shutemov" Subject: Re: [RFC PATCH v12 11/33] KVM: Introduce per-page memory attributes Message-ID: Reply-To: Yan Zhao References: <20230914015531.1419405-1-seanjc@google.com> <20230914015531.1419405-12-seanjc@google.com> Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <20230914015531.1419405-12-seanjc@google.com> X-ClientProxiedBy: SG2PR01CA0184.apcprd01.prod.exchangelabs.com (2603:1096:4:189::9) To DS7PR11MB5966.namprd11.prod.outlook.com (2603:10b6:8:71::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS7PR11MB5966:EE_|MN0PR11MB6181:EE_ X-MS-Office365-Filtering-Correlation-Id: 4301786c-6c79-4955-7eee-08dbb5b9653e X-LD-Processed: 46c98d88-e344-4ed4-8496-4ed7712e255d,ExtAddr X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0; X-Microsoft-Antispam-Message-Info: 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 dx3LvjNy mG+7WLDz2Hq1XxYZuGcjMo8ECh/evfkp0qpeTjHGl03Wbg8InT0i3Jc/h8G9gFTF/CL/5jsE+es4hq2Kw4M8yvmgTss89TWXck9PALXBbOQAG0nV/rdZ4otOLDNolshxkKHk0Wb36PmHBTsj0WkT96kXfYuUfXPMypx2uJt8STWoDOLYo3KWRQv7ZNYSQX/4u4xaDa42u2x9XCMasJ7jPS6Ebeipv/azuNQx/7GGtJG7HA0zxy9EfmFienkhNGy+Yp3rKwoMfs8EIusx+gV34qMm9/nbq7WZ/vbKaiPxEGzhgfQmNCjJfarwQxj4eOVIKdqgKzei62le71ncxbC+4yja+l0YHGGYsCISWsrwJVfHm02hJUSq6KI/rjFbJzFc+2whsgX0mdgDvp6fzb6SR1NGil6BLSlJk5BGdxnA0b1qsLaItlRwRPj2Nm3EWCNL8CTI27ftdbE3onFLNkDqZcvke3A== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, Sep 13, 2023 at 06:55:09PM -0700, Sean Christopherson wrote: > From: Chao Peng > > In confidential computing usages, whether a page is private or shared is > necessary information for KVM to perform operations like page fault > handling, page zapping etc. There are other potential use cases for > per-page memory attributes, e.g. to make memory read-only (or no-exec, > or exec-only, etc.) without having to modify memslots. > ... >> +bool kvm_range_has_memory_attributes(struct kvm *kvm, gfn_t start, gfn_t end, > + unsigned long attrs) > +{ > + XA_STATE(xas, &kvm->mem_attr_array, start); > + unsigned long index; > + bool has_attrs; > + void *entry; > + > + rcu_read_lock(); > + > + if (!attrs) { > + has_attrs = !xas_find(&xas, end); > + goto out; > + } > + > + has_attrs = true; > + for (index = start; index < end; index++) { > + do { > + entry = xas_next(&xas); > + } while (xas_retry(&xas, entry)); > + > + if (xas.xa_index != index || xa_to_value(entry) != attrs) { Should "xa_to_value(entry) != attrs" be "!(xa_to_value(entry) & attrs)" ? > + has_attrs = false; > + break; > + } > + } > + > +out: > + rcu_read_unlock(); > + return has_attrs; > +} > + ... > +/* Set @attributes for the gfn range [@start, @end). */ > +static int kvm_vm_set_mem_attributes(struct kvm *kvm, gfn_t start, gfn_t end, > + unsigned long attributes) > +{ > + struct kvm_mmu_notifier_range pre_set_range = { > + .start = start, > + .end = end, > + .handler = kvm_arch_pre_set_memory_attributes, > + .on_lock = kvm_mmu_invalidate_begin, > + .flush_on_ret = true, > + .may_block = true, > + }; > + struct kvm_mmu_notifier_range post_set_range = { > + .start = start, > + .end = end, > + .arg.attributes = attributes, > + .handler = kvm_arch_post_set_memory_attributes, > + .on_lock = kvm_mmu_invalidate_end, > + .may_block = true, > + }; > + unsigned long i; > + void *entry; > + int r = 0; > + > + entry = attributes ? xa_mk_value(attributes) : NULL; Also here, do we need to get existing attributes of a GFN first ? > + mutex_lock(&kvm->slots_lock); > + > + /* Nothing to do if the entire range as the desired attributes. */ > + if (kvm_range_has_memory_attributes(kvm, start, end, attributes)) > + goto out_unlock; > + > + /* > + * Reserve memory ahead of time to avoid having to deal with failures > + * partway through setting the new attributes. > + */ > + for (i = start; i < end; i++) { > + r = xa_reserve(&kvm->mem_attr_array, i, GFP_KERNEL_ACCOUNT); > + if (r) > + goto out_unlock; > + } > + > + kvm_handle_gfn_range(kvm, &pre_set_range); > + > + for (i = start; i < end; i++) { > + r = xa_err(xa_store(&kvm->mem_attr_array, i, entry, > + GFP_KERNEL_ACCOUNT)); > + KVM_BUG_ON(r, kvm); > + } > + > + kvm_handle_gfn_range(kvm, &post_set_range); > + > +out_unlock: > + mutex_unlock(&kvm->slots_lock); > + > + return r; > +}