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AJvYcCV4gpL99zPE1Yq0TkuwyAuLGpmFwWT2fdo6xlZhMY9wUlYLZqlMqXC4pmHOAxXsMhWXleM06TD5@vger.kernel.org X-Gm-Message-State: AOJu0YwjE+25jzCHZeaH/udTtK4dJ5KVtUTTy8yxnOPjf60ZGt/t486y yolpMaBAtnrRqTLmbVlZ4Z5sasJbo/LgS2Z7nCzK0bG9ONR6ynfw5O3zTxUCf7L4FOrAXAPtBf/ rMcCvow== X-Google-Smtp-Source: AGHT+IGvJAcWikn/2GkAunTJp4wJjRX2y0XegrvA0YCLDSoXMGm33ouWPic5F/FBkAnJdnxZYF98SiNPybw= X-Received: from pjte14.prod.google.com ([2002:a17:90a:c20e:b0:33b:ca21:e3e7]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3891:b0:32e:9da9:3e60 with SMTP id 98e67ed59e1d1-33bcf9375e8mr34102450a91.36.1761327908483; Fri, 24 Oct 2025 10:45:08 -0700 (PDT) Date: Fri, 24 Oct 2025 10:45:06 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: cgroups@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <8ee16fbf254115b0fd72cc2b5c06d2ccef66eca9.1760731772.git.ackerleytng@google.com> <2457cb3b-5dde-4ca1-b75d-174b5daee28a@arm.com> Message-ID: Subject: Re: [RFC PATCH v1 07/37] KVM: Introduce KVM_SET_MEMORY_ATTRIBUTES2 From: Sean Christopherson To: Ackerley Tng Cc: Steven Price , cgroups@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, x86@kernel.org, akpm@linux-foundation.org, binbin.wu@linux.intel.com, bp@alien8.de, brauner@kernel.org, chao.p.peng@intel.com, chenhuacai@kernel.org, corbet@lwn.net, dave.hansen@intel.com, dave.hansen@linux.intel.com, david@redhat.com, dmatlack@google.com, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, haibo1.xu@intel.com, hannes@cmpxchg.org, hch@infradead.org, hpa@zytor.com, hughd@google.com, ira.weiny@intel.com, isaku.yamahata@intel.com, jack@suse.cz, james.morse@arm.com, jarkko@kernel.org, jgg@ziepe.ca, jgowans@amazon.com, jhubbard@nvidia.com, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maobibo@loongson.cn, mathieu.desnoyers@efficios.com, maz@kernel.org, mhiramat@kernel.org, mhocko@kernel.org, mic@digikod.net, michael.roth@amd.com, mingo@redhat.com, mlevitsk@redhat.com, mpe@ellerman.id.au, muchun.song@linux.dev, nikunj@amd.com, nsaenz@amazon.es, oliver.upton@linux.dev, palmer@dabbelt.com, pankaj.gupta@amd.com, paul.walmsley@sifive.com, pbonzini@redhat.com, peterx@redhat.com, pgonda@google.com, prsampat@amd.com, pvorel@suse.cz, qperret@google.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, rostedt@goodmis.org, roypat@amazon.co.uk, rppt@kernel.org, shakeel.butt@linux.dev, shuah@kernel.org, suzuki.poulose@arm.com, tabba@google.com, tglx@linutronix.de, thomas.lendacky@amd.com, vannapurve@google.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, will@kernel.org, willy@infradead.org, wyihan@google.com, xiaoyao.li@intel.com, yan.y.zhao@intel.com, yilun.xu@intel.com, yuzenghui@huawei.com Content-Type: text/plain; charset="us-ascii" On Fri, Oct 24, 2025, Ackerley Tng wrote: > Sean Christopherson writes: > > @@ -486,6 +488,7 @@ struct kvm_vm *__vm_create(struct vm_shape shape, uint32_t nr_runnable_vcpus, > > } > > guest_rng = new_guest_random_state(guest_random_seed); > > sync_global_to_guest(vm, guest_rng); > > + sync_global_to_guest(vm, kvm_has_gmem_attributes); > > I ported this [1] except for syncing this value to the guest, because I > think the guest shouldn't need to know this information, KVM selftests are about practically and testing, what information should or shouldn't be available to a test from e.g. a safety perspective is completely irrelevant. In fact, one of the biggest advantages of selftests over KUT is that the guest side can know _exactly_ what's going on in the host. See the usage in 1850e3da4b03 ("KVM: selftests: Update private_mem_conversions_test to mmap() guest_memfd") from: https://github.com/sean-jc/linux.git x86/gmem_inplace > the host should decide what to do. I think, if the guests really need to know > this, the test itself can do the syncing. Why force tests to do extra work, and potentially introduce subtle bugs due to state being stale?