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AJvYcCUBolycJyyTcgYqEeCor1J4OwpF9YkWUwJpQGMiCBfecG1xMEPN528wJcF5ETIUTk4PH9JH5gTtQtZGSbn0@vger.kernel.org X-Gm-Message-State: AOJu0YzF4rskDvXKStqM0tXNi3VOKmTWNQtlSrLoqXSI8Qrc0/o2Phf0 VXqeBnRaFKwLoAgzzoz4FQ0wgdowxn8wgT3XzD91GT8sEtMdNB0DqqU9y9EY1u+fXivlO6lqUnk hsBYuX8Usfw77SzwO102oNZg0bI0S2qg8O2tuYG+h X-Gm-Gg: ASbGncuPBAxJuimS8Bt6qHSlF6iS/al46+kyuDhCIRevAbc7p7ACZhPYW+ARbpAAonM LJY6U4XG4R0rAMIdWUozwk6mUgpONPxIJfqmbBkzQ/e9kkLctYyLnDFbIOxrQR2KHPwVK8kRw3V JspbUbNT7T5zN/x4tIjghvZUGjKUg2KEaPDYZV+yjRxJdIjV+DSTNRWMxuSOtZjWtvu2i+RnKHm g== X-Google-Smtp-Source: AGHT+IG6uFwfViV4uRKlN7dtoaYWYJ2cAvUBFCR9zSfu99Vwne4/Ojg06Ia/L5ZZcaIijmv3rovYpa5VMqmmYY4ViY8= X-Received: by 2002:a17:903:98c:b0:234:c2e7:a0e7 with SMTP id d9443c01a7336-23dd0f66398mr1276695ad.4.1751933670151; Mon, 07 Jul 2025 17:14:30 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: In-Reply-To: From: Vishal Annapurve Date: Mon, 7 Jul 2025 17:14:17 -0700 X-Gm-Features: Ac12FXz8PyaRfu4rhO-WaL1IGCmpiHbF9FfbCawryHLn0bG8xOVNVPi0PuKZNZ0 Message-ID: Subject: Re: [RFC PATCH v2 00/51] 1G page support for guest_memfd To: Sean Christopherson Cc: Yan Zhao , Xiaoyao Li , Ackerley Tng , kvm@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, linux-fsdevel@vger.kernel.org, aik@amd.com, ajones@ventanamicro.com, akpm@linux-foundation.org, amoorthy@google.com, anthony.yznaga@oracle.com, anup@brainfault.org, aou@eecs.berkeley.edu, bfoster@redhat.com, binbin.wu@linux.intel.com, brauner@kernel.org, catalin.marinas@arm.com, chao.p.peng@intel.com, chenhuacai@kernel.org, dave.hansen@intel.com, david@redhat.com, dmatlack@google.com, dwmw@amazon.co.uk, erdemaktas@google.com, fan.du@intel.com, fvdl@google.com, graf@amazon.com, haibo1.xu@intel.com, hch@infradead.org, 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, jroedel@suse.de, jthoughton@google.com, jun.miao@intel.com, kai.huang@intel.com, keirf@google.com, kent.overstreet@linux.dev, kirill.shutemov@intel.com, liam.merwick@oracle.com, maciej.wieczor-retman@intel.com, mail@maciej.szmigiero.name, maz@kernel.org, mic@digikod.net, michael.roth@amd.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, pdurrant@amazon.co.uk, peterx@redhat.com, pgonda@google.com, pvorel@suse.cz, qperret@google.com, quic_cvanscha@quicinc.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, quic_svaddagi@quicinc.com, quic_tsoni@quicinc.com, richard.weiyang@gmail.com, rick.p.edgecombe@intel.com, rientjes@google.com, roypat@amazon.co.uk, rppt@kernel.org, shuah@kernel.org, steven.price@arm.com, steven.sistare@oracle.com, suzuki.poulose@arm.com, tabba@google.com, thomas.lendacky@amd.com, usama.arif@bytedance.com, vbabka@suse.cz, viro@zeniv.linux.org.uk, vkuznets@redhat.com, wei.w.wang@intel.com, will@kernel.org, willy@infradead.org, yilun.xu@intel.com, yuzenghui@huawei.com, zhiquan1.li@intel.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, Jul 7, 2025 at 4:25=E2=80=AFPM Sean Christopherson wrote: > > On Tue, Jul 01, 2025, Vishal Annapurve wrote: > > I would be curious to understand if we need zeroing on conversion for > > Confidential VMs. If not, then the simple rule of zeroing on > > allocation only will work for all usecases. > > Unless I'm misunderstanding what your asking, pKVM very specific does NOT= want > zeroing on conversion, because one of its use cases is in-place conversio= n, e.g. > to fill a shared buffer and then convert it to private so that the buffer= can be > processed in the TEE. Yeah, that makes sense. So "just zero on allocation" (and no more zeroing during conversion) policy will work for pKVM. > > Some architectures, e.g. SNP and TDX, may effectively require zeroing on = conversion, > but that's essentially a property of the architecture, i.e. an arch/vendo= r specific > detail. Conversion operation is a unique capability supported by guest_memfd files so my intention of bringing up zeroing was to better understand the need and clarify the role of guest_memfd in handling zeroing during conversion. Not sure if I am misinterpreting you, but treating "zeroing during conversion" as the responsibility of arch/vendor specific implementation outside of guest_memfd sounds good to me.