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Wed, 16 Jul 2025 04:00:17 -0700 (PDT) MIME-Version: 1.0 References: <20250715093350.2584932-1-tabba@google.com> <20250715093350.2584932-10-tabba@google.com> In-Reply-To: From: Fuad Tabba Date: Wed, 16 Jul 2025 11:59:39 +0100 X-Gm-Features: Ac12FXx9zd9JVkXqY3lez4L9ptxfAF4QCJ83KzlvcvcQhQV6SV5GBIjlcQUn8Vo Message-ID: Subject: Re: [PATCH v14 09/21] KVM: guest_memfd: Track guest_memfd mmap support in memslot To: David Hildenbrand Cc: Xiaoyao Li , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, kvmarm@lists.linux.dev, pbonzini@redhat.com, chenhuacai@kernel.org, mpe@ellerman.id.au, anup@brainfault.org, paul.walmsley@sifive.com, palmer@dabbelt.com, aou@eecs.berkeley.edu, seanjc@google.com, viro@zeniv.linux.org.uk, brauner@kernel.org, willy@infradead.org, akpm@linux-foundation.org, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, isaku.yamahata@intel.com, mic@digikod.net, vbabka@suse.cz, vannapurve@google.com, ackerleytng@google.com, mail@maciej.szmigiero.name, michael.roth@amd.com, wei.w.wang@intel.com, liam.merwick@oracle.com, isaku.yamahata@gmail.com, kirill.shutemov@linux.intel.com, suzuki.poulose@arm.com, steven.price@arm.com, quic_eberman@quicinc.com, quic_mnalajal@quicinc.com, quic_tsoni@quicinc.com, quic_svaddagi@quicinc.com, quic_cvanscha@quicinc.com, quic_pderrin@quicinc.com, quic_pheragu@quicinc.com, catalin.marinas@arm.com, james.morse@arm.com, yuzenghui@huawei.com, oliver.upton@linux.dev, maz@kernel.org, will@kernel.org, qperret@google.com, keirf@google.com, roypat@amazon.co.uk, shuah@kernel.org, hch@infradead.org, jgg@nvidia.com, rientjes@google.com, jhubbard@nvidia.com, fvdl@google.com, hughd@google.com, jthoughton@google.com, peterx@redhat.com, pankaj.gupta@amd.com, ira.weiny@intel.com Content-Type: text/plain; charset="UTF-8" X-Rspamd-Queue-Id: AC2DD1C0011 X-Rspam-User: X-Rspamd-Server: rspam09 X-Stat-Signature: ot7yh8regdhqgazcmxbr7j6rx4wzkun8 X-HE-Tag: 1752663619-457360 X-HE-Meta: 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 VDCWaHkc 8lrbgbifi68sKbkZXuyUv+zgTvcrxpW0wi/qvDSf2g3K20Nh1OilytJJHBUpVQbAwC/SCmQxDKCpdxX1FF2aDSq5BzRMAwZHFIbiT3aqY5GgMrxZbw4HoI/iAqwDz55pVarr0SHtasjXQgNEiAFm5rR42dyHbh7pTPLd22n2hzVfNqn8mwWZF7Gvk17/OsLtkk/8ak9Vx75iYrx02LBPadFa5g9NYAS+Mc1N1SuGhUp5TVDt6E05P64ZwZWWziRzvM4pez0TtD0Et4ycz9DG/75q2Y0xDXDTEkRXVm6f7Cz+ZSfygCpAEoh0ewzeqyVrQ1yztwom1ZiySzTn8dxXi6hmV/lsB7kl4xNb0joSg2pvpnOo= 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: List-Subscribe: List-Unsubscribe: On Wed, 16 Jul 2025 at 11:31, David Hildenbrand wrote: > > On 16.07.25 10:21, Fuad Tabba wrote: > > Hi Xiaoyao, > > > > On Wed, 16 Jul 2025 at 07:11, Xiaoyao Li wrote: > >> > >> On 7/15/2025 5:33 PM, Fuad Tabba wrote: > >>> Add a new internal flag, KVM_MEMSLOT_GMEM_ONLY, to the top half of > >>> memslot->flags. This flag tracks when a guest_memfd-backed memory slot > >>> supports host userspace mmap operations. It's strictly for KVM's > >>> internal use. > >> > >> I would expect some clarification of why naming it with > >> KVM_MEMSLOT_GMEM_ONLY, not something like KVM_MEMSLOT_GMEM_MMAP_ENABLED > >> > >> There was a patch to check the userspace_addr of the memslot refers to > >> the same memory as guest memfd[1], but that patch was dropped. Without > >> the background that when guest memfd is mmapable, userspace doesn't need > >> to provide separate memory via userspace_addr, it's hard to understand > >> and accept the name of GMEM_ONLY. > > > > The commit message could have clarified this a bit more. Regarding the > > rationale for the naming, there have been various threads and live > > discussions in the biweekly guest_memfd meeting . Instead of rehashing > > the discussion here, I can refer you to a couple [1, 2]. > > Maybe clarify here: > > "Add a new internal flag, KVM_MEMSLOT_GMEM_ONLY, to the top half of > memslot->flags. This flag tracks when a guest_memfd-backed memory slot > supports host userspace mmap operations, which implies that all memory, > not just private memory for CoCo VMs, is consumed through guest_memfd: > "gmem only" > > And add a pointer to the list discussion. Ack. Thanks, /fuad > -- > Cheers, > > David / dhildenb >