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[2003:cb:c70b:b400:e20a:6d03:7ac8:f97d]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-ab384f290a9sm1081240066b.101.2025.01.23.06.15.34 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 23 Jan 2025 06:15:37 -0800 (PST) Message-ID: <12286d1d-7671-4c0f-bede-53524ed94f0e@redhat.com> Date: Thu, 23 Jan 2025 15:15:34 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 2/9] KVM: guest_memfd: Add guest_memfd support to kvm_(read|/write)_guest_page() To: Fuad Tabba Cc: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, 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, xiaoyao.li@intel.com, yilun.xu@intel.com, chao.p.peng@linux.intel.com, jarkko@kernel.org, amoorthy@google.com, dmatlack@google.com, yu.c.zhang@linux.intel.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 References: <20250122152738.1173160-1-tabba@google.com> <20250122152738.1173160-3-tabba@google.com> <82d8d3a3-6f06-4904-9d94-6f92bba89dbc@redhat.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Stat-Signature: gpcbbgjwbftwyafzudkax361qe38mnrf X-Rspamd-Queue-Id: B957BC0015 X-Rspam-User: X-Rspamd-Server: rspam06 X-HE-Tag: 1737641743-454169 X-HE-Meta: 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 9JkMjx2f 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.001168, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: >> >> One interesting question is: when would you want shared memory in >> guest_memfd and *not* provide it as part of the same memslot. >> > > My original thinking wasn't that we wouldn't _want_ to, rather that we > don't _need_ to. I mistakenly thought that it would simplify things, > but, especially after this discussion, I now realize that it makes > things more complicated instead. Right, and it's not off the table: we could always add support for this "no mmaped shared guest_memfd" memory later if there is good reason to have it. -- Cheers, David / dhildenb