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[2003:cb:c70b:db00:724d:8b0c:110e:3713]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-38bf32151e6sm17120330f8f.20.2025.01.22.14.10.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 22 Jan 2025 14:10:20 -0800 (PST) Message-ID: Date: Wed, 22 Jan 2025 23:10:16 +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 , kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org Cc: 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> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: E995620005 X-Rspamd-Server: rspam10 X-Stat-Signature: 4zcg7jmu89tdzp3ngnujxg8w96xt86em X-HE-Tag: 1737583824-899094 X-HE-Meta: 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 vNGHErRR 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 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 22.01.25 16:27, Fuad Tabba wrote: > Make kvm_(read|/write)_guest_page() capable of accessing guest > memory for slots that don't have a userspace address, but only if > the memory is mappable, which also indicates that it is > accessible by the host. Interesting. So far my assumption was that, for shared memory, user space would simply mmap() guest_memdd and pass it as userspace address to the same memslot that has this guest_memfd for private memory. Wouldn't that be easier in the first shot? (IOW, not require this patch with the cost of faulting the shared page into the page table on access) -- Cheers, David / dhildenb