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AJvYcCXbxQt7BDAQiqjY7OvRT9M1yHQeGgTzulyQFmILcG6sn5UsDPSXFyXzf1pK0dF8qLUfk1wZD6B2xw==@kvack.org X-Gm-Message-State: AOJu0YwirlRleY87xmMl+Q6oTMqiomf6PK5Vq7anisZ6wvRXJ3YDMqby sOGDYDm2DU1cFWEPLPrXc0KtR0xS7AID7s0hbziOVRSUrmAFWBveRmX+GD7yMYs7HPy4hrCg8Hu lJ3Mocw== X-Google-Smtp-Source: AGHT+IFYrz5Id5uH6iXof80e1fCW/jK+FUGGZzqnfiU3o4Gv59B5LgfHnd+rsdx73+Z8UQC28CXkLiecz6U= X-Received: from pjyd13.prod.google.com ([2002:a17:90a:dfcd:b0:30a:31eb:ec8e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:d60b:b0:313:283e:e87c with SMTP id 98e67ed59e1d1-313f1c77731mr27133495a91.3.1750297839512; Wed, 18 Jun 2025 18:50:39 -0700 (PDT) Date: Wed, 18 Jun 2025 18:50:37 -0700 In-Reply-To: Mime-Version: 1.0 References: <20250611133330.1514028-1-tabba@google.com> <20250611133330.1514028-9-tabba@google.com> <68501fa5dce32_2376af294d1@iweiny-mobl.notmuch> <701c8716-dd69-4bf6-9d36-4f8847f96e18@redhat.com> <3fb0e82b-f4ef-402d-a33c-0b12e8aa990c@redhat.com> Message-ID: Subject: Re: [PATCH v12 08/18] KVM: guest_memfd: Allow host to map guest_memfd pages From: Sean Christopherson To: David Hildenbrand Cc: Fuad Tabba , Ira Weiny , 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, 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, 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 Content-Type: text/plain; charset="us-ascii" X-Rspam-User: X-Rspamd-Queue-Id: B848D4000A X-Rspamd-Server: rspam10 X-Stat-Signature: 3yje87buspmt6a4eiik9sr1ufiy38u65 X-HE-Tag: 1750297840-310689 X-HE-Meta: U2FsdGVkX1+H3nKYHWbIaKG446OdvPanpFQkQ1nxf9YhzU24Sby/njU4JfrqYoD7qhyKjgivfFkVYlYPBfRjYP8YJhrbWJJNUoV36zpw9CoIK+/DMGaiugDe9WujICj1imGGAncz/iH+Dcwsepu3s1/j1ylcaHggi3G7VrkUrIV2+U0yY/Y8ldrJZdm/gFP1mc+Yp6WyeNMmmQpTulk+iivf0J4ElKBOZLTKDiiggFJHEgMHReQNmCwsKUxSav22jCbn2dfjOf6uZ3qs+wf0fsAZ0qQJfVB0NEfRXDz6BoRxszN3cStyRs5eaxzjlxRi0PeF59tu2IhSo6EFK7pPLTAvfUzCIirAQG12z1vuNd2C/yaIR0TkjoOwQY3hMnJFJZcX986ht2A2Msn/ZHTINU4HVF8IjQ0Ruk9Gfu3ObY2+vNniVOhj04U+YJraiw7ONWVsRH1tRtLiP9XmyFWagnz9rSwFZm/1WhT5ux6AjtUCXloj9ovL2gLhDXDsJK2T5zvVJ9xWxWqoZuvw1N1X0GHIWAnln+pbotGKnVBm6/suuui0NnpNnq5QtnilaQQeK79VetPeJfG/IHWx025NeGsbw69drlP2VUa0FX1GH872MWsqndYIQQQu/gioPmkzyyTSJtEwxGvUwoGzXyZIXI8ErogAVEbSEelrO4fceh8zAbq5U6Reg425Y0A7ogFxdMupG2O5gULyjHfPL53f5t7MfMGvyuRU12C3WRnTG8hytQqwX9HDB+DYX0fAjGzj59mAN6nUE5AtSrErwtv5zBvPtyC4Y8FSG6/L4ioc/48prW/YxlbqsYNwBCH6QqB78cic2S66lhaoct2cKr2SDrX+aJJ90y4vwzHogTTW44zsH3pnZrpgAeBbqUgQ83aEvO/rw6HgNG9cbTV5OjuFmRej23XsRswHBqzTvmG36pPb/8sJkxQIQPzfoV0GWe5pP/3VKP0P+bWNSxkmyEH UTmgjCv4 qf5C2QEJ7jRtjgDUqQ6EDS8/FONY0OORwr9ooiEJRAn4mWvL+7bkQshiexOI3B4YO+cfw/QZRlvLTbxisIq4wZAD2P++0/b310yL+0H8GCkjZxXAAc7q8jlWsMrDkF9/pC1if9aa0gTd3XBbV4/q1ZKRV/siKRRCLKl1JUJpQ7VRiJAYLUanBTff5UojGcl9gGGHLnGgI40JpgTFzglSeWSMU76bJ/l3jZDZtCOil8q3rEZ8I4kiqqmUhMjY9cW1yte2k7CmF4KSexPGMoTXzI/gmlAYst3gt5goZLF9DljxvsvQUbQ6hiDi8yv4tyOd3J3B8rMD1pqgfB4rV0CUR8mBqRFwBtR7KR9H8ZIujEjj8f0uE1GIa4RFvaQRxSiLI8Y25vdvgWQFKALhi9z511nvmNPUGD6pNOdZlTrwX/vZH+T46B6XdOCXqKWQOnhQjZy8ip8ejSVJkFv3Ax7bRaDAP5vSRPMIhq2xcBGFYEsFUIpRojZfQx3ft9SCszhqIvo+EXPSkZm63nOTdxtJidZTXT0hLarAe+pFnq5Uj974T4+KARX8tP0cvzat2zEhGHyHtgp4vPIWePvUGhtOXPo+EXSR2akzW6jd11X4syFSKkC6rKMPyPuwEjpwk7oHTUaWmsFQiHfGf1J8vyVVMz9yznVTsnpS7r3KTLg0kw6kTK2+v+e61IAndmATl8AqVzr6fp7nvqnlX5Ws= 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, Jun 18, 2025, Sean Christopherson wrote: > On Wed, Jun 18, 2025, David Hildenbrand wrote: > > > Ya, but that's more because guest_memfd only supports MAP_SHARED, versus KVM > > > really wanting to truly share the memory with the entire system. > > > Of course, that's also an argument to some extent against USER_MAPPABLE, because > > > that name assumes we'll never want to support MAP_PRIVATE. But letting userspace > > > MAP_PRIVATE guest_memfd would completely defeat the purpose of guest_memfd, so > > > unless I'm forgetting a wrinkle with MAP_PRIVATE vs. MAP_SHARED, that's an > > > assumption I'm a-ok making. > > > > So, first important question, are we okay with adding: > > > > "GUEST_MEMFD_FLAG_MMAP": we support the mmap() operation > > Probably stating the obvious, but yes, I am. Heh, my brain is a bit fried. I didn't realize you were asking about doing s/GUEST_MEMFD_FLAG_MMAPPABLE/GUEST_MEMFD_FLAG_MMAP until I read your other mail. Luckily, I 100% agree that GUEST_MEMFD_FLAG_MMAP is way better.