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AJvYcCUvmnD1MhNNtTDvmgrXgR+otEL5Tm0tW+s6SbQ4Mu2lPyXYdPFdwF4APDlObphekrgyocA=@vger.kernel.org X-Gm-Message-State: AOJu0Yz2xh5Ds3ANP05nIJIVFMIKbDjIeVORHiqDG2cElpUIzV2R1DoL L2Ucr7zHtZuwEQjznYjLRZmi4YI33AJjkENLCe1pOfnVx30DLaVVq3xqo4cDsJV0S2LxZX2Sn3S HXFJZ1w== 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: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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" 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.