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AJvYcCVfOrpNAeTpw1XBMBBT9h7EcN/m8Mbe22jvIyko4aAFmxr2L42FBoyusCrX1Hzp8mxMtS5nDrnvpQ==@kvack.org X-Gm-Message-State: AOJu0YyIkzaU1rCXUwB/FcO5jUVe7KPoSLtEpTxOSB1W8X9+7Ubp6MpM 8Mge0rjwcA2AVWU2+aEcMdyD3DFkbzJez8+mXetOHH56FE3WqLAMQV51lEPT2uMXoknXlYLuUN6 t5TLT4A== X-Google-Smtp-Source: AGHT+IFmVbuER09bqe0w/t1NnKGFZRyDNJUVfxGfFpjqY6vikPqb0P4dso4PSiLkCEX/Cq6o353w4bjW7uU= X-Received: from pjbdy14.prod.google.com ([2002:a17:90b:6ce:b0:313:274d:3007]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90a:e7c6:b0:312:b4a:6342 with SMTP id 98e67ed59e1d1-313f1dd5483mr2147790a91.33.1749854892347; Fri, 13 Jun 2025 15:48:12 -0700 (PDT) Date: Fri, 13 Jun 2025 15:48:10 -0700 In-Reply-To: Mime-Version: 1.0 References: <20250611133330.1514028-1-tabba@google.com> <20250611133330.1514028-9-tabba@google.com> Message-ID: Subject: Re: [PATCH v12 08/18] KVM: guest_memfd: Allow host to map guest_memfd pages From: Sean Christopherson To: Fuad Tabba Cc: 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, david@redhat.com, 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="us-ascii" X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: C8472C0002 X-Stat-Signature: zz8qqf3m46dyied4ot33w873qqb15jp9 X-Rspam-User: X-HE-Tag: 1749854893-549438 X-HE-Meta: U2FsdGVkX18z15Fw3fvNbq5ww2LXqQRwXoA3B/401LkZsE50IoHN3aCPfSszgMDtGnad40xKz55gdKQvyqCXHW9CAWVgmvR5YdWWUObawRc1Je4BVm5Z8q6Y2+nX/sFQupvjyf7qyWeKZ+GtkwnVlFY8muTjJlDkXVQWtxBJr4Io6ltLGIu5CN/B4pF+C4+MmgZgkENQew/lR9k+3qWFvPVbkqTp8pj2qRAXpDh+vYrFEUAmxFC8mH4GVHYWR56E8pOdo5FBuVFXDcrQpBbCtj1jndNsTuDk/mlkSZc6rT28CdJ+Tbc+snsDeEKPKb0j/R/4hptWGfU0HA0cErDewzCOw4+mfpw8zvEOWGGEd9Z1tNiMMqK7Cxfm8hc/HbsAhjHIPco2daP3dHZXykhatpMucliJ7eXEZAdxGEnajvsV59uM2nct4wqzHvh3XA5vKxsBgyIMC5io2RiB7euePKx2YyxrNkTTw7h+zeFuQe15EjQvjKr7ru/ZCiSf3jOf2kAbFWrHc13jfDG5ROh0xH/GSxNRKbRUiUSx/roYTDTgKSNwYrXhYmdIxVeIsg30vxvhNlkCkJ7KF6bo25aZSEI36yhSIZJMKruZlIsnVpLe4X+etg4hU34boFCfMuW4dGdbXrWVOV7C+gIqIjlZivOSXkuDP0dT1FeWpnQ9AAyywkchSyTz1dApLkYezL8qam4e7v29JFQZ1513bod8PfUry/A/D6Su2cALO861qmY2r3yuYnGdWnLW7tMsRQIwxomrQFBh4TSPpN6luXHEvscoB4LUSIqKr4CI36dU0tWg+QrO0+Qr60O8kVgqa+IbgX7tpXbS6G2c/mmBpMcYu0IdFeQUW53UNfvWHF6tKodPnnUZ3pyB+mXGD/ZGabXA+jbTK4Uj+Vj7osG4Rs1kNEV8hF1gBOuEEKmzafmdiMOSA74cxKp9I6gEG0wE86TItNR1cHlqhObbYBNN37H 70LvsvpZ 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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 Fri, Jun 13, 2025, Sean Christopherson wrote: > On Wed, Jun 11, 2025, Fuad Tabba wrote: ... > > +static vm_fault_t kvm_gmem_fault_shared(struct vm_fault *vmf) > > And to my point about "shared", this is also very confusing, because there are > zero checks in here about shared vs. private. Heh, and amusingly (to me at least), I was the one that suggested this name[*]: : > static vm_fault_t kvm_gmem_fault(struct vm_fault *vmf) : : This should be something like kvm_gmem_fault_shared() make it abundantly clear : what's being done. Because it too me a few looks to realize this is faulting : memory into host userspace, not into the guest. Though I don't think my two statements are contradictory. A bare kvm_gmem_fault() is confusing because it's ambigous. kvm_gmem_fault_shared() is confusing because "shared" is (IMO) bad terminology. E.g. to me, this is much more obvious: static vm_fault_t kvm_gmem_fault_user(struct vm_fault *vmf) or even static vm_fault_t kvm_gmem_fault_user_mapping(struct vm_fault *vmf) if we're worried about "user" getting confused with supervisor vs. user in the guest. [*] https://lore.kernel.org/all/Z-3UGmcCwJtaP-yF@google.com