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Fri, 13 Jun 2025 15:48:12 -0700 (PDT) Date: Fri, 13 Jun 2025 15:48:10 -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> 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" 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