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Wed, 21 May 2025 04:11:13 -0700 (PDT) MIME-Version: 1.0 References: <20250513163438.3942405-1-tabba@google.com> <20250513163438.3942405-14-tabba@google.com> <8d6eb79a-a68d-4116-bb42-ed18b0a0d37d@redhat.com> In-Reply-To: <8d6eb79a-a68d-4116-bb42-ed18b0a0d37d@redhat.com> From: Fuad Tabba Date: Wed, 21 May 2025 12:10:36 +0100 X-Gm-Features: AX0GCFsGsg3FxndHSZGJf7TgUxTEca7xqtxeGk7gRA7wW8yw3Stt3ibiefTaF9w Message-ID: Subject: Re: [PATCH v9 13/17] KVM: arm64: Handle guest_memfd()-backed guest page faults To: David Hildenbrand Cc: kvm@vger.kernel.org, linux-arm-msm@vger.kernel.org, linux-mm@kvack.org, 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, 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, ira.weiny@intel.com Content-Type: text/plain; charset="UTF-8" X-Stat-Signature: 1mcbyyhe6rhghb5awm9rh3k6aauzyf63 X-Rspamd-Queue-Id: B45E54000A X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1747825874-962805 X-HE-Meta: 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 cqzfIWZv J6kqhD9aifSGuxHV8k8NnGkC9VEaj/hfOLs5IjjMTbv/wc3IRayMlSKs5B2Vw2jjcYECCmlnZTVuHQDDS7WYfo05Tw0+/nKhbCv8Z34B9SSPQrdTXgmAd8B3ULSPI9BiirSYrixI8tnMRQtgVHXGQ6rGfskUEVPTxCqLOUjhkqg/ow1WcyT5xW3Bi0qYH6dVBy1cnITzVijkXyjtWkNcVBPzwGXROg91z6FvJBHfjz4D0Y/qEl0mhcgrFvN4pHAev2dTsDAs8ZQr/gHanLyohJIAwyZLIOZYb2QxK5cx0naK7CP33pbctKF51SCZ49EZDyup7NG5z6vvlGlox2yPjSlOnSntBYPE3m/3HVu117JycUZQ= 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: Hi David, On Wed, 21 May 2025 at 09:04, David Hildenbrand wrote: > > On 13.05.25 18:34, Fuad Tabba wrote: > > Add arm64 support for handling guest page faults on guest_memfd > > backed memslots. > > > > For now, the fault granule is restricted to PAGE_SIZE. > > > > Signed-off-by: Fuad Tabba > > --- > > [...] > > > + if (!is_gmem) { > > Should we add a comment somewhere, stating that we don't support VMs > with private memory, so if we have a gmem, all faults are routed through > that? I guess this is related to the other thread we had. This would handle private memory correctly. It's just that for arm64 as it is, having private memory isn't that useful. There might be a use-case where a user would create a guest_memfd-backed slot that supports private memory, and one that doesn't, which only the guest would use. I doubt that that's actually useful, but it would work and behave as expected. Cheers, /fuad > > + mmap_read_lock(current->mm); > > + vma = vma_lookup(current->mm, hva); > > + if (unlikely(!vma)) { > > + kvm_err("Failed to find VMA for hva 0x%lx\n", hva); > > + mmap_read_unlock(current->mm); > > + return -EFAULT; > > + } > > + > > + vfio_allow_any_uc = vma->vm_flags & VM_ALLOW_ANY_UNCACHED; > > + mte_allowed = kvm_vma_mte_allowed(vma); > > -- > Cheers, > > David / dhildenb >