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AJvYcCUCVw/VUywqBx1NeShWXeIkoAJnYGf2EvAbRnvLZSiMWd88L4HSHj+uY3ScM9oFFvSCgd7SbuxxxQ==@kvack.org X-Gm-Message-State: AOJu0Yx7BSyVp/ZZQ5DOoeIYgz0uVoOLsPlKjnTGSgdBNoYo66j4ZSm+ spdV7Tme+tHPrEWF14kfmhT0j/N2SliDJSH667JwP6cPmNLFryP++ki5U/pu5MGJz2SuAEkKSUA A8xqlvrf4oizkIpJd8uhWeOvang== X-Google-Smtp-Source: AGHT+IEW234xG8sWokLR9Rty6k1AIBgtp49T5P85K9mc9H7ZjXy7xEQDhgc08MioADyUz2CbmUlZakt/hY882gqV/g== X-Received: from plsh2.prod.google.com ([2002:a17:902:b942:b0:234:f137:75cf]) (user=ackerleytng job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:dad0:b0:234:c5c1:9b73 with SMTP id d9443c01a7336-23601ec356fmr1418295ad.36.1749143754410; Thu, 05 Jun 2025 10:15:54 -0700 (PDT) Date: Thu, 05 Jun 2025 10:15:53 -0700 In-Reply-To: <85ae7dc691c86a1ae78d56d413a1b13b444b57cd.camel@intel.com> Mime-Version: 1.0 References: <7753dc66229663fecea2498cf442a768cb7191ba.1747264138.git.ackerleytng@google.com> <85ae7dc691c86a1ae78d56d413a1b13b444b57cd.camel@intel.com> Message-ID: Subject: Re: [RFC PATCH v2 38/51] KVM: guest_memfd: Split allocator pages for guest_memfd use From: Ackerley Tng To: "Edgecombe, Rick P" , "kvm@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "x86@kernel.org" Cc: "palmer@dabbelt.com" , "pvorel@suse.cz" , "catalin.marinas@arm.com" , "Miao, Jun" , "Shutemov, Kirill" , "pdurrant@amazon.co.uk" , "steven.price@arm.com" , "peterx@redhat.com" , "vbabka@suse.cz" , "jack@suse.cz" , "amoorthy@google.com" , "maz@kernel.org" , "keirf@google.com" , "vkuznets@redhat.com" , "quic_eberman@quicinc.com" , "mail@maciej.szmigiero.name" , "hughd@google.com" , "anthony.yznaga@oracle.com" , "Wang, Wei W" , "Du, Fan" , "Wieczor-Retman, Maciej" , "quic_svaddagi@quicinc.com" , "Hansen, Dave" , "ajones@ventanamicro.com" , "paul.walmsley@sifive.com" , "nsaenz@amazon.es" , "aik@amd.com" , "usama.arif@bytedance.com" , "quic_mnalajal@quicinc.com" , "fvdl@google.com" , "rppt@kernel.org" , "quic_cvanscha@quicinc.com" , "bfoster@redhat.com" , "willy@infradead.org" , "anup@brainfault.org" , "thomas.lendacky@amd.com" , "tabba@google.com" , "mic@digikod.net" , "oliver.upton@linux.dev" , "akpm@linux-foundation.org" , "Zhao, Yan Y" , "binbin.wu@linux.intel.com" , "muchun.song@linux.dev" , "Li, Zhiquan1" , "rientjes@google.com" , "mpe@ellerman.id.au" , "Aktas, Erdem" , "david@redhat.com" , "jgg@ziepe.ca" , "Annapurve, Vishal" , "Xu, Haibo1" , "jhubbard@nvidia.com" , "Yamahata, Isaku" , "jthoughton@google.com" , "will@kernel.org" , "steven.sistare@oracle.com" , "jarkko@kernel.org" , "quic_pheragu@quicinc.com" , "chenhuacai@kernel.org" , "Huang, Kai" , "shuah@kernel.org" , "dwmw@amazon.co.uk" , "pankaj.gupta@amd.com" , "Peng, Chao P" , "nikunj@amd.com" , "Graf, Alexander" , "viro@zeniv.linux.org.uk" , "pbonzini@redhat.com" , "yuzenghui@huawei.com" , "jroedel@suse.de" , "suzuki.poulose@arm.com" , "jgowans@amazon.com" , "Xu, Yilun" , "liam.merwick@oracle.com" , "michael.roth@amd.com" , "quic_tsoni@quicinc.com" , "richard.weiyang@gmail.com" , "Weiny, Ira" , "aou@eecs.berkeley.edu" , "Li, Xiaoyao" , "qperret@google.com" , "kent.overstreet@linux.dev" , "dmatlack@google.com" , "james.morse@arm.com" , "brauner@kernel.org" , "pgonda@google.com" , "quic_pderrin@quicinc.com" , "hch@infradead.org" , "roypat@amazon.co.uk" , "seanjc@google.com" Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: D684714000C X-Stat-Signature: hwws6qdehy83uppub7i4e5e96jj3b3qi X-Rspam-User: X-HE-Tag: 1749143755-359770 X-HE-Meta: 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 Ze8O+OJC 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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: "Edgecombe, Rick P" writes: > On Wed, 2025-05-14 at 16:42 -0700, Ackerley Tng wrote: >> + >> +static pgoff_t kvm_gmem_compute_invalidate_bound(struct inode *inode, >> + pgoff_t bound, bool start) >> +{ >> + size_t nr_pages; >> + void *priv; >> + >> + if (!kvm_gmem_has_custom_allocator(inode)) > > General comment - It's a bit unfortunate how kvm_gmem_has_custom_allocator() is > checked all over the place across this series. There are only two allocators > after this, right? So one is implemented with callbacks presumably designed to > fit other allocators, and one has special case logic in guest_memfd.c. > > Did you consider designing struct guestmem_allocator_operations so that it could > encapsulate the special logic for both the existing and new > allocators? I did, yes. I believe it is definitely possible to make standard 4K pages become another allocator too. I would love to clean this up. Not sure if that will be a new series after this one, or part of this one though. > If it > didn't work well, could we expect that a next allocator would actually fit > struct guestmem_allocator_operations? > This was definitely designed to support allocators beyond guestmem_hugetlb, though I won't promise that it will be a perfect fit for future allocators. This is internal to the kernel and this interface can be updated for future allocators though. >> + return bound; >> + >> + priv = kvm_gmem_allocator_private(inode); >> + nr_pages = kvm_gmem_allocator_ops(inode)->nr_pages_in_folio(priv); >> + >> + if (start) >> + return round_down(bound, nr_pages); >> + else >> + return round_up(bound, nr_pages); >> +} >> + >> +static pgoff_t kvm_gmem_compute_invalidate_start(struct inode *inode, >> + pgoff_t bound) >> +{ >> + return kvm_gmem_compute_invalidate_bound(inode, bound, true); >> +} >> + >> +static pgoff_t kvm_gmem_compute_invalidate_end(struct inode *inode, >> + pgoff_t bound) >> +{ >> + return kvm_gmem_compute_invalidate_bound(inode, bound, false); >> +} >> +