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b=k64qKfJ6zNJDhsnuWxR0fgqX3BVaqQwvdZElR/klQAEoCxi1g56cxeHTAZN0/wswK Pq+3GThmFMau+x8U6BogKChu5yqp5BwT3RbxGdJVY+yxVsA/3n3361XvguUQYtAzo0 CwsxkbStJHs9RAUy1BQLHDF5j08YA23EQWtialVtSTBmcZtV4ZgvbsnBJMyvgGhChp CJH00Qs5o00iwlgrtxYWMVa2jp4VjDFoGjgtjzcCsiVePDp+01FqKPujeYxhNnJ5cJ L4zaOZ7N9WkPfF3VfgjAaCkkSQpngOXjnWintiz60FKc8w0raVBwqKL8kvbukYzLFm Bt1jthD93yq4g== Date: Fri, 15 Aug 2025 12:12:10 +0300 From: Mike Rapoport To: Jason Gunthorpe Cc: Pasha Tatashin , pratyush@kernel.org, jasonmiu@google.com, graf@amazon.com, changyuanl@google.com, dmatlack@google.com, rientjes@google.com, corbet@lwn.net, rdunlap@infradead.org, ilpo.jarvinen@linux.intel.com, kanie@linux.alibaba.com, ojeda@kernel.org, aliceryhl@google.com, masahiroy@kernel.org, akpm@linux-foundation.org, tj@kernel.org, yoann.congal@smile.fr, mmaurer@google.com, roman.gushchin@linux.dev, chenridong@huawei.com, axboe@kernel.dk, mark.rutland@arm.com, jannh@google.com, vincent.guittot@linaro.org, hannes@cmpxchg.org, dan.j.williams@intel.com, david@redhat.com, joel.granados@kernel.org, rostedt@goodmis.org, anna.schumaker@oracle.com, song@kernel.org, zhangguopeng@kylinos.cn, linux@weissschuh.net, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, gregkh@linuxfoundation.org, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, rafael@kernel.org, dakr@kernel.org, bartosz.golaszewski@linaro.org, cw00.choi@samsung.com, myungjoo.ham@samsung.com, yesanishhere@gmail.com, Jonathan.Cameron@huawei.com, quic_zijuhu@quicinc.com, aleksander.lobakin@intel.com, ira.weiny@intel.com, andriy.shevchenko@linux.intel.com, leon@kernel.org, lukas@wunner.de, bhelgaas@google.com, wagi@kernel.org, djeffery@redhat.com, stuart.w.hayes@gmail.com, ptyadav@amazon.de, lennart@poettering.net, brauner@kernel.org, linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, saeedm@nvidia.com, ajayachandra@nvidia.com, parav@nvidia.com, leonro@nvidia.com, witu@nvidia.com Subject: Re: [PATCH v3 07/30] kho: add interfaces to unpreserve folios and physical memory ranges Message-ID: References: <20250807014442.3829950-1-pasha.tatashin@soleen.com> <20250807014442.3829950-8-pasha.tatashin@soleen.com> <20250814132233.GB802098@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250814132233.GB802098@nvidia.com> X-Stat-Signature: zdhbwpamfddk99b5wmbxr1mefxnpo3cd X-Rspam-User: X-Rspamd-Queue-Id: BC4B12000C X-Rspamd-Server: rspam05 X-HE-Tag: 1755249155-336238 X-HE-Meta: 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 fMtjC4ZV i/LoS0DxoHk7odkvdBVw465t8sds5PVQGkP8eYOaQ1E5NNWiOlNL9IlAwn/3d2d8FWc1B2p7ITXhSkQMm8GNgPn+DZ4sj2fjWX9rdOWVpyHWGDgKB/LGd85zRFBybGPmD5T0fgcHRo4TdCkfIlDdThDGqW5YDued8VyAuzetxGIQxyqg+8C45p3Tv5w2fXvlpU36m0QygUEoALm7DZ2YKgx37rzajuaoLNOOhjbZGlBG4MiA9AF5RKeY0zQb4jl3Q4v22/kYxAmBrJAdVa8yJIq8vux62YGS2prMA5VQOqoGOFWMve7U2sa4DRTzZETc1xUR7VuQ6Fd1FaJc= 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 Thu, Aug 14, 2025 at 10:22:33AM -0300, Jason Gunthorpe wrote: > On Thu, Aug 07, 2025 at 01:44:13AM +0000, Pasha Tatashin wrote: > > +int kho_unpreserve_phys(phys_addr_t phys, size_t size) > > +{ > > Why are we adding phys apis? Didn't we talk about this before and > agree not to expose these? > > The places using it are goofy: > > +static int luo_fdt_setup(void) > +{ > + fdt_out = (void *)__get_free_pages(GFP_KERNEL | __GFP_ZERO, > + get_order(LUO_FDT_SIZE)); > > + ret = kho_preserve_phys(__pa(fdt_out), LUO_FDT_SIZE); > > + WARN_ON_ONCE(kho_unpreserve_phys(__pa(fdt_out), LUO_FDT_SIZE)); > > It literally allocated a page and then for some reason switches to > phys with an open coded __pa?? > > This is ugly, if you want a helper to match __get_free_pages() then > make one that works on void * directly. You can get the order of the > void * directly from the struct page IIRC when using GFP_COMP. > > Which is perhaps another comment, if this __get_free_pages() is going > to be a common pattern (and I guess it will be) then the API should be > streamlined alot more: > > void *kho_alloc_preserved_memory(gfp, size); > void kho_free_preserved_memory(void *); This looks backwards to me. KHO should not deal with memory allocation, it's responsibility to preserve/restore memory objects it supports. For __get_free_pages() the natural KHO API is kho_(un)preserve_pages(). With struct page/mesdesc we always have page_to_ from one side and page_to_pfn from the other side. Then folio and phys/virt APIS just become a thin wrappers around the _page APIs. And down the road we can add slab and maybe vmalloc. Once folio won't overlap struct page, we'll have a hard time with only kho_preserve_folio() for memory that's not actually folio (i.e. anon and page cache) > Which can wrapper the get_free_pages and the preserve logic and gives > a nice path to possibly someday supporting non-PAGE_SIZE allocations. > > Jason > -- Sincerely yours, Mike.