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b=Q4AjXU5UbkAQx5aYar7PCRjCmarMZeYXZZkrMlCatQoWK5Vt4UvNZUDT6N/8RNsTZ 7o5Uxs8c15urYeBLkON6Vo+a/MWPcWMcSWDzJDC7U/kxmVCl4X3jmNI9XSk2Lypjuj Q5b9Qy1JR/Y+stStQg60BmTHSgU4Ma1/0fWEyqpudzP/0aUueElJ4ot+DcUUMTbuYr 9C09LODiWWoP6DYgnYWcFcVBxLrb2hOz3xJiCc9Ffrxdf7OQs5rJ0TAY0gOfwc295v P9J6rYku7UtdVF/dK6zoP0E9eWJm0EkggPLgNL1NqZ/b3BX8aJ/V4x18OQn4+KJYqA KXKzGSk4uhW/w== Date: Wed, 26 Mar 2025 08:07:19 -0400 From: Mike Rapoport To: Jason Gunthorpe Cc: Changyuan Lyu , linux-kernel@vger.kernel.org, graf@amazon.com, akpm@linux-foundation.org, luto@kernel.org, anthony.yznaga@oracle.com, arnd@arndb.de, ashish.kalra@amd.com, benh@kernel.crashing.org, bp@alien8.de, catalin.marinas@arm.com, dave.hansen@linux.intel.com, dwmw2@infradead.org, ebiederm@xmission.com, mingo@redhat.com, jgowans@amazon.com, corbet@lwn.net, krzk@kernel.org, mark.rutland@arm.com, pbonzini@redhat.com, pasha.tatashin@soleen.com, hpa@zytor.com, peterz@infradead.org, ptyadav@amazon.de, robh+dt@kernel.org, robh@kernel.org, saravanak@google.com, skinsburskii@linux.microsoft.com, rostedt@goodmis.org, tglx@linutronix.de, thomas.lendacky@amd.com, usama.arif@bytedance.com, will@kernel.org, devicetree@vger.kernel.org, kexec@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org Subject: Re: [PATCH v5 09/16] kexec: enable KHO support for memory preservation Message-ID: References: <20250320015551.2157511-1-changyuanl@google.com> <20250320015551.2157511-10-changyuanl@google.com> <20250321134629.GA252045@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: 427DBC001B X-Stat-Signature: xu8u5w7jqrid3xep35zp7eo4mmdpamtm X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1742990846-443010 X-HE-Meta: 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 Xnf9gVPT IZLgfZdAoSvauwmBtwhtrzJGE4ZfzAz44pPdf7yqHlOjz+rEGiXP0Uv5WFvhqCJ/0mh3YzkhDBtRrEweApNCGsetn11ZTdfCDZHK3gbHJyodAbZVWlkojPH6l1Vyn3jv7tUd9BwjPVcBJbT18dAzQPh9D89Q+O7Jh40ZH8BgRCc151JIjie6sa16OT778+UyRtHY2ANSc5TAdBKoKyK5tEE1EjMSbX3Ko9j3w434mArDCnkZobZIILssen1JlUNZTwLLKep1ILDugBoJGmV8AW/QC17NqCxnZ1d+QoSQ2VnMejU9Ha7ukBPDzmYfYIJUhXsmMmK2EaV//ye8= 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 Mon, Mar 24, 2025 at 05:07:36PM -0300, Jason Gunthorpe wrote: > On Mon, Mar 24, 2025 at 02:18:34PM -0400, Mike Rapoport wrote: > > On Sun, Mar 23, 2025 at 03:55:52PM -0300, Jason Gunthorpe wrote: > > > On Sat, Mar 22, 2025 at 03:12:26PM -0400, Mike Rapoport wrote: > > > > > > > > > + page->private = order; > > > > > > > > > > Can't just set the page order directly? Why use private? > > > > > > > > Setting the order means recreating the folio the way prep_compound_page() > > > > does. I think it's better to postpone it until the folio is requested. This > > > > way it might run after SMP is enabled. > > > > > > I see, that makes sense, but also it could stil use page->order.. > > > > But there's no page->order :) > > I mean this: > > static inline unsigned int folio_order(const struct folio *folio) > { > if (!folio_test_large(folio)) > return 0; > return folio->_flags_1 & 0xff; > } I don't think it's better than page->private, KHO will need to prep_compound_page() anyway so these will be overwritten there. And I don't remember, but having those set before prep_compound_page() might trigger VM_BUG_ON_PGFLAGS(). > Jason -- Sincerely yours, Mike.