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Wysocki" , Steven Chen , Yan Zhao , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [RFC v1 0/4] Make KHO Stateless Message-ID: References: <20250917025019.1585041-1-jasonmiu@google.com> <20250917113609.GB1086830@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250917113609.GB1086830@nvidia.com> X-Rspamd-Queue-Id: 52E46140007 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: fi8d1q7gxpnshpoomh1xaqx5bpp5ooeg X-HE-Tag: 1758493579-990467 X-HE-Meta: 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 3og3alMr x0HxfKgDjz0/ce5g5exyQovBkg9JelGWU/r6zKA6q6wmpAyAcrJpSvvgKXEYnEXxwypdQHDAZcEb3GBCsSg4rC7denWy/0z//JS4VnX2eS0mA1XdbaP/A4fTfXw00aoUklQAIuh8Crr1i4PU= 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 Wed, Sep 17, 2025 at 08:36:09AM -0300, Jason Gunthorpe wrote: > On Tue, Sep 16, 2025 at 07:50:15PM -0700, Jason Miu wrote: > > This series transitions KHO from an xarray-based metadata tracking > > system with serialization to using page table like data structures > > that can be passed directly to the next kernel. > > > > The key motivations for this change are to: > > - Eliminate the need for data serialization before kexec. > > - Remove the former KHO state machine by deprecating the finalize > > and abort states. > > - Pass preservation metadata more directly to the next kernel via the FDT. > > > > The new approach uses a per-order page table structure (kho_order_table, > > kho_page_table, kho_bitmap_table) to mark preserved pages. The physical > > address of the root `kho_order_table` is passed in the FDT, allowing the > > next kernel to reconstruct the preserved memory map. > > It is not a "page table" structure, it is just a radix tree with bits > as the leaf. Sounds like the IDA data structure. Maybe that API needs to be enhanced for this use case, but surely using the same data structure would be a good thing?