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Sun, 23 Feb 2025 18:50:35 -0800 (PST) Date: Mon, 24 Feb 2025 02:50:34 +0000 From: Wei Yang To: Mike Rapoport Cc: linux-kernel@vger.kernel.org, Alexander Graf , Andrew Morton , Andy Lutomirski , Anthony Yznaga , Arnd Bergmann , Ashish Kalra , Benjamin Herrenschmidt , Borislav Petkov , Catalin Marinas , Dave Hansen , David Woodhouse , Eric Biederman , Ingo Molnar , James Gowans , Jonathan Corbet , Krzysztof Kozlowski , Mark Rutland , Paolo Bonzini , Pasha Tatashin , "H. Peter Anvin" , Peter Zijlstra , Pratyush Yadav , Rob Herring , Rob Herring , Saravana Kannan , Stanislav Kinsburskii , Steven Rostedt , Thomas Gleixner , Tom Lendacky , Usama Arif , Will Deacon , 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 v4 03/14] memblock: Add support for scratch memory Message-ID: <20250224025034.g4htzqgm3r3ja4yy@master> Reply-To: Wei Yang References: <20250206132754.2596694-1-rppt@kernel.org> <20250206132754.2596694-4-rppt@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250206132754.2596694-4-rppt@kernel.org> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspam-User: X-Rspamd-Queue-Id: 5270110000A X-Rspamd-Server: rspam12 X-Stat-Signature: kqmg7hwet3mbawm6988tx8kn1kcmcmzn X-HE-Tag: 1740365438-131069 X-HE-Meta: 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 CXc2bIrE 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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: On Thu, Feb 06, 2025 at 03:27:43PM +0200, Mike Rapoport wrote: >From: Alexander Graf > >With KHO (Kexec HandOver), we need a way to ensure that the new kernel >does not allocate memory on top of any memory regions that the previous >kernel was handing over. But to know where those are, we need to include >them in the memblock.reserved array which may not be big enough to hold >all ranges that need to be persisted across kexec. To resize the array, >we need to allocate memory. That brings us into a catch 22 situation. > >The solution to that is limit memblock allocations to the scratch regions: >safe regions to operate in the case when there is memory that should remain >intact across kexec. > >KHO provides several "scratch regions" as part of its metadata. These >scratch regions are contiguous memory blocks that known not to contain any >memory that should be persisted across kexec. These regions should be large >enough to accommodate all memblock allocations done by the kexeced kernel. > >We introduce a new memblock_set_scratch_only() function that allows KHO to memblock_set_kho_scratch_only? >indicate that any memblock allocation must happen from the scratch regions. > >Later, we may want to perform another KHO kexec. For that, we reuse the >same scratch regions. To ensure that no eventually handed over data gets >allocated inside a scratch region, we flip the semantics of the scratch >region with memblock_clear_scratch_only(): After that call, no allocations memblock_clear_kho_scratch_only? >may happen from scratch memblock regions. We will lift that restriction >in the next patch. > -- Wei Yang Help you, Help me