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b=UHn0uj+sFtGKGaLst/9muipxKqjAxKUpZ+JoQnL+duqe8G78dsi/abK5ag6CP9hJm OP5wzOYOlDurhfr842HXp3hCAWB8YDNogKdbp/kzN6pDU7wNgpzn5749pSO1boCZlt 6wKejwWgFp+/su6c8JaDG20/CEgau226J8buSe7UDs9TKi6Sya0uZAbn2NkUxGa0fo Et6Ef7UU2hOmBhoAKI5VBA2QYe5TXWmSOwZBsfBCWaIAh+OEfwpcnPN03mNODB/uDY ZVJy6DuuviuuIuoQaLsxRS67TEQW/x2dI791szWv2aYwJ9hb0qxQUwxo47LjbLxQwd 9MBtuukDIdtTw== From: Pratyush Yadav To: "Mike Rapoport (Microsoft)" Cc: Pasha Tatashin , Pratyush Yadav , Alexander Graf , Andrew Morton , Chen Pei , George Guo , Kexin Liu , Sourabh Jain , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 2/3] kho: skip zero-sized lowmem and global bootmem areas In-Reply-To: <20261104-kho-bootmem-sizing-v2-2-b0d1a834780f@kernel.org> (Mike Rapoport's message of "Wed, 04 Nov 2026 18:50:10 +0200") References: <20261104-kho-bootmem-sizing-v2-0-b0d1a834780f@kernel.org> <20261104-kho-bootmem-sizing-v2-2-b0d1a834780f@kernel.org> Date: Tue, 10 Nov 2026 17:55:04 +0100 Message-ID: <2vxzy0b0hbiv.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain X-Rspamd-Server: rspam06 X-Stat-Signature: 9jus9je3g58qobd7gd8hhg7fgi419m6x X-Spam-Status: No, score=-12.3 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS, USER_AGENT_SANE_1 autolearn=unavailable autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: 8D22120002 X-Rspam-User: X-HE-Tag: 1794329709-959111 X-HE-Meta: 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 5xNhVgJC 3yK03FW1mcvSbo8c83NRCiaptAsu1VUQ9PNSHiZGGLm0fqlCHl9RJM/3an0ysSoU0DhbhyS4L7p43S9PigPduQW+qgJ5qpQHK1cvsFUCH1Nj9qQOE+m3YkS1PNX2Ymo12BzZ7N8j4tg+imoYLwN+LXX91wAHsuIuShlx3WEGf6ofOWubQwfqY2UvyLZ/IA7A/k0kGTwqxAQq0yNnt8pyjKdNDvRK9RmLshMJaLPUOe4iERkOy6Xg4XvFYDcKvIrP06B+H Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Wed, Nov 04 2026, Mike Rapoport (Microsoft) wrote: > The lowmem and the global bootmem areas can have zero size, for example > when none or all of the memory is below ARCH_LOW_ADDRESS_LIMIT, or when > either of those areas is explicitly set to zero with kho_bootmem=. > > For a zero-sized allocation memblock returns an address without reserving > anything, and that empty area is recorded in kho_bootmem. If there is no > memory below ARCH_LOW_ADDRESS_LIMIT, allocation of the empty lowmem area > fails and KHO gets disabled. > > Extract a helper that checks for zero size and allocates memory from > memblock, and use it to skip empty areas the same way as empty per-node > areas are skipped. > > Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers") > Reported-by: Chen Pei > Closes: https://lore.kernel.org/all/20261026131851.9942-1-cp0613@linux.alibaba.com > Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Pratyush Yadav [...] -- Regards, Pratyush Yadav