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Perez de Azpillaga" To: Mike Rapoport , Andrew Morton , Kees Cook , Alexander Graf , Changyuan Lyu Cc: Tony Luck , "Guilherme G. Piccoli" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Pratyush Yadav , Pasha Tatashin , kexec@lists.infradead.org, "Jose A. Perez de Azpillaga" Subject: [RFC PATCH 0/2] memblock: keep reserve_mem regions out of KHO bootmem Date: Wed, 21 Oct 2026 23:10:44 +0200 Message-ID: <20261021211058.83483-1-azpijr@gmail.com> X-Mailer: git-send-email 2.55.0 X-Archived-By: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 3F5BD4000D X-Stat-Signature: 6c849motb5s6yz9izygzrinsysp4sq7r X-Rspam-User: X-Spam-Status: No, score=-10.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_PASS,SPF_PASS,USER_AGENT_GIT autolearn=ham autolearn_force=no version=4.0.1 X-HE-Tag: 1792617067-169275 X-HE-Meta: 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 NbygRV5h bckwvIO1I7Rgnx9tqDkKHJPNj3WB0xGPp+kpiwFPjLxQ3pjWzaC8cStgNNKFETVRu0CpEVNBzUfky9Mp7xLVsAXgMuBXP4wB7q2yJ9sPfaLoKVyubi/vybgMIB8JvDwFOjvHgqpPsO5k/uXigE+XJoqZzFNdypbG0lw3RejyeijJwNj9Wg81DmncXS0jk8yL5DzkEFPIBRZsjqJX8o6J5sywkbfYigokmUqsz3ms6rTgAfkuyWXoOwL4SqpDezMkw1n+Y/RL6X9jPfyLpj1g1neBoljO6bbW25uUCkfmavVLht68nGTsCpHTX0WgHV6yr3JFXQPwUrCgEy4kUbWeJvenoXCtUtDVO648taZdropjHctrykn8mLprvFlCatHc2PgDdLKv5Jrp4h04pIzokbU6JH3DXfn2JNDgGm0pHFD2VwZbZFZUD4kygkw== 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 a KHO boot, a reserve_mem= region that can't be revived (new name, size or alignment) can be allocated from KHO bootmem, which the next kernel boots out of. With CONFIG_KEXEC_HANDOVER_DEBUG preserving it fails; without it, the next kernel's memmap ends up on top of it. Patch 1 factors the bootmem check out of memblock_alloc_hugetlb(), and patch 2 uses it for reserve_mem. That also drops the TODO in reserve_mem(), which asks for the allocation to be outside KHO_NOPRSRV, though it's bootmem it has to stay out of. Questions: - If kho_discover_noprsrv() fails, only bootmem is NOPRSRV, and reserve_mem() now fails with -ENOMEM instead of using it. Is that the right thing to do? - Should reserve_mem skip mirrored memory like HugeTLB does, rather than keep the fallback? No Cc: stable, since patch 2 relies on 14773e2aa4c5 ("kho: extend scratch") for room outside bootmem. Based on next-20261021, as it needs the KHO bootmem rename from liveupdate-7.4 and touches code changed in memblock for-next. Tested on x86_64 in QEMU. Jose A. Perez de Azpillaga (2): memblock: factor out the KHO bootmem check from memblock_alloc_hugetlb() memblock: don't allocate reserve_mem regions from KHO bootmem mm/memblock.c | 100 ++++++++++++++++++++++++++++++++------------------ 1 file changed, 64 insertions(+), 36 deletions(-) base-commit: 9a482184d910775cf648863148944945b74e2815 -- 2.55.0