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Perez de Azpillaga" To: Mike Rapoport , Andrew Morton , Kees Cook , Alexander Graf , Changyuan Lyu 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-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20261021_141108_325305_F51967CD X-CRM114-Status: UNSURE ( 9.97 ) X-CRM114-Notice: Please train this message. X-Spam-Score: -2.1 (--) X-BeenThere: kexec@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Tony Luck , Pasha Tatashin , linux-mm@kvack.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, "Jose A. Perez de Azpillaga" , Pratyush Yadav Sender: "kexec" X-Spam-Status: No, score=-8.8 required=3.0 tests=BAYES_00,DKIM_ADSP_CUSTOM_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,FREEMAIL_FORGED_FROMDOMAIN, FREEMAIL_FROM,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=4.0.1 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