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Thu, 27 Nov 2025 12:37:40 -0800 (PST) From: Usama Arif To: rppt@kernel.org, Andrew Morton Cc: kas@kernel.org, changyuanl@google.com, graf@amazon.com, leitao@debian.org, thevlad@meta.com, pratyush@kernel.org, dave.hansen@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, Usama Arif Subject: [PATCH v2 2/2] mm/memblock: only mark/clear KHO scratch memory when needed Date: Thu, 27 Nov 2025 20:33:20 +0000 Message-ID: <20251127203724.3177621-3-usamaarif642@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251127203724.3177621-1-usamaarif642@gmail.com> References: <20251127203724.3177621-1-usamaarif642@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" The scratch memory for kexec handover is used to bootstrap the kexec'ed kernel. It is only needed when CONFIG_KEXEC_HANDOVER is enabled and only if it is a KHO boot. Add checks to prevent marking a KHO scratch region unless needed. Fixes: a2daf83e10378 ("x86/e820: temporarily enable KHO scratch for memory = below 1M") Reported-by: Vlad Poenaru Signed-off-by: Usama Arif Reviewed-by: Pratyush Yadav --- mm/memblock.c | 74 ++++++++++++++++++++++++++++++--------------------- 1 file changed, 44 insertions(+), 30 deletions(-) diff --git a/mm/memblock.c b/mm/memblock.c index 8b13d5c28922a..8a2cebcfe0a18 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -1114,36 +1114,6 @@ int __init_memblock memblock_reserved_mark_noinit(ph= ys_addr_t base, phys_addr_t MEMBLOCK_RSRV_NOINIT); } =20 -/** - * memblock_mark_kho_scratch - Mark a memory region as MEMBLOCK_KHO_SCRATC= H. - * @base: the base phys addr of the region - * @size: the size of the region - * - * Only memory regions marked with %MEMBLOCK_KHO_SCRATCH will be considered - * for allocations during early boot with kexec handover. - * - * Return: 0 on success, -errno on failure. - */ -__init int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size) -{ - return memblock_setclr_flag(&memblock.memory, base, size, 1, - MEMBLOCK_KHO_SCRATCH); -} - -/** - * memblock_clear_kho_scratch - Clear MEMBLOCK_KHO_SCRATCH flag for a - * specified region. - * @base: the base phys addr of the region - * @size: the size of the region - * - * Return: 0 on success, -errno on failure. - */ -__init int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size) -{ - return memblock_setclr_flag(&memblock.memory, base, size, 0, - MEMBLOCK_KHO_SCRATCH); -} - static bool should_skip_region(struct memblock_type *type, struct memblock_region *m, int nid, int flags) @@ -2617,12 +2587,56 @@ static bool __init reserve_mem_kho_revive(const cha= r *name, phys_addr_t size, =20 return true; } + +/** + * memblock_mark_kho_scratch - Mark a memory region as MEMBLOCK_KHO_SCRATC= H. + * @base: the base phys addr of the region + * @size: the size of the region + * + * Only memory regions marked with %MEMBLOCK_KHO_SCRATCH will be considered + * for allocations during early boot with kexec handover. + * + * Return: 0 on success, -errno on failure. + */ +__init int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size) +{ + if (is_kho_boot()) + return memblock_setclr_flag(&memblock.memory, base, size, 1, + MEMBLOCK_KHO_SCRATCH); + return 0; +} + +/** + * memblock_clear_kho_scratch - Clear MEMBLOCK_KHO_SCRATCH flag for a + * specified region. + * @base: the base phys addr of the region + * @size: the size of the region + * + * Return: 0 on success, -errno on failure. + */ +__init int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size) +{ + if (is_kho_boot()) + return memblock_setclr_flag(&memblock.memory, base, size, 0, + MEMBLOCK_KHO_SCRATCH); + return 0; +} #else static bool __init reserve_mem_kho_revive(const char *name, phys_addr_t si= ze, phys_addr_t align) { return false; } + +__init int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size) +{ + return 0; +} + +__init int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size) +{ + return 0; +} #endif /* CONFIG_KEXEC_HANDOVER */ =20 /* --=20 2.47.3