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Fri, 28 Nov 2025 09:33:16 -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 v3 2/2] mm/memblock: only mark/clear KHO scratch memory when needed Date: Fri, 28 Nov 2025 17:29:34 +0000 Message-ID: <20251128173257.969322-3-usamaarif642@gmail.com> X-Mailer: git-send-email 2.47.3 In-Reply-To: <20251128173257.969322-1-usamaarif642@gmail.com> References: <20251128173257.969322-1-usamaarif642@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: xux84gy79ubyoyjgy36haf8wtmoj8yob X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 5945440014 X-HE-Tag: 1764351198-913529 X-HE-Meta: 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 zHwiehL9 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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: The scratch memory for kexec handover is used to bootstrap the kexec'ed kernel. Only the 1st 1MB is used as scratch, and its a hack to get around limitations with KHO. It is only needed when CONFIG_KEXEC_HANDOVER is enabled and only if it is a KHO boot (both checked by is_kho_boot). Add check 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 | 14 +++++++++----- 1 file changed, 9 insertions(+), 5 deletions(-) diff --git a/mm/memblock.c b/mm/memblock.c index 8b13d5c28922a..913cf322eb89a 100644 --- a/mm/memblock.c +++ b/mm/memblock.c @@ -20,8 +20,8 @@ #ifdef CONFIG_KEXEC_HANDOVER #include -#include #endif /* CONFIG_KEXEC_HANDOVER */ +#include #include #include @@ -1126,8 +1126,10 @@ int __init_memblock memblock_reserved_mark_noinit(phys_addr_t base, phys_addr_t */ __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); + if (is_kho_boot()) + return memblock_setclr_flag(&memblock.memory, base, size, 1, + MEMBLOCK_KHO_SCRATCH); + return 0; } /** @@ -1140,8 +1142,10 @@ __init int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size) */ __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); + if (is_kho_boot()) + return memblock_setclr_flag(&memblock.memory, base, size, 0, + MEMBLOCK_KHO_SCRATCH); + return 0; } static bool should_skip_region(struct memblock_type *type, -- 2.47.3