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b=ud+384l+yB+aELzmFdX7l8ibIN7y+5+njLdeHK50/JSiAcJyiiGlkjjdtAKjHeBD4 hoQuD1jM3uSCM4t9yQgEceDsegFq6IHknfeOcqrWnRbDrmwKbx/RA2TtkB+W9AIaWW voxc3Piq7yG30t/8HGvKwdBisNooq4awkV/1xR9nwZDAn86BqbV+te3BncQtbUoll3 MjnbP3UmazmSq+nS4COmTb0OMtg5b2lQ0qM6+wFgaUOohKM9E/7DLArNeo0fBID4QC GXqFpHbnzeiMJN9E79HfRc+ILd9QLcZVOFEqn6kc68RQBGIYIJXCqWSpdHOreAc7RR jNwu3Li3A/NVA== From: Pratyush Yadav To: Pasha Tatashin Cc: akpm@linux-foundation.org, rppt@kernel.org, graf@amazon.com, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, pratyush@kernel.org, ricardo.neri-calderon@linux.intel.com Subject: Re: [PATCH v4] kho: validate preserved memory map during population In-Reply-To: <20251223140140.2090337-1-pasha.tatashin@soleen.com> (Pasha Tatashin's message of "Tue, 23 Dec 2025 09:01:40 -0500") References: <20251223140140.2090337-1-pasha.tatashin@soleen.com> Date: Tue, 23 Dec 2025 15:11:18 +0100 Message-ID: <86y0mtb855.fsf@kernel.org> User-Agent: Gnus/5.13 (Gnus v5.13) MIME-Version: 1.0 Content-Type: text/plain X-Stat-Signature: ucqopy9yhpfszmw1u8msrxr7xa1otfuc X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 4C52640002 X-HE-Tag: 1766499085-465269 X-HE-Meta: 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 6mn2il4V sdEKZFRAwRyuOhc/O5ocnyzWPy3NyiVysONHwrDmqJ1g664faWO0Wo1gVOwF8Aqnsqex9ymCcZwjJIx11kYX+nxx3ofwKCRKHouOqQp3l1HJBn2urKBgXZjOp00Op94CpQDYqwNJbq5iysC8/bV+JWTfK2dlPcdtyxvRywpwUQOZvfeY/LEaE1Cg78T5q7cczVplov6wQl6rz3K+mVrsNGogyZ8mC9vXAh2v8CuLQouJmslIatv2+94VMaHdliJuYdBmdIaKxsCSRrOqzz9RpNKkLWw== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Dec 23 2025, Pasha Tatashin wrote: > If the previous kernel enabled KHO but did not call kho_finalize() > (e.g., CONFIG_LIVEUPDATE=n or userspace skipped the finalization step), > the 'preserved-memory-map' property in the FDT remains empty/zero. > > Previously, kho_populate() would succeed regardless of the memory map's > state, reserving the incoming scratch regions in memblock. However, > kho_memory_init() would later fail to deserialize the empty map. By that > time, the scratch regions were already registered, leading to partial > initialization and subsequent list corruption (freeing scratch area > twice) during kho_init(). > > Move the validation of the preserved memory map earlier into > kho_populate(). If the memory map is empty/NULL: > 1. Abort kho_populate() immediately with -ENOENT. > 2. Do not register or reserve the incoming scratch memory, allowing the new > kernel to reclaim those pages as standard free memory. > 3. Leave the global 'kho_in' state uninitialized. > > Consequently, kho_memory_init() sees no active KHO context > (kho_in.mem_chunks_phys is 0) and falls back to kho_reserve_scratch(), > allocating fresh scratch memory as if it were a standard cold boot. > > Fixes: de51999e687c ("kho: allow memory preservation state updates after finalization") > Reported-by: Ricardo Neri > Closes: https://lore.kernel.org/all/20251218215613.GA17304@ranerica-svr.sc.intel.com > Signed-off-by: Pasha Tatashin > Reviewed-by: Mike Rapoport (Microsoft) > Tested-by: Ricardo Neri Reviewed-by: Pratyush Yadav [...] -- Regards, Pratyush Yadav