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Wed, 04 Nov 2026 14:17:01 -0800 (PST) Received: from [192.168.1.22] ([83.231.69.9]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-4b56ef2e968sm16301645e9.8.2026.11.04.14.17.00 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 04 Nov 2026 14:17:01 -0800 (PST) Message-ID: Date: Wed, 4 Nov 2026 23:17:00 +0100 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] kho: skip zero-sized lowmem and global bootmem areas To: "Mike Rapoport (Microsoft)" , Pasha Tatashin , Pratyush Yadav Cc: Alexander Graf , Andrew Morton , Chen Pei , George Guo , Kexin Liu , Sourabh Jain , kexec@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20261104-kho-bootmem-sizing-v2-0-b0d1a834780f@kernel.org> <20261104-kho-bootmem-sizing-v2-2-b0d1a834780f@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <20261104-kho-bootmem-sizing-v2-2-b0d1a834780f@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/4/26 5:50 PM, Mike Rapoport (Microsoft) wrote: > The lowmem and the global bootmem areas can have zero size, for example > when none or all of the memory is below ARCH_LOW_ADDRESS_LIMIT, or when > either of those areas is explicitly set to zero with kho_bootmem=. > > For a zero-sized allocation memblock returns an address without reserving > anything, and that empty area is recorded in kho_bootmem. If there is no > memory below ARCH_LOW_ADDRESS_LIMIT, allocation of the empty lowmem area > fails and KHO gets disabled. > > Extract a helper that checks for zero size and allocates memory from > memblock, and use it to skip empty areas the same way as empty per-node > areas are skipped. > > Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers") > Reported-by: Chen Pei > Closes: https://lore.kernel.org/all/20261026131851.9942-1-cp0613@linux.alibaba.com > Signed-off-by: Mike Rapoport (Microsoft) Reviewed-by: Jose A. Perez de Azpillaga -- cheers, jose a. p-a