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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1769158429; bh=8xDScLcsy5OFgIJg5rseIw23Z3H5/7lWSJmJgApIXko=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=EJyy6q4GWlNjzBtY8qzSezHb7bGJ0MPYYNHtLo9jOXlGE/DhGzq1hfsdoLsqjLcHB KyHB/f8pdvDLTlYmTUYPNPK3Abt0FTBwhzIVXmzVsQmfZp8XB1Fdam7mJLMGII6GzU vGYWSG3J6wWzp/HHPspEPHFPwJiVIyoFxLIrAQoi8SlYn+5CFFzJUw6NavLlmM8SZc we7Wuh+48gW6nIFohR3yz54yhjHR4iYs2YXbW8XS6JyGqb/xIdxXwTjAIncCpcVpp4 JnJb3EpXp66eRrCBIGWkp71VvVprmAHUEBHJVAXxdycnZQtMG+rVlM2T1F+sYDB5UL o13nTXz1H/wWw== Date: Fri, 23 Jan 2026 10:53:42 +0200 From: Mike Rapoport To: Andrew Morton Cc: Evangelos Petrongonas , Pasha Tatashin , Pratyush Yadav , Alexander Graf , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Subject: Re: [PATCH v2] kho: skip memoryless NUMA nodes when reserving scratch areas Message-ID: References: <20260120175913.34368-1-epetron@amazon.de> <20260122152112.1a8be8e7bdab72631234cd69@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260122152112.1a8be8e7bdab72631234cd69@linux-foundation.org> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 94F53180003 X-Stat-Signature: o4kn4toncmrtq8y3qgm4prxumyfszszn X-HE-Tag: 1769158430-18561 X-HE-Meta: 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 8mZ9VWkH XzLT7Vi2P4cUkPGoJkkGS19bQMT1ntuLf0l396XtGR9kkbnPcJEGYfiMVZA/gz75ynAvt1OGHqhFNm8KCXcvsB+J6Pq2+Cd+AjgQ5ZT2umh3jNVLQTW6E0thos1sF2JvPJLes0cXK1t28Xsx49GZheejK++rJT0xvwN5wK5vAhFNTt4OYr0/58ebOgFFSXuC3ZML83o5INguHUge8ND1j4UhpvBjMcNgpNjk/eh9YwdHLrjl63vB25GLj8jtedz83MUO7 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: On Thu, Jan 22, 2026 at 03:21:12PM -0800, Andrew Morton wrote: > On Tue, 20 Jan 2026 17:59:11 +0000 Evangelos Petrongonas wrote: > > > kho_reserve_scratch() iterates over all online NUMA nodes to allocate > > per-node scratch memory. On systems with memoryless NUMA nodes (nodes > > that have CPUs but no memory), memblock_alloc_range_nid() fails because > > there is no memory available on that node. This causes KHO initialization > > to fail and kho_enable to be set to false. > > > > Some ARM64 systems have NUMA topologies where certain nodes contain only > > CPUs without any associated memory. These configurations are valid and > > should not prevent KHO from functioning. > > > > Fix this by only counting nodes that have memory (N_MEMORY state) and > > skip memoryless nodes in the per-node scratch allocation loop. > > > > So kho is unusable on such machines. > > Should we backport this? I'm thinking > > Fixes: 3dc92c311498 ("kexec: add Kexec HandOver (KHO) generation helpers"). It's only for v6.18, but sure, why not. -- Sincerely yours, Mike.