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[109.81.80.251]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-4324493fe32sm4092572f8f.14.2025.12.18.01.30.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 18 Dec 2025 01:30:34 -0800 (PST) Date: Thu, 18 Dec 2025 10:30:33 +0100 From: Michal Hocko To: Yeoreum Yun Cc: akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, martin.lau@linux.dev, eddyz87@gmail.com, song@kernel.org, yonghong.song@linux.dev, john.fastabend@gmail.com, kpsingh@kernel.org, sdf@fomichev.me, haoluo@google.com, jolsa@kernel.org, jackmanb@google.com, hannes@cmpxchg.org, ziy@nvidia.com, bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org, catalin.marinas@arm.com, will@kernel.org, ryan.roberts@arm.com, kevin.brodsky@arm.com, dev.jain@arm.com, yang@os.amperecomputing.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, bpf@vger.kernel.org, linux-rt-devel@lists.linux.dev, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCH 2/2] arm64: mmu: use pagetable_alloc_nolock() while stop_machine() Message-ID: References: <20251212161832.2067134-1-yeoreum.yun@arm.com> <20251212161832.2067134-3-yeoreum.yun@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20251212161832.2067134-3-yeoreum.yun@arm.com> X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 25B3C1C000F X-Stat-Signature: u4ccsjpdjp5uo3gnh1tbo4nhky7y18hu X-HE-Tag: 1766050236-566686 X-HE-Meta: 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 VjZ8j1OZ Ez/V95OVgptXUT16jG/fNfmdx3lLLrFoFtLfOyBaaoozi7ajQOy2VinePiZM7SEkjHYQ7QeV9EWwjR/+wGQoDNhuzCiJkBBjY8IgRjegXstJnBBbwa/jtbEhY1zV3o5pKfrbYYoWxT+Qh7xTZ13OjWjSfQuQafHauwgu/dPND1018QisKDk8i+kjTqUB0WptSd0xC1sjgFYL5vq5wySemfAC28VISdR86yN1YSyIOSZCmFAcFFx7OaPKlTNGFK1Qn8t84UD/Rf261N1E0emrSqIQC5dB9OnM6KJPid3QEYEo37RAs31IwbPUfM3H6/FwxxCdgIQTrcZapxJJJOw3/gpWUWLDVCCGtW6FGj6JpewX7xCTGS0vrDJf+f2cfjyi5n1XYLT5X36RdtxAFUVB/g+y6lTAkjwe74PJr9vE4HGdQcJzeZ6C60dTvuGlcEc2y6ZVZ3y/1qjbhb4dfS9cTtOLGCUSPdf3brNtj 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 Fri 12-12-25 16:18:32, Yeoreum Yun wrote: > linear_map_split_to_ptes() and __kpti_install_ng_mappings() > are called as callback of stop_machine(). > That means these functions context are preemption disabled. > > Unfortunately, under PREEMPT_RT, the pagetable_alloc() or > __get_free_pages() couldn't be called in this context > since spin lock that becomes sleepable on RT, > potentially causing a sleep during page allocation. > > To address this, pagetable_alloc_nolock(). As you cannot tolerate allocation failure and this is pretty much permanent allocation (AFAIU) why don't you use a static allocation? -- Michal Hocko SUSE Labs