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Thu, 14 May 2026 10:42:58 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id YZwGEDKnBWp5TgAAD6G6ig (envelope-from ); Thu, 14 May 2026 10:42:58 +0000 Date: Thu, 14 May 2026 12:42:57 +0200 From: Daniel Wagner To: Aaron Tomlin Cc: Daniel Wagner , axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me, mst@redhat.com, aacraid@microsemi.com, James.Bottomley@hansenpartnership.com, martin.petersen@oracle.com, liyihang9@h-partners.com, kashyap.desai@broadcom.com, sumit.saxena@broadcom.com, shivasharan.srikanteshwara@broadcom.com, chandrakanth.patil@broadcom.com, sathya.prakash@broadcom.com, sreekanth.reddy@broadcom.com, suganath-prabu.subramani@broadcom.com, ranjan.kumar@broadcom.com, jinpu.wang@cloud.ionos.com, tglx@kernel.org, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, akpm@linux-foundation.org, maz@kernel.org, ruanjinjie@huawei.com, bigeasy@linutronix.de, yphbchou0911@gmail.com, wagi@kernel.org, frederic@kernel.org, longman@redhat.com, chenridong@huawei.com, hare@suse.de, kch@nvidia.com, ming.lei@redhat.com, tom.leiming@gmail.com, steve@abita.co, sean@ashe.io, chjohnst@gmail.com, neelx@suse.com, mproche@gmail.com, nick.lange@gmail.com, marco.crivellari@suse.com, rishil1999@outlook.com, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v13 5/8] blk-mq: use hk cpus only when isolcpus=io_queue is enabled Message-ID: <70b4cbf0-9137-41de-881b-ff2a60f084ec@flourine.local> References: <20260513005509.135966-1-atomlin@atomlin.com> <20260513005509.135966-6-atomlin@atomlin.com> <3af2cd18-1221-4ff6-aa7f-6dab74460eab@nitrogen.local> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; 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TAGGED_RCPT(0.00)[]; MISSING_XM_UA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; DKIM_TRACE(0.00)[suse.de:+]; R_RATELIMIT(0.00)[to_ip_from(RLip3qrwmtdyuwmp1ydoxr43fi)]; DBL_BLOCKED_OPENRESOLVER(0.00)[suse.de:dkim,imap1.dmz-prg2.suse.org:rdns,imap1.dmz-prg2.suse.org:helo] X-Rspamd-Queue-Id: 5E08962A8F X-Rspamd-Server: rspamd2.dmz-prg2.suse.org X-Spam-Flag: NO X-Spam-Score: -3.01 On Wed, May 13, 2026 at 07:30:44PM -0400, Aaron Tomlin wrote: > > I think this should also check if the CPU is online. The fallback should > > ensure the system will boot. > > While I completely agree with the goal of ensuring a safe boot, I suspect > that we actually must iterate over for_each_possible_cpu(cpu) here to > prevent map boundary violations during CPU hotplug events. I have to check this version of the patch what is happening in detail. Originally the idea was that the fallback should only be taken if it's not possible to create a valid mapping due to $reason. In this case the system should still boot and issue a warning. This is also what the comments says in the function, pick one online CPU and map all hctx to it. Don't bother to be smart.