From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id B0C714611E7; Wed, 21 Jan 2026 08:38:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768984700; cv=none; b=swywSRwQNrP49GFNuN0csy5uatl7MDAmTTh/L9LeUw2+JFgbWgys8duR3fMA+3auuVjnKDQ7J4UI2+1dzRBSw1TfsWNPNf+gejmeTALW8Tt5vqbR5hDaIRHBnB4PIihgHdeFcUtb482CD49SHWMPg+SGT0uppwDyqKqnzZDS+nI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768984700; c=relaxed/simple; bh=FHIfrtQp0a1LDUro16fPEm1A1xfk5VxSFyVP/6ghJZY=; h=Date:Message-ID:From:To:Cc:Subject:In-Reply-To:References: MIME-Version:Content-Type; b=ccKysp3EM7C23Qhy2GFgxWce5KBjnr3lL00rts0YDFi3lK+aM+Y37Zj70qA7pOaHz83kbn5hPPtCcbzKcO7K1ShzUdxLizX8ITCalaToZaIbO7RdKukK1t2YkqxLOsrtxfKytTa3WgAgPQCJZiEURVqedW68vXFK0yBPM/+FIKY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=rL3quvkl; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="rL3quvkl" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 234DAC116D0; Wed, 21 Jan 2026 08:38:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1768984700; bh=FHIfrtQp0a1LDUro16fPEm1A1xfk5VxSFyVP/6ghJZY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=rL3quvklhfag30JMrlUH5pn2+ingfQ7mybc6tPSgCAYfkq83LleY2B9rp0FE1qJKb WdgzJAP8E8Ic2BXuWUVxBkcy4lbc7a/ruvwX//10Aqdjk201PLSdG9v/RqjP3BFoHQ vmk7smtLQsXcV0+CHWWSVmGoT5EU1/vFcfyILjS2Tu56IUnBC0V52yr/yLfJOsp6EZ s9FSXNg7zW92Cnkm5gW2YzAvAqms7QxJYdYwDqgvtTp0jgpGTSTj0J+8xacNAg+/Mj KHuo54s424Vw3l7CsR5t2M3GCnZ2LGGLTOstBmxv4y1EleFMKBaO+qfE8RrFJcKcte Puu0JUyyNb8SQ== Received: from sofa.misterjones.org ([185.219.108.64] helo=goblin-girl.misterjones.org) by disco-boy.misterjones.org with esmtpsa (TLS1.3) tls TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384 (Exim 4.98.2) (envelope-from ) id 1viTjF-00000004Ewn-2tx9; Wed, 21 Jan 2026 08:38:17 +0000 Date: Wed, 21 Jan 2026 08:38:17 +0000 Message-ID: <861pjjcqdi.wl-maz@kernel.org> From: Marc Zyngier To: Waiman Long , Thomas Gleixner Cc: Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev Subject: Re: [PATCH] irqchip/gic-v3-its: Don't acquire rt_spin_lock in allocate_vpe_l1_table() In-Reply-To: <86tswrkrh4.wl-maz@kernel.org> References: <20260107215353.75612-1-longman@redhat.com> <864iowmrx6.wl-maz@kernel.org> <87ms2nsqju.ffs@tglx> <86wm1qlq7l.wl-maz@kernel.org> <87ecnwij44.ffs@tglx> <86v7h8l9ht.wl-maz@kernel.org> <87pl7gglya.ffs@tglx> <86tswrkrh4.wl-maz@kernel.org> User-Agent: Wanderlust/2.15.9 (Almost Unreal) SEMI-EPG/1.14.7 (Harue) FLIM-LB/1.14.9 (=?UTF-8?B?R29qxY0=?=) APEL-LB/10.8 EasyPG/1.0.0 Emacs/30.1 (aarch64-unknown-linux-gnu) MULE/6.0 (HANACHIRUSATO) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 (generated by SEMI-EPG 1.14.7 - "Harue") Content-Type: text/plain; charset=US-ASCII X-SA-Exim-Connect-IP: 185.219.108.64 X-SA-Exim-Rcpt-To: longman@redhat.com, tglx@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, rostedt@goodmis.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev X-SA-Exim-Mail-From: maz@kernel.org X-SA-Exim-Scanned: No (on disco-boy.misterjones.org); SAEximRunCond expanded to false On Mon, 12 Jan 2026 11:20:07 +0000, Marc Zyngier wrote: > > On Sun, 11 Jan 2026 16:20:45 +0000, > Thomas Gleixner wrote: > > > > On Sun, Jan 11 2026 at 10:38, Marc Zyngier wrote: > > > On Sun, 11 Jan 2026 09:39:07 +0000, > > > Thomas Gleixner wrote: > > >> > > >> On Fri, Jan 09 2026 at 16:13, Marc Zyngier wrote: > > >> > On Thu, 08 Jan 2026 22:11:33 +0000, > > >> > Thomas Gleixner wrote: > > >> >> At the point where a CPU is brought up, the topology should be known > > >> >> already, which means this can be allocated on the control CPU _before_ > > >> >> the new CPU comes up, no? > > >> > > > >> > No. Each CPU finds *itself* in the forest of redistributors, and from > > >> > there tries to find whether it has some shared resource with a CPU > > >> > that has booted before it. That's because firmware is absolutely awful > > >> > and can't present a consistent view of the system. > > >> > > >> Groan.... > > >> > > >> > Anyway, I expect it could be solved by moving this part of the init to > > >> > an ONLINE HP callback. > > >> > > >> Which needs to be before CPUHP_AP_IRQ_AFFINITY_ONLINE, but even that > > >> might be to late because there are callbacks in the STARTING section, > > >> i.e. timer, perf, which might rely on interrupts being accessible. > > > > > > Nah. This stuff is only for direct injection of vLPIs into guests, so > > > as long as this is done before we can schedule a vcpu on this physical > > > CPU, we're good. No physical interrupt is concerned with this code. > > > > That's fine then. vCPUs are considered "user-space" tasks and can't be > > scheduled before CPUHP_AP_ACTIVE sets the CPU active for the scheduler. > > Waiman, can you please give the following hack a go on your box? The > machines I have are thankfully limited to a single ITS group, so I > can't directly reproduce your issue. Have you managed to try this hack? I may be able to spend some time addressing the issue in the next cycle if I have an indication that I'm on the right track. Thanks, M. -- Without deviation from the norm, progress is not possible.