From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3DA5EC55184 for ; Tue, 4 Aug 2026 15:24:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=XQlD96KP3t1YvDKoOGLaZdhqGhRYm9+1I6FKDrf3KQI=; b=NAYrKY1/+IliHWuBWolKbMvgUg um7cgGFoAN9v7eaQmwCDc/VmcCAUc/GyNQrLHHjGMAFFqoENhx2/ududSP9OH5zPHKP/TZDmA3FWG N7PV9jV+qmy1TQgOqcUC4fF+EIf7ustR6qjRBSvkWmtLwKO4IHR7EMLxIw/dMjMjWczwoEX+rjwo7 FM7ehFbWY2YsVOZs98ygGF0bPfLm9UoI0cQzUF26Jd+4S9RoIB+/bDokhdY8L7lD+iXEkZMGVNb50 JdhBPSLGMXp9Y3k+9pmUx8f3p/zRYF12j87cS91KPZ9zmzEz9syWvrH+e+paGw3ZHGu99aUT2f3e9 Kq1cTpww==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrGzj-00000002Cja-1Ywx; Tue, 04 Aug 2026 15:23:55 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrGzh-00000002CiR-1RNl for linux-arm-kernel@lists.infradead.org; Tue, 04 Aug 2026 15:23:54 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E87651476; Tue, 4 Aug 2026 08:23:44 -0700 (PDT) Received: from [10.2.212.23] (e121345-lin.cambridge.arm.com [10.2.212.23]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 964693F86F; Tue, 4 Aug 2026 08:23:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1785857029; bh=L2JX0u8Lfazn5RuRn03mNfgqAEqgLPIOjbmGYwItSCw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=ccAb3BZcuVgv6XZv+Wh+4/ektkFWGnknlGrl6C5/AvKTMAkCpcmZ/Se+jz8XyyY7c MJ45VhKFzjjjKJ9CGatkCCdLCWaaXlVX0Mtt32vZSBinH1X8BORTfKxjvGqb0YQUtC dsVwghScmdvtTJ2I6Lf+EZ6nDWcnc6NL5za5CmSQ= Message-ID: <57013b4e-d024-4c37-8fb1-5d7c96a13978@arm.com> Date: Tue, 4 Aug 2026 16:23:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] iommu/arm-smmu-v3: Shrink command/event/PRI queues in kdump kernel To: Jason Gunthorpe , Will Deacon Cc: Kiryl Shutsemau , Joerg Roedel , Nicolin Chen , Pranjal Shrivastava , Breno Leitao , Kyle McMartin , Usama Arif , linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org References: <20260706084708.8072-1-kas@kernel.org> <20260804141704.GB27883@nvidia.com> From: Robin Murphy Content-Language: en-GB In-Reply-To: <20260804141704.GB27883@nvidia.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260804_082353_421074_CA8CF68A X-CRM114-Status: GOOD ( 15.49 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 04/08/2026 3:17 pm, Jason Gunthorpe wrote: > On Tue, Aug 04, 2026 at 03:02:46PM +0100, Will Deacon wrote: >>> Would skipping their allocation when is_kdump_kernel() be acceptable on >>> its own, or would you rather see it done differently? >> >> With Nicolin's patch, we can just avoid allocating the priq and the evtq >> entirely in the kdump case. We can then add a cmdline option to control >> the maximum size of the cmdq, which is useful regardless of kdump. > > I would still prefer kdump do this re-sizing automatically, even if we > do add a commandline. It makes it easire to deploy than having to know > secret command lines :\ Right, but if we implement a general command-line option/module parameter/whatever with a variable that needs a default value for when it's not overridden, then it's even more trivial to initialise *that* default value based on further conditions as desired. Plus implementing the more dynamic mechanism to begin with is arguably nicer than hard-coding a kdump special case in what is effectively the wrong place, since semantically what we really want to override/generalise are the max_n_shift initialisations in arm_smmu_device_hw_probe() itself. Thanks, Robin. > So functionally I still think this patch is fine, though yes it points > out more things in Nicolin's work too. > > Jason