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 7283BC55ABF for ; Thu, 6 Aug 2026 13:00:49 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=mW/OuZ6mDAqPwiWKjJo6a74gpl79w+/96YfJnOrsAnE=; b=WeNs3Ert/ndN8pk3YrN8YEOG2o ThJA/6SnKVCEFvm9YHrcZtkCVO6esIEPkv5Gs0/7S84/biDUCiTos/1Otnmbbx3P3ouTWFCKdihBE W2S8L95oqzY4SEbRe6pRhza3XIINb1mbqizQRaXKnE9czG1NYLf6ojbgdEi/i6iDx0mw0XAB3k39B gnd9C3AXRMiDIdkzR0Nc2/9tC/YnkvYqCieYRFxBMFdFVbuQIDTsP8TpyyYHydWyRt+dHQdgSON08 OCcSNilz14dUbbNdfEqGcv/As3SNGvj82UpO3ouzn3RembN/vrHKoI7er7H7nJIHurGjhhF8aUbte otVrCvWg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrxi9-00000005q20-1BI8; Thu, 06 Aug 2026 13:00:37 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wrxi8-00000005q1t-03sh for linux-arm-kernel@lists.infradead.org; Thu, 06 Aug 2026 13:00:36 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id F325B60A96; Thu, 6 Aug 2026 13:00:34 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 52E551F000E9; Thu, 6 Aug 2026 13:00:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1786021234; bh=mW/OuZ6mDAqPwiWKjJo6a74gpl79w+/96YfJnOrsAnE=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=a86oeqp4RR3VHaJpTt4R9aiSI/uw/jdngWhLSd2xywYg+BiVfBYpQynxbLq654MRU O0eRadyZulK73laweC/FpAtNgiIJQgHJdJFnaHTBjNnrblMOj60N2M91wUg+g7OVJC B4v0KVk4P2V+RwWdSjexPi1bzKlWMRWkXQW82wlZvdWz78EIedX7kjxAroGNoiUiXc 8UURMYbrxTSFLK0DK7TKkezyaLdUnMTb3RgxoF0XMEi71Vf5TPw1FXBvR0dTbh/aq6 jBlYPIfOnCUn+I37wjoXKkbxkUDieYBRJQdFx3yC3uPNcmDt8xci5B52/40FIT3qM0 JoNnwfn81OOKQ== Date: Thu, 6 Aug 2026 14:00:28 +0100 From: Will Deacon To: Nicolin Chen Cc: Jason Gunthorpe , Kiryl Shutsemau , Robin Murphy , Joerg Roedel , Pranjal Shrivastava , Breno Leitao , Kyle McMartin , Usama Arif , linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org Subject: Re: [PATCH v3] iommu/arm-smmu-v3: Shrink command/event/PRI queues in kdump kernel Message-ID: References: <20260706084708.8072-1-kas@kernel.org> <20260804141704.GB27883@nvidia.com> <20260804161918.GG27883@nvidia.com> <20260804165905.GH27883@nvidia.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Tue, Aug 04, 2026 at 10:39:13AM -0700, Nicolin Chen wrote: > On Tue, Aug 04, 2026 at 01:59:05PM -0300, Jason Gunthorpe wrote: > > On Tue, Aug 04, 2026 at 09:45:01AM -0700, Nicolin Chen wrote: > > > On Tue, Aug 04, 2026 at 01:19:18PM -0300, Jason Gunthorpe wrote: > > > > On Tue, Aug 04, 2026 at 09:04:32AM -0700, Nicolin Chen wrote: > > > > > On Tue, Aug 04, 2026 at 11:17:04AM -0300, 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 :\ > > > > > > > > > > > > So functionally I still think this patch is fine, though yes it points > > > > > > out more things in Nicolin's work too. > > > > > > > > > > I will send a v10 of mine, to skip the EVTQ/PRIQ allocations. > > > > > > > > I think Robin's point is to structure the v10 so you introduce a bunch > > > > of tunables, including something like 0 size to disable a feature. > > > > > > > > Then have kdump default those tunables to the right thing > > > > > > But in kdump, EVTQ/PRIQ are disabled, so my series should have > > > skipped their allocations regardless of the tunables. > > > > > > So, I think the tunables can be done in a separate series. And > > > its use case might not be confined to kdump? > > > > I think the ask is to do the tunables first and change your series to > > default the tunables instead of doing direct kdump overrides. > > You mean the driver can override the tunables to 0 in kdump mode, > right? > > Well, we are skipping a lot of things in kdump mode already; it's > a very small change to skip EVTQ/PRIQ even without the tunables. > > If Will prefers this merging sequence, I wouldn't mind changing my > series to overriding the tunables. I was thinking that the tunable would only apply to the cmdq. We can extend it later if necessary, but since we're not going to enable the evtq/priq in kdump mode at all, I don't think we need tunables for those atm. I probably wouldn't make a size of 0 disable the queue, either. Have a minimum size of a page or something like that. Will