From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 8EA123CB57D for ; Tue, 4 Aug 2026 15:23:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785857031; cv=none; b=gfnutTVV81228dDgHTddctcgaacJNQlkeb41cYlXhZk4Fo/FGdeAtI30/B0zepBg0xVQL61T0slNaVk068b0o9NJccfafwmYJ+pbA/npsJGGvdgRrP14HhHk9it9YLt7eHBbi7DGA3gIhwR5/MoYdzpbqWZogJGYh6W5/jMBsFM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785857031; c=relaxed/simple; bh=L2JX0u8Lfazn5RuRn03mNfgqAEqgLPIOjbmGYwItSCw=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jkPh621IWJdCr6octEuOwEnAk8mafFSQ4J8y+JjUb+e6FmaGGZgegpxYov5V13+LgWSMGUHa212ukP+dJKr6x/cGBkd7PFO1mwuWfRT+lVfS1LFoBey742Ne7A4e0OVlmqjvbvgwRW2KzmTg4pW2iwtoitAX6JHk7MMhstJFo+Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=ccAb3BZc; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="ccAb3BZc" 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 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: 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 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