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 0E2681775C for ; Wed, 9 Aug 2023 11:23:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BB94EC433C9; Wed, 9 Aug 2023 11:23:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1691580203; bh=/Jo698VUwWViOfRpDRaOF+geLJTlE2ZHuvKqfJHymbg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=cBVsEVdhjXnSoLGT3ZxfxQMdwIpTlHwYq31bkpyXuEt3FKgzMn8pbVUhgqStXya3/ lcw+9dGGF+1Q2BZm2cJN1Bdpt/evjLRT4YVvAK3z0rqt5GvfgApsICmtIccmpgYJ3j YqiB4ahG1XIRUzI46dqIU1Ak6syGoPR0U9TFSJI8QUej/PICfsZ+svckYc07Q5qvJB a2g6nLd6G6ySr9vZQwcBIWNY54wilqzqqTl7QJVOXMAHcjGDfZSH6Oq95MsYvjZe/K YVFsSCCj4vJVlaU8xQoWXU+92Gt7AaZzj61uWagT0lOfsBREbBYGUSD1iX1/Rumki7 MjGIxfMUma2yw== Date: Wed, 9 Aug 2023 12:23:18 +0100 From: Will Deacon To: zhurui Cc: Robin Murphy , Nicolin Chen , linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev, linux-kernel@vger.kernel.org, Joerg Roedel , Lu Baolu , Jason Gunthorpe , Yicong Yang , Tomas Krcka , Jean-Philippe Brucker Subject: Re: [PATCH v2 1/1] iommu/arm-smmu-v3: Fix error case of range command Message-ID: <20230809112317.GA3830@willie-the-truck> References: <20230801085504.GA26130@willie-the-truck> <27c895b8-1fb0-be88-8bc3-878d754684c8@huawei.com> <20230804165225.GF30679@willie-the-truck> <015b4573-9d74-451b-8028-a1050ade7019@huawei.com> <661a7bb5-99e1-de16-d860-0cd17f7a0470@arm.com> <20230808162409.GB2890@willie-the-truck> <80ead8ee-4dbe-7b3c-44f5-944073a2a39d@arm.com> <412886be-644a-5b46-9bfa-1c9a358f9a5d@huawei.com> Precedence: bulk X-Mailing-List: iommu@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <412886be-644a-5b46-9bfa-1c9a358f9a5d@huawei.com> User-Agent: Mutt/1.10.1 (2018-07-13) On Wed, Aug 09, 2023 at 05:22:06PM +0800, zhurui wrote: > On 2023/8/9 0:43, Robin Murphy wrote: > > On 08/08/2023 5:24 pm, Will Deacon wrote: > >> On Mon, Aug 07, 2023 at 08:20:45PM +0100, Robin Murphy wrote: > >>> Yeah, I'd rather not downgrade to a non-range invalidate since that > >>> complicates the reasoning for the errata affecting those. If the size of the > >>> invalidation is equal to TG then it can only represent a single last-level > >>> page, i.e. TTL=3, thus if it does warrant handling here then indeed > >>> rearranging to base the condition on num_pages as well ought to suffice. > >>> However, this is all still begging the question of where and why we're doing > >>> a *non-leaf* invalidation that isn't aligned to the size of a table, because > >>> that in itself doesn't make a whole heap of sense - my hunch is that that > >>> wants figuring out and could probably be fixed at the source. > >> > >> Isn't that described above because we're using CMDQ_TLBI_RANGE_NUM_MAX > >> to break up the range into separate commands? > > > > Not really, because if we're doing a genuine non-leaf invalidation of a > > table then it should be a block-aligned range that ought to fit in a > > single command and should certainly never involve a single-granule > > remainder. If we're doing non-leaf invalidations of things that > > logically don't need to be non-leaf, making them leaf would be the even > > better option. > > > > I agree with Robin that if the caller is doing a genuine non-leaf invalidation > of a table, it should not involve a single-granule tlbi. It seems that the > caller only filter the block size, but not the address aligned or not maybe. There's only one caller though, right? That's the io_pgtable_tlb_flush_walk() call in io-pgtable-arm.c which shouldn't trigger this problem. Do you have a backtrace for the case when we generate the illegal command? > >> Do you mind if I queue the patch as-is for now? I don't think the driver > >> should be emitting illegal commands, and v2 of the patch does seem like > >> the obvious thing to do. > > > > TBH I'd rather you just drop my patch if it's proven problematic, and > > I'll take another crack at it soon. The potential problems we introduce > > by using non-range invalidates on errata-affected MMU-700 revisions are > > worse than the almost-entirely-theoretical one I was trying to address. > > > > If you all agree to roll back the problematic code, is the first patch be OK? > Should I need to add some more descriptions to clarify this? I can just go and revert Robin's original patch, but I'd like to see your backtrace first so that we understand how this is occurring. Thanks, Will