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Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1luCWt-00DrR2-AP; Fri, 18 Jun 2021 11:19:19 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.94.2 #2 (Red Hat Linux)) id 1luCWo-00DrQ0-Oi for linux-arm-kernel@lists.infradead.org; Fri, 18 Jun 2021 11:19:16 +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 AF4DF13A1; Fri, 18 Jun 2021 04:19:12 -0700 (PDT) Received: from [10.57.9.136] (unknown [10.57.9.136]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 05C003F719; Fri, 18 Jun 2021 04:19:09 -0700 (PDT) Subject: Re: [PATCH v4 5/6] iommu/dma: Simplify calls to iommu_setup_dma_ops() To: Jean-Philippe Brucker Cc: rjw@rjwysocki.net, lenb@kernel.org, joro@8bytes.org, mst@redhat.com, will@kernel.org, catalin.marinas@arm.com, baolu.lu@linux.intel.com, dwmw2@infradead.org, linux-acpi@vger.kernel.org, iommu@lists.linux-foundation.org, virtualization@lists.linux-foundation.org, linux-arm-kernel@lists.infradead.org, eric.auger@redhat.com, sebastien.boeuf@intel.com, kevin.tian@intel.com, lorenzo.pieralisi@arm.com, guohanjun@huawei.com, sudeep.holla@arm.com References: <20210610075130.67517-1-jean-philippe@linaro.org> <20210610075130.67517-6-jean-philippe@linaro.org> <6ce5fecb-fc81-5bf1-3577-6a09437b243e@arm.com> From: Robin Murphy Message-ID: Date: Fri, 18 Jun 2021 12:19:02 +0100 User-Agent: Mozilla/5.0 (Windows NT 10.0; rv:78.0) Gecko/20100101 Thunderbird/78.10.1 MIME-Version: 1.0 In-Reply-To: Content-Language: en-GB X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210618_041914_963658_F65D19DA X-CRM114-Status: GOOD ( 26.45 ) 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: , Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 2021-06-18 11:50, Jean-Philippe Brucker wrote: > On Wed, Jun 16, 2021 at 06:02:39PM +0100, Robin Murphy wrote: >>> diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c >>> index c62e19bed302..175f8eaeb5b3 100644 >>> --- a/drivers/iommu/dma-iommu.c >>> +++ b/drivers/iommu/dma-iommu.c >>> @@ -1322,7 +1322,9 @@ void iommu_setup_dma_ops(struct device *dev, u64 dma_base, u64 dma_limit) >>> if (domain->type == IOMMU_DOMAIN_DMA) { >>> if (iommu_dma_init_domain(domain, dma_base, dma_limit, dev)) >>> goto out_err; >>> - dev->dma_ops = &iommu_dma_ops; >>> + set_dma_ops(dev, &iommu_dma_ops); >>> + } else { >>> + set_dma_ops(dev, NULL); >> >> I'm not keen on moving this here, since iommu-dma only knows that its own >> ops are right for devices it *is* managing; it can't assume any particular >> ops are appropriate for devices it isn't. The idea here is that >> arch_setup_dma_ops() may have already set the appropriate ops for the >> non-IOMMU case, so if the default domain type is passthrough then we leave >> those in place. >> >> For example, I do still plan to revisit my conversion of arch/arm someday, >> at which point I'd have to undo this for that reason. > > Makes sense, I'll remove this bit. > >> Simplifying the base and size arguments is of course fine, but TBH I'd say >> rip the whole bloody lot out of the arch_setup_dma_ops() flow now. It's a >> considerable faff passing them around for nothing but a tenuous sanity check >> in iommu_dma_init_domain(), and now that dev->dma_range_map is a common >> thing we should expect that to give us any relevant limitations if we even >> still care. > > So I started working on this but it gets too bulky for a preparatory > patch. Dropping the parameters from arch_setup_dma_ops() seems especially > complicated because arm32 does need the size parameter for IOMMU mappings > and that value falls back to the bus DMA mask or U32_MAX in the absence of > dma-ranges. I could try to dig into this for a separate series. > > Even only dropping the parameters from iommu_setup_dma_ops() isn't > completely trivial (8 files changed, 55 insertions(+), 36 deletions(-) > because we still need the lower IOVA limit from dma_range_map), so I'd > rather send it separately and have it sit in -next for a while. Oh, sure, I didn't mean to imply that the whole cleanup should be within the scope of this series, just that we can shave off as much as we *do* need to touch here (which TBH is pretty much what you're doing already), and mainly to start taking the attitude that these arguments are now superseded and increasingly vestigial. I expected the cross-arch cleanup to be a bit fiddly, but I'd forgotten that arch/arm was still actively using these values, so maybe I can revisit this when I pick up my iommu-dma conversion again (I swear it's not dead, just resting!) Cheers, Robin. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel