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Date: Thu, 23 Jun 2016 08:13:30 +0200 From: Marek Szyprowski <m.szyprowski@...sung.com> To: Lorenzo Pieralisi <lorenzo.pieralisi@....com> Cc: Robin Murphy <robin.murphy@....com>, iommu@...ts.linux-foundation.org, linux-arm-kernel@...ts.infradead.org, "Rafael J. Wysocki" <rjw@...ysocki.net>, Marc Zyngier <marc.zyngier@....com>, Catalin Marinas <catalin.marinas@....com>, Joerg Roedel <joro@...tes.org>, Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org, linux-pci@...r.kernel.org, Sinan Kaya <okaya@...eaurora.org>, linux-acpi@...r.kernel.org, Hanjun Guo <hanjun.guo@...aro.org>, Tomasz Nowicki <tn@...ihalf.com>, Jon Masters <jcm@...hat.com> Subject: Re: [RFC PATCH v2 03/15] arm64: mm: change IOMMU notifier action to attach DMA ops Hi Lorenzo, On 2016-06-21 18:06, Lorenzo Pieralisi wrote: > Hi Marek, > > On Tue, Jun 21, 2016 at 09:53:20AM +0200, Marek Szyprowski wrote: >> Hi Robin, >> >> >> On 2016-06-17 11:27, Robin Murphy wrote: >>> Hi Lorenzo, >>> >>> I think this patch makes sense even independent of the rest of the >>> series, one nit inline notwithstanding. >>> >>> Marek; I'm curious as to whether this could make the workaround in >>> 722ec35f7 obsolete as well, or are all the drivers also bound >>> super-early in the setup you had there? >> Yes, this will solve that problem too. I will also hide some possible >> deferred probe issues, because the moment at which IOMMU is activated >> will be postponed. The only drawback with this approach is the fact >> that is drivers won't be allowed to do any dma-mapping operations on >> devices, which they don't own. This should not be a big issue, but >> this was the reason to setup IOMMU on device add instead of driver >> bind. >> >> While at it, please make sure that the case of failed client driver >> probe will be handled properly. IOMMU might do some operations while >> setting up and if the client driver fails to probe (for whatever >> reason, might be a deferred probe too), those operation has to be >> undone. However the current code of the driver core won't call any >> notifier (like BUS_NOTIFY_UNBOUND_DRIVER or whatever else) in such >> case. > Isn't Andy's commit 14b6257a5f3d enough ? Is that what you had in > mind ? > >> Long time ago I used BUS_NOTIFY_BIND_DRIVER based approach for my >> Exynos IOMMU patches and had to extend bus core with such patch: >> https://patchwork.kernel.org/patch/4678181/ to properly cleanup >> after failed client driver probe and avoid leaking resources. Please >> read the discussion, because some changes were requested to it. > It looks like commit 14b6257a5f3d ("device core: add > BUS_NOTIFY_DRIVER_NOT_BOUND notification") does what you > are requesting, please let me know if that's enough. Yes, that's exactly the change I needed that time. Nice to see that it finally landed in mainline. > I will revert the changes in 722ec35f7 and fold them in the > new version along with Robin's suggestions. Okay. Best regards -- Marek Szyprowski, PhD Samsung R&D Institute Poland
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