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. I will revert the changes in 722ec35f7 and fold them in the new version along with Robin's suggestions. Thanks, Lorenzo > > > Best regards > Marek Szyprowski, PhD > Samsung R&D Institute Poland > > > > >On 07/06/16 14:30, Lorenzo Pieralisi wrote: > >>Current bus notifier in ARM64 (__iommu_attach_notifier) > >>attempts to attach dma_ops to a device on BUS_NOTIFY_ADD_DEVICE > >>action notification. > >> > >>This causes issues on ACPI based systems, where PCI devices > >>can be added before the IOMMUs the devices are attached to > >>had a chance to be probed, causing failures on attempts to > >>attach dma_ops in that the domain for the respective IOMMU > >>may not be set-up yet by the time the bus notifier is run. > >> > >>Devices dma_ops do not require to be set-up till the matching > >>device drivers are probed. This means that instead of running > >>the notifier attaching dma_ops to devices (__iommu_attach_notifier) > >>on BUS_NOTIFY_ADD_DEVICE action, it can be run just before the > >>device driver is bound to the device in question (on action > >>BUS_NOTIFY_BIND_DRIVER) so that it is certain that its IOMMU > >>group and domain are set-up accordingly at the time the > >>notifier is triggered. > >> > >>This patch changes the notifier action upon which dma_ops > >>are attached to devices and defer it to driver binding time, > >>so that IOMMU devices have a chance to be probed and to register > >>their bus notifiers before the dma_ops attach sequence for a > >>device is actually carried out. > >> > >>Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@xxxxxxx> > >>Cc: Will Deacon <will.deacon@xxxxxxx> > >>Cc: Catalin Marinas <catalin.marinas@xxxxxxx> > >>Cc: Robin Murphy <robin.murphy@xxxxxxx> > >>--- > >> arch/arm64/mm/dma-mapping.c | 2 +- > >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> > >>diff --git a/arch/arm64/mm/dma-mapping.c b/arch/arm64/mm/dma-mapping.c > >>index c566ec8..79b0882 100644 > >>--- a/arch/arm64/mm/dma-mapping.c > >>+++ b/arch/arm64/mm/dma-mapping.c > >>@@ -848,7 +848,7 @@ static int __iommu_attach_notifier(struct > >>notifier_block *nb, > >> { > >> struct iommu_dma_notifier_data *master, *tmp; > >> > >>- if (action != BUS_NOTIFY_ADD_DEVICE) > >>+ if (action != BUS_NOTIFY_BIND_DRIVER) > > > >With this, you can also get rid of the priority setting and big > >fat explanatory comment in register_iommu_dma_ops_notifier(). > > > >Robin. > > > >> return 0; > >> > >> mutex_lock(&iommu_dma_notifier_lock); > >> > > > > > > > -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
