> -----Original Message----- > From: iommu-boun...@lists.linux-foundation.org [mailto:iommu- > boun...@lists.linux-foundation.org] On Behalf Of Andreas Herrmann > Sent: Friday, January 24, 2014 1:27 AM > To: Sethi Varun-B16395 > Cc: Andreas Herrmann; iommu@lists.linux-foundation.org; Will Deacon; > linux-arm-ker...@lists.infradead.org > Subject: Re: [PATCH v3 02/11] iommu/arm-smmu: Introduce iommu_group > notifier block > > On Wed, Jan 22, 2014 at 07:07:40PM +0000, Varun Sethi wrote: > > > -----Original Message----- > > > From: Will Deacon [mailto:will.dea...@arm.com] > > > Sent: Wednesday, January 22, 2014 9:04 PM > > > To: Sethi Varun-B16395 > > > Cc: Andreas Herrmann; iommu@lists.linux-foundation.org; linux-arm- > > > ker...@lists.infradead.org; Andreas Herrmann > > > Subject: Re: [PATCH v3 02/11] iommu/arm-smmu: Introduce iommu_group > > > notifier block > > > > > > On Wed, Jan 22, 2014 at 01:54:11PM +0000, Varun Sethi wrote: > > > > > > > Ok, so are you suggesting that we perform the isolation > > > > > > > mapping in arm_smmu_add_device and drop the notifier > altogether? > > > > > > I think that should be fine, until we want to delay mapping > > > > > > creation till driver bind time. > > > > > > > > > > Is there a hard dependency on that? > > > > > > > > > Not sure, may be Andreas can answer that. > > > > > > Ok. Andreas? I would have thought doing this *earlier* shouldn't be > > > a problem (the DMA ops must be swizzled before the driver is probed). > > > > > > > > > But the "isolate device" property should dictate iommu group > > > creation. > > > > > > > > > > The reason we added automatic group creation (per-device) is for > > > > > VFIO, which expects all devices to be in a group regardless of > > > > > the device isolation configuration. > > > > > > > > > IIUC, with the "isolate devices" property we ensure that there > > > > would be independent SMR and S2CR per device. Is that correct? > > > > > > Yes, as part of giving them independent sets of page tables. > > > Initially these tables don't have any valid mappings, but the > > > dma-mapping API will populate them in response to > dma_map_*/dma_alloc/etc. > > > > > > Not sure what this has to do with us putting devices into their own > > > groups... > > > [Sethi Varun-B16395] Devices in an iommu group would share the dma > > mapping, so shouldn't they be sharing the SMR and context registers? > > I aggree with the context but SMRs won't be shared. I think you just can > say that a certain subset of the available SMRs will be used to map all > devices in an iommu group to the same context. Depending on what > streamIDs each device has you might have to use separate SMRs for each > device to map it to the same context. [Sethi Varun-B16395] IIUC the SMRs would unique per device, but there is a possibility where the number of context registers are restricted? In that case IOMMU groups should correspond to unique stream IDs (and corresponding SMRs).
> > > In case of the "isolate devices" property, each device would have its > > own SMR and context registers, thus allowing the devices to have > > independent mappings and allowing them to fall in separate iommu > > groups. > > I aggree with Varun's view here. (Now that I take iommu groups into > consideration.) > > But my goal with the "isolate devices" thing was twofold: > > 1. actual make use of SMMU for address translation for all master > devices (instead of just bypassing the SMMU) [Sethi Varun-B16395] even if masters have to share translation? But from the patch it seemed that we are creating mapping only if we find the isolate devices property. > > plus > > 2. put each master into it's own domain to isolate it > > The latter matches usage of separate iommu groups for devices. If we now > use the isolate devices property to just control whether master devices > fall into the same or separate iommu groups it seems to me we would need > to have another mechanism that triggers the creation of a mapping for a > group. > > What do you think? > [Sethi Varun-B16395] As mentioned before, we should be having iommu group per device (having a unique stream id). Isolate devices property just ensures that each device has a unique context. Now, for the devices for which we don't have the isolate device property, can't we have the multiple devices point to a common mapping. -Varun _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu