On Thu, Feb 02, 2017 at 01:34:03PM +0000, Robin Murphy wrote: > On 02/02/17 11:26, Will Deacon wrote: > > On Wed, Feb 01, 2017 at 09:19:22PM +0200, Michael S. Tsirkin wrote: > >> On Wed, Feb 01, 2017 at 06:27:09PM +0000, Will Deacon wrote: > >>> On Wed, Feb 01, 2017 at 08:09:21PM +0200, Michael S. Tsirkin wrote: > >>>> I'd like to do that instead. It's fastboot doing the unreasonable thing > >>>> here and deviating from what every other legacy device without exception > >>>> did for years. If this means fastboot will need to update to virtio 1, > >>>> all the better. > >>> > >>> The problem still exists with virtio 1, unless we require that the > >>> "dma-coherent" property is set/unset correctly when VIRTIO_F_IOMMU_PLATFORM > >>> is advertised by the device (which is what I suggested in my reply). > >> > >> I'm not ignoring that, but I need to understand that part a bit better. > >> I'll reply to that patch in a day or two after looking at how _CCA is > >> supposed to work. > > > > Thanks. I do think that whatever solution we come up with for virtio 1 > > should influence what we do for legacy. > > > >>> We can't detect the fastmodel, > >> > >> Surely, it puts a hardware id somewhere? I think you mean > >> fastmodel isn't always affected, right? > > > > I don't think there's a hardware ID. The thing is, the fastmodel is a > > toolkit for building all sorts of platforms: you can chop and change > > the CPUs, the peripherals, the memory, the interrupt controller, the > > interconnect etc. Pretty much everything can be customised. So, for > > any fastmodel configuration that places virtio upstream of the SMMU > > (which is common, because virtio is one of the few DMA-capable peripherals > > that the fastmodel supports), we need to do something special. > > > >> I'd like to see basically > >> > >> if (fastmodel) > >> a pile of special work-arounds > >> else > >> not less hacky but more common virtio work-arounds > >> > >> :) > >> > >> And then I can apply whatever comes from @arm.com and not > >> worry about breaking actual hardware. > > > > What we could do is call iommu_group_get(&vdev->dev) for legacy > > Actually, that should be vdev->dev.parent - I'm now not sure quite what > I managed to successfully test yesterday, but apparently it wasn't this > patch :( > > > devices if CONFIG_ARM64. If that returns non-NULL, then we know that > > the device is upstream of an SMMU, which means it must be the fastmodel. > > We can boot 32-bit kernels on models, so I'd be inclined to keep > CONFIG_ARM included, but I do tend to agree that explicitly checking for > an IOMMU is probably the cleanest approach if we reposition this as a > more specific quirk. I'll split apart the "Fast Models are wacky" vs. > "uh-oh device coherency" aspects and spin a v2 so that we can > (hopefully) sort the regression out ASAP. > > Robin. I am inclined to say, for 4.10 let's revert c7070619f3408d9a0dffbed9149e6f00479cf43b since what it fixes is not a regression in 4.10. So I think we can defer the fix to 4.11. I think we still want f7f6634d23830ff74335734fbdb28ea109c1f349 for hosts with virtio 1 support. All this will hopefully push hosts to just implement virtio 1. For mmio the changes are very small: several new registers, that's all. You want this for proper 64 bit dma mask anyway. > > > > Will > > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
