Quoting Joerg Roedel (2019-01-22 13:01:09) > Hi Daniel, > > On Tue, Jan 22, 2019 at 11:46:39AM +0100, Daniel Vetter wrote: > > Note that the string of platforms which have various issues with iommu > > and igfx is very long, thus far we only disabled it where there's no > > workaround to stop it from hanging the box, but otherwise left it > > enabled. So if we make a policy change to also disable it anywhere > > where it doesn't work well (instead of not at all), there's a pile > > more platforms to switch. > > I think its best to just disable iommu for the igfx devices on these > platforms. Can you pick up Eric's patch and extend it with the list of > affected platforms? We've been discussing this again more actively since a few months ago, and the discussion is still ongoing internally. According to our IOMMU folks there exists some desire to be able to assign the iGFX device aka have intel_iommu=on instead of intel_iommu=igfx_off due to how the devices might be grouped in IOMMU groups. Even when you would not be using the iGFX device. So for some uses, the fact that the device (group) is assignable seems to be more important than the iGFX device to be working. I'm afraid that retroactively disabling the assignment for such an old platform might break those usage scenarios. By my quick reading of the code, there's no way for user to turn the iGFX DMAR on once the quirk disables it. I guess one solution would be to default to intel_iommu=igfx_off for platforms that are older than certain threshold. But still allow user to enable. But that then requires duplicating the PCI ID database into iommu code. I don't really have winning moves to present, but I'm open to hearing how we can avoid more damage than starting to default to intel_iommu=on did already. Regards, Joonas > > Thanks, > > Joerg _______________________________________________ Intel-gfx mailing list Intel-gfx@xxxxxxxxxxxxxxxxxxxxx https://lists.freedesktop.org/mailman/listinfo/intel-gfx
