On Mon, 2015-04-27 at 09:39 -0600, Alex Williamson wrote: > David, > > Since this got pulled anyway, do you plan to follow-up with patches to > limit the graphics RMRR exception to the known and acceptable uses and > document them, or should I send a revert patch? I don't think what we > have here is acceptable going forward or being backported to stable. > Thanks,
I didn't plan to, no. So far we *only* know of acceptable uses of RMRR on graphics devices, and the false positives that Linda mentioned. The only cases we ever saw of RMRR being *problematic* when we tried to assign devices to guests were non-graphics devices, weren't they? Although obviously I'm looking into the oops that sl4ever reported; currently I'm wondering if that was broken even before your patch that blacklisted all RMRR-afflicted devices. It looks like device_to_iommu() doesn't return the correct results for devices behind a disabled IOMMU; it incorrectly attributes them to a catch-all IOMMU instead. Or perhaps this is probably tied into the fact that your patch broke iommu=pt for RMRR-afflicted devices too. They currently get full translation. Which surely shouldn't be necessary, since passthrough mode would obviously *also* preserve the RMRR regions of 1:1 mappings. -- dwmw2
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