[Cc +dwmw2] On Fri, 25 May 2018 14:54:08 -0600 Alex Williamson <alex.williamson@xxxxxxxxxx> wrote: > On Fri, 25 May 2018 08:45:36 +0000 > Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> wrote: > > > Yes, the above changes related to list empty cases looks fine to me. > > Thanks Shameer, applied to my next branch with the discussed fixes for > v4.18 (modulo patch 4/7 which Joerg already pushed for v4.17). Thanks, Hi Shameer, We're still hitting issues with this. VT-d marks reserved regions for any RMRR ranges, which are IOVA ranges that the BIOS requests to be identity mapped for a device. These are indicated by these sorts of log entries on boot: DMAR: Setting RMRR: DMAR: Setting identity map for device 0000:00:02.0 [0xbf800000 - 0xcf9fffff] DMAR: Setting identity map for device 0000:00:1a.0 [0xbe8d1000 - 0xbe8dffff] DMAR: Setting identity map for device 0000:00:1d.0 [0xbe8d1000 - 0xbe8dffff] So while for an unaffected device, I see very usable ranges for QEMU, such as: 00: 0000000000000000 - 00000000fedfffff 01: 00000000fef00000 - 01ffffffffffffff If I try to assign the previously assignable 00:02.0 IGD graphics device, I get: 00: 0000000000000000 - 00000000bf7fffff 01: 00000000cfa00000 - 00000000fedfffff 02: 00000000fef00000 - 01ffffffffffffff And we get a fault when QEMU tries the following mapping: vfio_dma_map(0x55f790421a20, 0x100000, 0xbff00000, 0x7ff163f00000) bff00000 clearly extends into the gap starting at bf800000. VT-d is rather split-brained about RMRRs, typically we'd exclude devices from assignment at all for relying on RMRRs and these reserved ranges would be a welcome mechanism to avoid conflicts with those ranges, but for RMRR ranges covering IGD and USB devices we've decided that we don't need to honor the RMRR (see device_is_rmrr_locked()), but it's still listed as a reserved range and bites us here. Unless we can get VT-d to exclude RMRRs from reserved regions where we've already seen fit to allow the devices to participate in the IOMMU API, this would introduce a functional regression for assignment of these devices. David, should we skip GFX and USB devices with RMRRs in intel_iommu_get_resv_regions() just as we do in device_is_rmrr_locked()? Thanks, Alex
