> -----Original Message----- > From: Alex Williamson [mailto:alex.williamson@xxxxxxxxxx] > Sent: 05 June 2018 18:03 > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@xxxxxxxxxx> > Cc: eric.auger@xxxxxxxxxx; pmorel@xxxxxxxxxxxxxxxxxx; > kvm@xxxxxxxxxxxxxxx; linux-kernel@xxxxxxxxxxxxxxx; iommu@lists.linux- > foundation.org; Linuxarm <linuxarm@xxxxxxxxxx>; John Garry > <john.garry@xxxxxxxxxx>; xuwei (O) <xuwei5@xxxxxxxxxx>; Joerg Roedel > <joro@xxxxxxxxxx>; David Woodhouse <dwmw2@xxxxxxxxxxxxx> > Subject: Re: [PATCH v6 0/7] vfio/type1: Add support for valid iova list > management > > [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. Ah..:(. This looks similar to the pci window range reporting issue faced in the arm world. I see the RFC you have sent out to ignore these "known" RMRRs. Hope we will be able to resolve this soon. Thanks, Shameer > 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
