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Re: i915 dma faults on Xen

On 21.10.2020 11:58, Roger Pau Monné wrote:
> On Fri, Oct 16, 2020 at 12:23:22PM -0400, Jason Andryuk wrote:
>> The RMRRs are:
>> (XEN) [VT-D]Host address width 39
>> (XEN) [VT-D]found ACPI_DMAR_DRHD:
>> (XEN) [VT-D]  dmaru->address = fed90000
>> (XEN) [VT-D]drhd->address = fed90000 iommu->reg = ffff82c00021d000
>> (XEN) [VT-D]cap = 1c0000c40660462 ecap = 19e2ff0505e
>> (XEN) [VT-D] endpoint: 0000:00:02.0
>> (XEN) [VT-D]found ACPI_DMAR_DRHD:
>> (XEN) [VT-D]  dmaru->address = fed91000
>> (XEN) [VT-D]drhd->address = fed91000 iommu->reg = ffff82c00021f000
>> (XEN) [VT-D]cap = d2008c40660462 ecap = f050da
>> (XEN) [VT-D] IOAPIC: 0000:00:1e.7
>> (XEN) [VT-D] MSI HPET: 0000:00:1e.6
>> (XEN) [VT-D]  flags: INCLUDE_ALL
>> (XEN) [VT-D]found ACPI_DMAR_RMRR:
>> (XEN) [VT-D] endpoint: 0000:00:14.0
>> (XEN) [VT-D]dmar.c:615:   RMRR region: base_addr 78863000 end_addr 78882fff
>> (XEN) [VT-D]found ACPI_DMAR_RMRR:
>> (XEN) [VT-D] endpoint: 0000:00:02.0
>> (XEN) [VT-D]dmar.c:615:   RMRR region: base_addr 7d000000 end_addr 7f7fffff
>> (XEN) [VT-D]found ACPI_DMAR_RMRR:
>> (XEN) [VT-D] endpoint: 0000:00:16.7
>> (XEN) [VT-D]dmar.c:581:  Non-existent device (0000:00:16.7) is
>> reported in RMRR (78907000, 78986fff)'s scope!
>> (XEN) [VT-D]dmar.c:596:   Ignore the RMRR (78907000, 78986fff) due to
> This is also part of a reserved region, so should be added to the
> iommu page tables anyway regardless of this message.

Could you clarify why you think so? RMRRs are tied to devices, so
if a device in reality doesn't exist (and no other one uses the
same range), I don't see why an IOMMU mapping would be needed
(unless to work around some related firmware bug). Plus aiui none
of the IOMMU faults actually report this range as having got




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