Re: [Xen-devel] IOMMU fault with IGD passthrough setup on XEN 4.8.0

["G.R." <firemeteor@xxxxxxxxxxxxxxxxxxxxx>]

On Fri, Jan 20, 2017 at 12:30 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>> On 17.01.17 at 16:08, <firemeteor@xxxxxxxxxxxxxxxxxxxxx> wrote:
>> But fortunately commenting out that line could still reproduce the IOMMU
>> fault.
>> I was lucky to capture the full log before it fills up my 100MB ring buffer
>> (in less than 2 seconds).
>
> So here's a first take at a debugging patch. I've tried to limit existing
> output, so that you'd have better chance of again capturing all
> interesting messages.
>

Hi Jan,
I finally get some spare time to collect the debug info.
Please find the full log in the attachment.

The mapping appears to be working:
(XEN) d8: RMRR [cf800,dfa00] mapped cf800
(XEN) d8: RMRR [cf800,dfa00] mapped cf900
(XEN) d8: RMRR [cf800,dfa00] mapped cfb00
(XEN) d8: RMRR [cf800,dfa00] mapped cff00
(XEN) d8: RMRR [cf800,dfa00] mapped d0700
(XEN) d8: RMRR [cf800,dfa00] mapped d1700
(XEN) d8: RMRR [cf800,dfa00] mapped d3700
(XEN) d8: RMRR [cf800,dfa00] mapped d7700
(XEN) d8: RMRR [cf800,dfa00] mapped df700
(XEN) d8: RMRR [cf800,dfa00] alloc -> ffff83013156ffb0

But I'm not sure if the vtd_entries look correct: (Is the 'not
present' line okay?)
(XEN) d8: RMRR [cf800,dfa00] mapped cfb00
(XEN) print_vtd_entries: iommu ffff8304152ec600 dev 0000:00:02.0 gmfn cfb00
(XEN)     root_entry = ffff820040056000
(XEN)     root_entry[0] = 201fc6001
(XEN)     context = ffff820040020000
(XEN)     context[10] = 1_13956c001
(XEN)     l3 = ffff820040022000
(XEN)     l3_index = 3
(XEN)     l3[3] = 1394ec003
(XEN)     l2 = ffff820040023000
(XEN)     l2_index = 7d
(XEN)     l2[7d] = 0
(XEN)     l2[7d] not present

Still see the 'Fault overflow' line in the very first fault.
The fault is about write-access not permitted.
Is the map read-only here? Or are we looking at the correct PTE?
(XEN) [VT-D]iommu.c:924: iommu_fault_status: Fault Overflow
(XEN) [VT-D]iommu.c:926: iommu_fault_status: Primary Pending Fault
(XEN) [VT-D]DMAR:[DMA Write] Request device [0000:00:02.0] fault addr
cfa00000, iommu reg = ffff82c000201000
(XEN) [VT-D]DMAR: reason 05 - PTE Write access is not set
(XEN) print_vtd_entries: iommu ffff8304152ec600 dev 0000:00:02.0 gmfn cfa00
(XEN)     root_entry = ffff8304152e9000
(XEN)     root_entry[0] = 201fc6001
(XEN)     context = ffff830201fc6000
(XEN)     context[10] = 1_13956c001
(XEN)     l3 = ffff83013956c000
(XEN)     l3_index = 3
(XEN)     l3[3] = 1394ec003
(XEN)     l2 = ffff8301394ec000
(XEN)     l2_index = 7d
(XEN)     l2[7d] = 0
(XEN)     l2[7d] not present

> Jan
>

Attachment: dmesg.xz
Description: application/xz

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