Re: [Xen-devel] [PATCH v3 0/4] x86/iommu: PVH Dom0 workarounds for missing RMRR entries

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Tue, Aug 7, 2018 at 8:04 AM Roger Pau Monne <roger.pau@xxxxxxxxxx> wrote:
>
> Hello,
>
> The following series implement a workaround for missing RMRR
> entries for a PVH Dom0. It's based on the iommu_inclusive_mapping VTd
> option.
>
> The PVH workaround identity maps all regions marked as reserved in the
> memory map.
>
> Note that this workaround is enabled by default on Intel hardware. It's
> also available to AMD hardware, although it's disabled by default in
> that case.
>
> The series can be found at:
>
> git://xenbits.xen.org/people/royger/xen.git iommu_inclusive_v3
>
> Thanks, Roger.
> Roger Pau Monne (4):
>   iommu: introduce dom0-iommu option
>   iommu: make iommu_inclusive_mapping a suboption of dom0-iommu
>   dom0/pvh: change the order of the MMCFG initialization
>   x86/iommu: add reserved dom0-iommu option to map reserved memory
>     ranges
>
>  docs/misc/xen-command-line.markdown         | 47 +++++++++++
>  xen/arch/x86/hvm/dom0_build.c               |  9 ++-
>  xen/arch/x86/hvm/io.c                       |  5 ++
>  xen/arch/x86/x86_64/mm.c                    |  3 +-
>  xen/drivers/passthrough/amd/iommu_init.c    |  2 +-
>  xen/drivers/passthrough/amd/pci_amd_iommu.c | 11 ++-
>  xen/drivers/passthrough/arm/iommu.c         |  4 +
>  xen/drivers/passthrough/iommu.c             | 62 +++++++++++++--
>  xen/drivers/passthrough/vtd/extern.h        |  2 -
>  xen/drivers/passthrough/vtd/iommu.c         | 25 +++---
>  xen/drivers/passthrough/vtd/x86/vtd.c       | 58 +-------------
>  xen/drivers/passthrough/x86/iommu.c         | 87 +++++++++++++++++++++
>  xen/include/asm-x86/hvm/io.h                |  3 +
>  xen/include/xen/iommu.h                     |  8 +-
>  14 files changed, 240 insertions(+), 86 deletions(-)
>
> --

Hi Roger,
I gave this branch a spin on a Dell XPS laptop booting UEFI with Linux
4.18-rc8. I was able to get dom0 to boot with PVH but the physical
keyboard of the laptop stopped working, it works no problem with just
Linux 4.18-rc8 or PV dom0, so I had to plug in a USB keyboard. After
running for a minute or two the system starts to slow down to the
point where it becomes unresponsive. The xl dmesg log is filled with
this error:

(XEN) [VT-D]iommu.c:919: iommu_fault_status: Fault Overflow
(XEN) [VT-D]iommu.c:921: iommu_fault_status: Primary Pending Fault
(XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
4625f3a000, iommu reg = ffff82c00181c000
(XEN) [VT-D]DMAR: reason 06 - PTE Read access is not set
(XEN) print_vtd_entries: iommu #0 dev 0000:00:02.0 gmfn 4625f3a
(XEN)     root_entry[00] = 273a18001
(XEN)     context[10] = 2_27ba35001
(XEN)     l4[000] = 9c0000027ba34107
(XEN)     l3[118] = 8000000000000000
(XEN)     l3[118] not present

The device in question is:

00:02.0 VGA compatible controller: Intel Corporation HD Graphics 620
(rev 02) (prog-if 00 [VGA controller])
    Subsystem: Dell HD Graphics 620
    Control: I/O+ Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop-
ParErr- Stepping- SERR- FastB2B- DisINTx+
    Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
    Latency: 0
    Interrupt: pin A routed to IRQ 144
    Region 0: Memory at db000000 (64-bit, non-prefetchable) [size=16M]
    Region 2: Memory at 90000000 (64-bit, prefetchable) [size=256M]
    Region 4: I/O ports at f000 [size=64]
    [virtual] Expansion ROM at 000c0000 [disabled] [size=128K]
    Capabilities: [40] Vendor Specific Information: Len=0c <?>
    Capabilities: [70] Express (v2) Root Complex Integrated Endpoint, MSI 00
        DevCap:    MaxPayload 128 bytes, PhantFunc 0
            ExtTag- RBE+
        DevCtl:    Report errors: Correctable- Non-Fatal- Fatal- Unsupported-
            RlxdOrd- ExtTag- PhantFunc- AuxPwr- NoSnoop-
            MaxPayload 128 bytes, MaxReadReq 128 bytes
        DevSta:    CorrErr- UncorrErr- FatalErr- UnsuppReq- AuxPwr- TransPend-
        DevCap2: Completion Timeout: Not Supported, TimeoutDis-, LTR-,
OBFF Not Supported
        DevCtl2: Completion Timeout: 50us to 50ms, TimeoutDis-, LTR-,
OBFF Disabled
    Capabilities: [ac] MSI: Enable+ Count=1/1 Maskable- 64bit-
        Address: fee00000  Data: 4028
    Capabilities: [d0] Power Management version 2
        Flags: PMEClk- DSI+ D1- D2- AuxCurrent=0mA
PME(D0-,D1-,D2-,D3hot-,D3cold-)
        Status: D0 NoSoftRst- PME-Enable- DSel=0 DScale=0 PME-
    Capabilities: [100 v1] Process Address Space ID (PASID)
        PASIDCap: Exec- Priv-, Max PASID Width: 14
        PASIDCtl: Enable- Exec- Priv-
    Capabilities: [200 v1] Address Translation Service (ATS)
        ATSCap:    Invalidate Queue Depth: 00
        ATSCtl:    Enable-, Smallest Translation Unit: 00
    Capabilities: [300 v1] Page Request Interface (PRI)
        PRICtl: Enable- Reset-
        PRISta: RF- UPRGI- Stopped+
        Page Request Capacity: 00008000, Page Request Allocation: 00000000
    Kernel driver in use: i915
    Kernel modules: i915

The error is similar to one I reported in 2015
(https://lists.xenproject.org/archives/html/xen-devel/2015-08/msg02339.html)
but that was due to AMT being enabled on the system, while this laptop
doesn't have AMT enabled. The boot params I had for Xen: loglvl=all
guest_loglvl=all dom0_mem=4096M,max:4096M dom0_max_vcpus=2 sched=null
dom0=pvh iommu=required,debug dom0-iommu=relaxed console=vga

Let us know if we can provide any additional information.

Thanks,
Tamas

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