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

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Tue, Aug 07, 2018 at 08:45:07AM -0600, Tamas K Lengyel wrote:
> On Tue, Aug 7, 2018 at 8:37 AM Roger Pau Monné <roger.pau@xxxxxxxxxx> wrote:
> >
> > On Tue, Aug 07, 2018 at 08:29:49AM -0600, Tamas K Lengyel wrote:
> > > 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
> >
> > Is the gmfn always the same (0x4625f3a)?
> >
> > > (XEN)     root_entry[00] = 273a18001
> > > (XEN)     context[10] = 2_27ba35001
> > > (XEN)     l4[000] = 9c0000027ba34107
> > > (XEN)     l3[118] = 8000000000000000
> > > (XEN)     l3[118] not present
> >
> > Can you also paste the full xl dmesg log? I'm specially interested in
> > the memory map of the machine which is printed quite early during Xen
> > boot.
> >
> 
> Unfortunately I don't have serial access on this laptop and "xl dmesg"
> gets completely filled with that error so the beginning of the log is
> lost by the time I get a terminal in dom0.

You can get the memory map while booting in PV mode, it's going to be
exactly the same regardless of whether Dom0 is PV or PVH.

> I'll try it on another
> laptop later today for which I have serial access. Across reboots the
> gmfn changes:
> 
> (XEN) [VT-D]DMAR:[DMA Read] Request device [0000:00:02.0] fault addr
> 23c251000, 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 23c251
> (XEN)     root_entry[00] = 273a18001
> (XEN)     context[10] = 2_27ba35001
> (XEN)     l4[000] = 9c0000027ba34107
> (XEN)     l3[008] = 8000000000000000
> (XEN)     l3[008] not present
> 

Thanks, Roger.

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