[Bug 1920013] [NEW] Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[Bug 1920013] [NEW] Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[cyrozap]

Public bug reported:

Attempting to pass through a PCIe device from a ppc64le host to an
x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
fails with the following error:

    include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00 is
not an instance of type qemu:iommu-memory-region

To reproduce this issue, simply run the following command on a POWER9
system:

    qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

Where $DBSF is a domain:bus:slot.function PCIe device address.

This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
has never worked. Helpfully, the error message it prints seems to
indicate where the problem is:

    hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510 is
not an instance of type qemu:iommu-memory-region

My kernel (Linux v5.8.0 plus some small unrelated patches) is built with
the page size set to 4k, so this issue shouldn't be due to a page size
mismatch. And as I stated earlier, my host arch is ppc64le, so it
shouldn't be an endianness issue, either.

I assume this should be possible (in theory) since I've seen reports of
others getting PCIe passthrough working with aarch64 guests on x86_64
hosts, but of course that (passthrough to weird guest arch on x86) is
somewhat the opposite of what I'm trying to do (passthrough to x86 on
weird host arch) so I don't know for sure. If it is possible, I'm
willing to develop a fix myself, but I'm almost completely unfamiliar
with QEMU's internals so if anyone has any advice on where to start I'd
greatly appreciate it.

** Affects: qemu
     Importance: Undecided
         Status: New


** Tags: ppc

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  New

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions

[Bug 1920013] Re: Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[cyrozap]

I've done some more investigating, and have produced a backtrace of the
error:

    #0  0x00003ffff6b63228 in __libc_signal_restore_set (set=0x3fffffffcec8) at ../sysdeps/unix/sysv/linux/internal-signals.h:84
    #1  0x00003ffff6b63228 in __GI_raise (sig=<optimized out>) at ../sysdeps/unix/sysv/linux/raise.c:48
    #2  0x00003ffff6b4358c in __GI_abort () at abort.c:79
    #3  0x000000010080d524 in object_dynamic_cast_assert
        (obj=0x1016db860, typename=0x100bf9980 "qemu:iommu-memory-region", file=0x100bf9940 "/usr/src/qemu/include/exec/memory.h", line=<optimized out>, func=0x100c08a70 <__func__.21845> "IOMMU_MEMORY_REGION") at ../qom/object.c:883
    #4  0x00000001006b6f84 in IOMMU_MEMORY_REGION (obj=<optimized out>) at /usr/src/qemu/include/exec/memory.h:42
    #5  0x00000001006b6f84 in vfio_spapr_create_window (container=0x102357380, section=0x3fffffffd410, pgsize=0x3fffffffd368)
        at ../hw/vfio/spapr.c:149
    #6  0x00000001007a09a0 in vfio_listener_region_add (listener=0x102357390, section=0x3fffffffd410) at ../hw/vfio/common.c:709
    #7  0x00000001006ea6f4 in listener_add_address_space (as=<optimized out>, listener=0x102357390) at ../softmmu/memory.c:2729
    #8  0x00000001006ea6f4 in memory_listener_register (listener=0x102357390, as=<optimized out>) at ../softmmu/memory.c:2796
    #9  0x00000001007a36f4 in vfio_connect_container (errp=0x3fffffffe818, as=<optimized out>, group=0x102357300)
        at ../hw/vfio/common.c:1886
    #10 0x00000001007a36f4 in vfio_get_group (groupid=<optimized out>, as=<optimized out>, errp=0x3fffffffe818)
        at ../hw/vfio/common.c:2003
    #11 0x000000010071a2a8 in vfio_realize (pdev=0x102350f80, errp=0x3fffffffe818) at ../hw/vfio/pci.c:2834
    #12 0x0000000100488e20 in pci_qdev_realize (qdev=0x102350f80, errp=0x3fffffffe940) at ../hw/pci/pci.c:2113
    #13 0x00000001008063e0 in device_set_realized (obj=0x102350f80, value=<optimized out>, errp=0x3fffffffea50) at ../hw/core/qdev.c:761
    #14 0x000000010080afbc in property_set_bool
        (obj=0x102350f80, v=<optimized out>, name=<optimized out>, opaque=0x1014f1930, errp=0x3fffffffea50) at ../qom/object.c:2257
    #15 0x000000010080ee2c in object_property_set (obj=0x102350f80, name=0x100c023a0 "realized", v=
        0x102351d30, errp=0x101450b30 <error_fatal>) at ../qom/object.c:1402
    #16 0x000000010080a55c in object_property_set_qobject
        (obj=0x102350f80, name=0x100c023a0 "realized", value=<optimized out>, errp=0x101450b30 <error_fatal>) at ../qom/qom-qobject.c:28
    #17 0x000000010080f1b0 in object_property_set_bool
        (obj=0x102350f80, name=0x100c023a0 "realized", value=<optimized out>, errp=0x101450b30 <error_fatal>) at ../qom/object.c:1472
    #18 0x00000001008042bc in qdev_realize (dev=0x102350f80, bus=<optimized out>, errp=0x101450b30 <error_fatal>)
        at ../hw/core/qdev.c:389
    #19 0x000000010036cfac in qdev_device_add (opts=0x1014e9960, errp=0x101450b30 <error_fatal>)
        at /usr/src/qemu/include/hw/qdev-core.h:17
    #20 0x00000001006d5e68 in device_init_func (opaque=<optimized out>, opts=<optimized out>, errp=<optimized out>)
        at ../softmmu/vl.c:1202
    #21 0x0000000100abe070 in qemu_opts_foreach
        (list=<optimized out>, func=0x1006d5e40 <device_init_func>, opaque=0x0, errp=0x101450b30 <error_fatal>)
        at ../util/qemu-option.c:1167
    #22 0x00000001006da110 in qemu_create_cli_devices () at ../softmmu/vl.c:2494
    #23 0x00000001006da110 in qmp_x_exit_preconfig (errp=<optimized out>) at ../softmmu/vl.c:2542
    #24 0x00000001006df87c in qemu_init (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at ../softmmu/vl.c:3553
    #25 0x000000010031d3c8 in main (argc=<optimized out>, argv=<optimized out>, envp=<optimized out>) at ../softmmu/main.c:49

I also took a look at some of the arguments in frame #5 (where the type
check is failing):

    (gdb) f
    #5  vfio_spapr_create_window (container=0x102357380, section=0x3fffffffd410, pgsize=0x3fffffffd368) at ../hw/vfio/spapr.c:149
    149         IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
    (gdb) l
    144     int vfio_spapr_create_window(VFIOContainer *container,
    145                                  MemoryRegionSection *section,
    146                                  hwaddr *pgsize)
    147     {
    148         int ret = 0;
    149         IOMMUMemoryRegion *iommu_mr = IOMMU_MEMORY_REGION(section->mr);
    150         uint64_t pagesize = memory_region_iommu_get_min_page_size(iommu_mr), pgmask;
    151         unsigned entries, bits_total, bits_per_level, max_levels;
    152         struct vfio_iommu_spapr_tce_create create = { .argsz = sizeof(create) };
    153         long rampagesize = qemu_minrampagesize();
    (gdb) p *section->mr
    $5 = {parent_obj = {class = 0x101512f90, free = 0x0, Python Exception <class 'gdb.error'> There is no member named keys.: 
    properties = 0x101716b60, ref = 1, parent = 0x1016db800}, romd_mode = true, 
      ram = true, subpage = false, readonly = false, nonvolatile = false, rom_device = false, flush_coalesced_mmio = false, 
      dirty_log_mask = 0 '\000', is_iommu = false, ram_block = 0x101725c30, owner = 0x1016db800, ops = 0x101300b00 <unassigned_mem_ops>, 
      opaque = 0x0, container = 0x0, size = 134217728, addr = 0, destructor = 0x1006e0d50 <memory_region_destructor_ram>, 
      align = 2097152, terminates = true, ram_device = false, enabled = true, warning_printed = false, vga_logging_count = 0 '\000', 
      alias = 0x0, alias_offset = 0, priority = 0, subregions = {tqh_first = 0x0, tqh_circ = {tql_next = 0x0, tql_prev = 0x1016db908}}, 
      subregions_link = {tqe_next = 0x0, tqe_circ = {tql_next = 0x0, tql_prev = 0x0}}, coalesced = {tqh_first = 0x0, tqh_circ = {
          tql_next = 0x0, tql_prev = 0x1016db928}}, name = 0x101725b10 "pc.ram", ioeventfd_nb = 0, ioeventfds = 0x0}

So it seems this is failing because the memory region "pc.ram" is not an
IOMMU ("is_iommu = false"). I'm not really sure what that means, and I
still don't know how to fix this, but hopefully this information will
help.

If there's any more information I should provide, please let me know.

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  New

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions

[Bug 1920013] Re: Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[Laurent Vivier]

I think cross-arch VFIO has already been discussed in:

https://bugs.launchpad.net/qemu/+bug/1869006

Perhaps you will have some answers.

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  New

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions

[Bug 1920013] Re: Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[cyrozap]

> https://bugs.launchpad.net/qemu/+bug/1869006

Unfortunately, that's not the same issue I'm having, and the error I see
happens regardless of how much or how little RAM I allocate to the VM.

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  New

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions

[Bug 1920013] Re: Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[Thomas Huth]

The QEMU project is currently moving its bug tracking to another system.
For this we need to know which bugs are still valid and which could be
closed already. Thus we are setting the bug state to "Incomplete" now.

If the bug has already been fixed in the latest upstream version of QEMU,
then please close this ticket as "Fix released".

If it is not fixed yet and you think that this bug report here is still
valid, then you have two options:

1) If you already have an account on gitlab.com, please open a new ticket
for this problem in our new tracker here:

    https://gitlab.com/qemu-project/qemu/-/issues

and then close this ticket here on Launchpad (or let it expire auto-
matically after 60 days). Please mention the URL of this bug ticket on
Launchpad in the new ticket on GitLab.

2) If you don't have an account on gitlab.com and don't intend to get
one, but still would like to keep this ticket opened, then please switch
the state back to "New" or "Confirmed" within the next 60 days (other-
wise it will get closed as "Expired"). We will then eventually migrate
the ticket automatically to the new system (but you won't be the reporter
of the bug in the new system and thus you won't get notified on changes
anymore).

Thank you and sorry for the inconvenience.


** Changed in: qemu
       Status: New => Incomplete

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  Incomplete

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions

[Bug 1920013] Re: Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[cyrozap]

I've moved this bug over to GitLab here: https://gitlab.com/qemu-
project/qemu/-/issues/391

** Bug watch added: gitlab.com/qemu-project/qemu/-/issues #391
   https://gitlab.com/qemu-project/qemu/-/issues/391

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  Incomplete

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions

[Bug 1920013] Re: Unable to pass-through PCIe devices from a ppc64le host to an x86_64 guest

[Thomas Huth]

Thanks for moving it over! ... so I'm closing this on Launchpad now.

** Changed in: qemu
       Status: Incomplete => Invalid

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to QEMU.
https://bugs.launchpad.net/bugs/1920013

Title:
  Unable to pass-through PCIe devices from a ppc64le host to an x86_64
  guest

Status in QEMU:
  Invalid

Bug description:
  Attempting to pass through a PCIe device from a ppc64le host to an
  x86_64 guest with QEMU v5.2.0-3031-g571d413b5d (built from git master)
  fails with the following error:

      include/exec/memory.h:43:IOMMU_MEMORY_REGION: Object 0x10438eb00
  is not an instance of type qemu:iommu-memory-region

  To reproduce this issue, simply run the following command on a POWER9
  system:

      qemu-system-x86_64 -machine q35 -device vfio-pci,host=$DBSF

  Where $DBSF is a domain:bus:slot.function PCIe device address.

  This also fails with QEMU 3.1.0 (from Debian Buster), so I assume this
  has never worked. Helpfully, the error message it prints seems to
  indicate where the problem is:

      hw/vfio/spapr.c:147:vfio_spapr_create_window: Object 0x164473510
  is not an instance of type qemu:iommu-memory-region

  My kernel (Linux v5.8.0 plus some small unrelated patches) is built
  with the page size set to 4k, so this issue shouldn't be due to a page
  size mismatch. And as I stated earlier, my host arch is ppc64le, so it
  shouldn't be an endianness issue, either.

  I assume this should be possible (in theory) since I've seen reports
  of others getting PCIe passthrough working with aarch64 guests on
  x86_64 hosts, but of course that (passthrough to weird guest arch on
  x86) is somewhat the opposite of what I'm trying to do (passthrough to
  x86 on weird host arch) so I don't know for sure. If it is possible,
  I'm willing to develop a fix myself, but I'm almost completely
  unfamiliar with QEMU's internals so if anyone has any advice on where
  to start I'd greatly appreciate it.

To manage notifications about this bug go to:
https://bugs.launchpad.net/qemu/+bug/1920013/+subscriptions