[Bug 1869006] Re: PCIe cards passthrough to TCG guest works on 2GB of guest memory but fails on 4GB (vfio_dma_map invalid arg)

[costinel]

I am experiencing the same behaviour for x86_64 guest on x86_64 host to
which I'm attempting to efi boot (not hotplug) with a pcie gpu
passthrough

This discussion (https://www.spinics.net/lists/iommu/msg40613.html)
suggests a change in drivers/iommu/intel-iommu.c but it appears that in
the kernel I tried, the change it is already implemented (linux-
image-5.4.0-39-generic)

hardware is a hp microserver gen8 with conrep physical slot excluded in
bios (https://www.jimmdenton.com/proliant-intel-dpdk/) and the kernel is
rebuild with rmrr patch (https://forum.proxmox.com/threads/compile-
proxmox-ve-with-patched-intel-iommu-driver-to-remove-rmrr-check.36374/)

also an user complains that on the same hardware it used to work with
kernel 5.3 + rmrr patch (https://forum.level1techs.com/t/looking-for-
vfio-wizards-to-troubleshoot-error-vfio-dma-map-22/153539) but it
stopped working on the 5.4 kernel.

is this the same issue I'm observing? my qemu complains with the similar
message:

 -device vfio-pci,host=07:00.0,id=hostdev0,bus=pci.4,addr=0x0:
vfio_dma_map(0x556eb57939f0, 0xc0000, 0x3ff40000, 0x7f6fc7ec0000) = -22
(Invalid argument)

/sys/kernel/iommu_groups/1/reserved_regions shows:

0x00000000000e8000  0x00000000000e8fff direct
0x00000000000f4000 0x00000000000f4fff direct
0x00000000d5f7e000 0x00000000d5f94fff direct
0x00000000fee00000 0x00000000feefffff msi

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https://bugs.launchpad.net/bugs/1869006

Title:
  PCIe cards passthrough to TCG guest works on 2GB of guest memory but
  fails on 4GB (vfio_dma_map invalid arg)

Status in QEMU:
  New

Bug description:
  During one meeting coworker asked "did someone tried to passthrough
  PCIe card to other arch guest?" and I decided to check it.

  Plugged SATA and USB3 controllers into spare slots on mainboard and
  started playing. On 1GB VM instance it worked (both cold- and hot-
  plugged). On 4GB one it did not:

  Błąd podczas uruchamiania domeny: internal error: process exited while 
connecting to monitor: 2020-03-25T13:43:39.107524Z qemu-system-aarch64: -device 
vfio-pci,host=0000:29:00.0,id=hostdev0,bus=pci.3,addr=0x0: VFIO_MAP_DMA: -22
  2020-03-25T13:43:39.107560Z qemu-system-aarch64: -device 
vfio-pci,host=0000:29:00.0,id=hostdev0,bus=pci.3,addr=0x0: vfio 0000:29:00.0: 
failed to setup container for group 28: memory listener initialization failed: 
Region mach-virt.ram: vfio_dma_map(0x563169753c80, 0x40000000, 0x100000000, 
0x7fb2a3e00000) = -22 (Invalid argument)

  Traceback (most recent call last):
    File "/usr/share/virt-manager/virtManager/asyncjob.py", line 75, in 
cb_wrapper
      callback(asyncjob, *args, **kwargs)
    File "/usr/share/virt-manager/virtManager/asyncjob.py", line 111, in tmpcb
      callback(*args, **kwargs)
    File "/usr/share/virt-manager/virtManager/object/libvirtobject.py", line 
66, in newfn
      ret = fn(self, *args, **kwargs)
    File "/usr/share/virt-manager/virtManager/object/domain.py", line 1279, in 
startup
      self._backend.create()
    File "/usr/lib64/python3.8/site-packages/libvirt.py", line 1234, in create
      if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
  libvirt.libvirtError: internal error: process exited while connecting to 
monitor: 2020-03-25T13:43:39.107524Z qemu-system-aarch64: -device 
vfio-pci,host=0000:29:00.0,id=hostdev0,bus=pci.3,addr=0x0: VFIO_MAP_DMA: -22
  2020-03-25T13:43:39.107560Z qemu-system-aarch64: -device 
vfio-pci,host=0000:29:00.0,id=hostdev0,bus=pci.3,addr=0x0: vfio 0000:29:00.0: 
failed to setup container for group 28: memory listener initialization failed: 
Region mach-virt.ram: vfio_dma_map(0x563169753c80, 0x40000000, 0x100000000, 
0x7fb2a3e00000) = -22 (Invalid argument)

  
  I played with memory and 3054 MB is maximum value possible to boot VM with 
coldplugged host PCIe cards.

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