PCIe device paththrough via vfio issue

[yurij <lnkgyv@gmail.com>]

Hello everybody!

I have a specific PCIe device (sorry, but I can't tell about what is it 
and what it does) but PCI configuration space consists of 4 BARs (lspci 
output brief):

lspci -s 84:00.00 -vvv

. . .
Region 0: Memory at fa000000 (64-bit, non-prefetchable) [size=16M]
	Region 2: Memory at fb001000 (32-bit, non-prefetchable) [size=4K]
	Region 3: Memory at fb000000 (32-bit, non-prefetchable) [size=4K]
	Region 4: Memory at f9000000 (64-bit, non-prefetchable) [size=16M]
. . .
Kernel driver in use: vfio-pci
. . .

BAR0 merged with BAR1, BAR4 merged with BAR5 so they are 64 bit width.

I put this PCIe device in virtual machine via vfio:

-device vfio-pci,host=84:00.0,id=hostdev0,bus=pci.6,addr=0x0

Virtual machine successfully boot. PCI configuration space in virtual 
environment looks OK (lspci output brief):

lspci -s 06:00.0 -vvv

. . .
Region 0: Memory at f8000000 (64-bit, non-prefetchable) [size=16M]
	Region 2: Memory at fa000000 (32-bit, non-prefetchable) [size=4K]
	Region 3: Memory at fa001000 (32-bit, non-prefetchable) [size=4K]
	Region 4: Memory at f9000000 (64-bit, non-prefetchable) [size=16M]
. . .
Kernel driver in use: custom_driver

BAR0 merged with BAR1 and BAR4 merged with BAR5 and so they are also 64 
bit width.

The main problem in 4K HOLE in REGION 0 in virtual environment. So some 
device features don't work.

I have enabled iommu trace in host system (trace_event=iommu) and 
display all events (for i in $(find 
/sys/kernel/debug/tracing/events/iommu/ -name enable);do echo 1 > $i; 
done). I saw next events during virtual machine booting:

# cat /sys/kernel/debug/tracing/trace
. . .
        CPU 0/KVM-3046  [051] .... 63113.338894: map: IOMMU: 
iova=0x00000000f8000000 paddr=0x00000000fa000000 size=24576
        CPU 0/KVM-3046  [051] .... 63113.339177: map: IOMMU: 
iova=0x00000000f8007000 paddr=0x00000000fa007000 size=16748544
        CPU 0/KVM-3046  [051] .... 63113.339444: map: IOMMU: 
iova=0x00000000fa000000 paddr=0x00000000fb001000 size=4096
        CPU 0/KVM-3046  [051] .... 63113.339697: map: IOMMU: 
iova=0x00000000fa001000 paddr=0x00000000fb000000 size=4096
        CPU 0/KVM-3046  [051] .... 63113.340209: map: IOMMU: 
iova=0x00000000f9000000 paddr=0x00000000f9000000 size=16777216
. . .

I have enabled qemu trace(-trace events=/root/qemu/trace_events). Trace 
file consists of the falling functions:
vfio_region_mmap
vfio_get_dev_region
vfio_pci_size_rom
vfio_pci_read_config
vfio_pci_write_config
vfio_iommu_map_notify
vfio_listener_region_add_iommu
vfio_listener_region_add_ram

Some important brief from qemu trace:
. . .
янв 13 18:17:24 VM qemu-system-x86_64[7131]: vfio_region_mmap Region 
0000:84:00.0 BAR 0 mmaps[0] [0x0 - 0xffffff]
янв 13 18:17:24 VM qemu-system-x86_64[7131]: vfio_region_mmap Region 
0000:84:00.0 BAR 2 mmaps[0] [0x0 - 0xfff]
янв 13 18:17:24 VM qemu-system-x86_64[7131]: vfio_region_mmap Region 
0000:84:00.0 BAR 3 mmaps[0] [0x0 - 0xfff]
янв 13 18:17:24 VM qemu-system-x86_64[7131]: vfio_region_mmap Region 
0000:84:00.0 BAR 4 mmaps[0] [0x0 - 0xffffff]
. . .
янв 13 18:17:37 VM qemu-system-x86_64[7131]: 
vfio_listener_region_add_ram region_add [ram] 0xf8000000 - 0xf8005fff 
[0x7f691e800000]
янв 13 18:17:37 VM qemu-system-x86_64[7131]: 
vfio_listener_region_add_ram region_add [ram] 0xf8007000 - 0xf8ffffff 
[0x7f691e807000]
янв 13 18:17:37 VM qemu-system-x86_64[7131]: 
vfio_listener_region_add_ram region_add [ram] 0xfa000000 - 0xfa000fff 
[0x7f6b5de37000]
янв 13 18:17:37 VM qemu-system-x86_64[7131]: 
vfio_listener_region_add_ram region_add [ram] 0xfa001000 - 0xfa001fff 
[0x7f6b58004000]
янв 13 18:17:37 VM qemu-system-x86_64[7131]: 
vfio_listener_region_add_ram region_add [ram] 0xf9000000 - 0xf9ffffff 
[0x7f691d800000]

I use qemu 4.0.0 which I rebuild for tracing support 
(--enable-trace-backends=syslog).

Please, help me solve this issue. Thank you!

-- 
with best regards
Yurij Goncharuk