Re: PCIe device paththrough via vfio issue

[yurij]

On 1/13/20 7:28 PM, Alex Williamson wrote:
> On Mon, 13 Jan 2020 18:49:21 +0300
> yurij <address@hidden> wrote:
>
> > 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!
>
> Something has probably created a QEMU MemoryRegion overlapping the BAR,
> we do this for quirks where we want to intercept a range of MMIO for
> emulation, but the offset 0x6000 on BAR0 doesn't sound familiar to me.
> Run the VM with a monitor and see if 'info mtree' provides any info on
> the handling of that overlap.  Thanks,
>
> Alex

I have seen lspci more closely and find offset 0x6000 on BAR0:
. . .
        Capabilities: [90] MSI-X: Enable- Count=32 Masked-
                Vector table: BAR=0 offset=00006000
                PBA: BAR=0 offset=00007000
. . .

I have enabled next trace functions:
vfio_msix_vector_do_use
vfio_msix_vector_release
vfio_msix_enable
vfio_msix_pba_disable
vfio_msix_pba_enable
vfio_msix_disable
vfio_msix_fixup
vfio_msix_relo
vfio_msix_early_setup


Start virtual machine and see:
. . .
янв 14 16:18:49 VM qemu-system-x86_64[3645]: vfio_msix_early_setup 
0000:84:00.0 PCI MSI-X CAP @0x90, BAR 0, offset 0x6000, entries 32
. . .

So qemu split BAR0 due to MSI-X capailities. Is it true? If it seems to 
be true I need to patch qemu pci-quirks.c to add vfio_quirk_ function 
that will be workaround about my device? Can I disable allocation space 
for MSI-X capability (my device doesn't use MSI-X)?

P.S.
> Run the VM with a monitor and see if 'info mtree' provides any info on
> the handling of that overlap.  Thanks,
Can you explain to me, how can I use 'mtree' (debugging scenario)? I 
have never use 'mtree' and don't imagine about usage scenario.

Thank you!

--
with best regards
Yurij Goncharuk