Re: PCIe device paththrough via vfio issue

[yurij]

On 1/14/20 5:04 PM, Alex Williamson wrote:
> On Tue, 14 Jan 2020 17:14:33 +1100
> Alexey Kardashevskiy <address@hidden> wrote:
>
> > On 14/01/2020 03:28, 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,
> >
> >
> > Could not it be an MSIX region? 'info mtree -f' should tell exactly what
> > is going on.
>
> Oh, good call, that's probably it.  The PCI spec specifically
> recommends against placing non-MSIX related registers within the same
> 4K page as the vector table to avoid such things:
>
>   If a Base Address register that maps address space for the MSI-X Table
>   or MSI-X PBA also maps other usable address space that is not
>   associated with MSI-X structures, locations (e.g., for CSRs) used in
>   the other address space must not share any naturally aligned 4-KB
>   address range with one where either MSI-X structure resides. This
>   allows system software where applicable to use different processor
>   attributes for MSI-X structures and the other address space.
>
> We have the following QEMU vfio-pci device option to relocate the BAR
> elsewhere for hardware that violates that recommendation or for where
> the PCI spec recommended alignment isn't sufficient:
>
>   x-msix-relocation=<OffAutoPCIBAR> - off/auto/bar0/bar1/bar2/bar3/bar4/bar5
>
> In this case I'd probably recommend bar2 or bar3 as those BARs would
> only be extended to 8K versus bar0/4 would be extended to 32M.  Thanks,
>
> Alex

>   x-msix-relocation=<OffAutoPCIBAR> - 
off/auto/bar0/bar1/bar2/bar3/bar4/bar5

I have used successfully 'x-msix-relocation' option:
-device 
vfio-pci,host=84:00.0,id=hostdev0,bus=pci.6,addr=0x0,x-msix-relocation=bar2

Now,  IOMMU trace looks like:
. . .
       CPU 0/KVM-4237  [055] ....  4750.918416: map: IOMMU: 
iova=0x00000000f8000000 paddr=0x00000000fa000000 size=16777216
       CPU 0/KVM-4237  [055] ....  4750.918740: map: IOMMU: 
iova=0x00000000fa000000 paddr=0x00000000fb001000 size=4096
       CPU 0/KVM-4237  [055] ....  4750.919069: map: IOMMU: 
iova=0x00000000fa002000 paddr=0x00000000fb000000 size=4096
       CPU 0/KVM-4237  [055] ....  4750.919698: map: IOMMU: 
iova=0x00000000f9000000 paddr=0x00000000f9000000 size=16777216
. . .

All seems to be OK.

Thank you very much!

--
with best regards
Yurij Goncharuk