Re: [PATCH PROTOTYPE 3/6] vfio: Implement support for sparse RAM memory regions

[David Hildenbrand <david@redhat.com>]

On 20.10.20 22:44, Peter Xu wrote:
> On Tue, Oct 20, 2020 at 10:01:12PM +0200, David Hildenbrand wrote:
>> Thanks ... but I have an AMD system. Will try to find out how to get
>> that running with AMD :)
> 
> May still start with trying intel-iommu first. :) I think it should work for
> amd hosts too.
> 
> Just another FYI - Wei is working on amd-iommu for vfio [1], but it's still
> during review.
> 
> [1] https://lore.kernel.org/qemu-devel/20201002145907.1294353-1-wei.huang2@amd.com/
> 

I'm trying to get an iommu setup running (without virtio-mem!),
but it's a big mess.

Essential parts of my QEMU cmdline are:

sudo build/qemu-system-x86_64 \
    -accel kvm,kernel-irqchip=split \
    ...
     device pcie-pci-bridge,addr=1e.0,id=pci.1 \
    -device vfio-pci,host=0c:00.0,x-vga=on,bus=pci.1,addr=1.0,multifunction=on \
    -device vfio-pci,host=0c:00.1,bus=pci.1,addr=1.1 \
    -device intel-iommu,caching-mode=on,intremap=on \

I am running upstream QEMU + Linux -next kernel inside the
guest on an AMD Ryzen 9 3900X 12-Core Processor.
I am using SeaBios.

I tried faking an Intel CPU without luck.
("-cpu Skylake-Client,kvm=off,vendor=GenuineIntel")

As soon as I enable "intel_iommu=on" in my guest kernel, graphics
stop working (random mess on graphics output) and I get
  vfio-pci 0000:0c:00.0: AMD-Vi: Event logged [IO_PAGE_FAULT domain=0x0023 address=0xff924000 flags=0x0000]
in the hypervisor, along with other nice messages.

I can spot no vfio DMA mappings coming from an iommu, just as if the
guest wouldn't even try to setup the iommu.

I tried with
1. AMD Radeon RX Vega 56
2. Nvidia GT220
resulting in similar issues.

I also tried with "-device amd-iommu" with other issues
(guest won't even boot up). Are my graphics card missing some support or
is there a fundamental flaw in my setup?

Any clues appreciated.


-- 
Thanks,

David / dhildenb