Re: [Qemu-devel] VFIO VGA test branches

[Alex Williamson]

On Mon, 2013-05-13 at 22:55 +0200, Knut Omang wrote:
> Hi all,
> 
> Perfect timing from my perspective, thanks Alex!
> 
> I spent the better part of the weekend testing your branches on a new system 
> I just put together for this purpose, results below..
> 
> On Fri, 2013-05-03 at 16:56 -0600, Alex Williamson wrote:
> ...
> > git://github.com/awilliam/linux-vfio.git vfio-vga-reset
> > git://github.com/awilliam/qemu-vfio.git vfio-vga-reset
> 
> System setup: 
> 
> - Fedora 18 on
> - Gigabyte Z77X-UD5H motherboard
> - Intel Core i7 3770 (Ivy bridge w/integrated graphics)
> - 2 discrete graphics cards:
> 
> lspci | egrep 'VGA|Audio'
> 00:02.0 VGA compatible controller: Intel Corporation Xeon E3-1200 v2/3rd Gen 
> Core processor Graphics Controller (rev 09)
> 00:1b.0 Audio device: Intel Corporation 7 Series/C210 Series Chipset Family 
> High Definition Audio Controller (rev 04)
> 01:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI 
> Caicos [Radeon HD 6450]
> 01:00.1 Audio device: Advanced Micro Devices [AMD] nee ATI Caicos HDMI Audio 
> [Radeon HD 6400 Series]
> 02:00.0 VGA compatible controller: Advanced Micro Devices [AMD] nee ATI Cape 
> Verde PRO [Radeon HD 7700 Series]
> 02:00.1 Audio device: Advanced Micro Devices [AMD] nee ATI Cape 
> Verde/Pitcairn HDMI Audio [Radeon HD 7700/7800 Series]
> 
> Short summary:
> 
> - Once I got past a few time consuming obstacles explained below
>    - the graphics part of the graphics/hdmi audio passthrough seems to work 
> perfect
>      on both discrete graphics cards 
>      (though so far only one at at time and with some minor issues, see below)
>    - no success with the hdmi audio yet (ideas for further investigation 
> appreciated!)

I've had hdmi audio working with an HD7850, but only in Windows (7) and
it was using legacy interrupts for some reason instead of MSI.  I wonder
if Liux guests might work with snd_hda_intel.enable_msi=0.  I'm not sure
what's wrong with MSI, but it seems to be new with the PCI bus reset
support.

> - Contrary to address@hidden I had no success with using pci-assign for VGA
>   with a standard fedora 18 kernel and fairly recent qemu, nor with your 
> branches, 
> 
> Details:
> 
> - I started off with the required kernel parameter 'intel_iommu=on' + 
> necessary parameters for disabling radeon
>    (radeon.modeset=0 rd.driver.blacklist=radeon) using the integrated 
> graphics as primary display
>    - this caused the system to freeze (with color artifacts on the console)
> 
> - In my naivity and because of the "i" in ifgx I tried both with 
>   'intel_iommu=ifgx_off' and then 'intel_iommu=on,igfx_off' 
>   and a full set of combinations of vfio, cards, kernels and pci-assign 
> before I suspected 
>   that iommu support was turned off for **all** graphics cards with igfx_off

I'm not sure why this is, looks like the code only tries to turn it off
when only graphics is under the remapping device.  We'd probably need to
see the DMAR to know more (/sys/firmware/acpi/tables/DMAR).

> - The solution was to have integrated graphics turned off in the BIOS, and 
> 'intel_iommu=on':
> 
> - iommu groups:
> 
> ls -l /sys/bus/pci/devices/0000:01:00.0/iommu_group/devices
> total 0
> lrwxrwxrwx 1 root root 0 May 11 08:55 0000:00:01.0 -> 
> ../../../../devices/pci0000:00/0000:00:01.0
> lrwxrwxrwx 1 root root 0 May 11 08:55 0000:00:01.1 -> 
> ../../../../devices/pci0000:00/0000:00:01.1
> lrwxrwxrwx 1 root root 0 May 11 08:55 0000:01:00.0 -> 
> ../../../../devices/pci0000:00/0000:00:01.0/0000:01:00.0
> lrwxrwxrwx 1 root root 0 May 11 08:55 0000:01:00.1 -> 
> ../../../../devices/pci0000:00/0000:00:01.0/0000:01:00.1
> lrwxrwxrwx 1 root root 0 May 11 08:55 0000:02:00.0 -> 
> ../../../../devices/pci0000:00/0000:00:01.1/0000:02:00.0
> lrwxrwxrwx 1 root root 0 May 11 08:55 0000:02:00.1 -> 
> ../../../../devices/pci0000:00/0000:00:01.1/0000:02:00.1
> 
> - eg. both the VGA/HDMI Audio pairs + the two root ports they are plugged 
> into are in the same group:

Ick.  Intel has been pretty good about advertising ACS support on their
root ports.  I wonder if this is an oversight or if they are actually
not isolated from each other.

> # lspci -n
> ...
> 01:00.0 0300: 1002:683f
> 01:00.1 0403: 1002:aab0
> 02:00.0 0300: 1002:6779
> 02:00.1 0403: 1002:aa98
> ...
> 
> modprobe vfio_pci
> echo 0000:01:00.1 > /sys/bus/pci/devices/0000\:01\:00.1/driver/unbind
> echo 0000:02:00.1 > /sys/bus/pci/devices/0000\:02\:00.1/driver/unbind
> echo 1002 683f > /sys/bus/pci/drivers/vfio-pci/new_id
> echo 1002 aab0 > /sys/bus/pci/drivers/vfio-pci/new_id
> echo 1002 6779 > /sys/bus/pci/drivers/vfio-pci/new_id
> echo 1002 aa98 > /sys/bus/pci/drivers/vfio-pci/new_id
> 
> # lsusb 
> ...
> Bus 001 Device 008: ID 046d:c315 Logitech, Inc. Classic New Touch Keyboard
> Bus 001 Device 004: ID 046d:c05b Logitech, Inc. M-U0004 810-001317 [B110 
> Optical USB Mouse]
> ...
> 
> - I also applied your suggested patch to the quirk function in VFIO (see 
> below)
> 
> - Here is a (trimmed for readability) command line I successfully used to 
> boot from the Windows 7 install DVD, 
>   notice the cd and disk device descriptions and the bus parameter - I 
> struggled a while with that 
>   until I came across a comment by Gerd Hoffmann here: 
> https://bugzilla.redhat.com/show_bug.cgi?id=922670 (Thanks, Gerd!)
> 
> 
> qemu-kvm -M q35 \
>   -nodefconfig -readconfig $SRC/qemu/docs/q35-chipset.cfg \
>   -device 
> vfio-pci,host=2:00.0,x-vga=on,multifunction=on,bus=ich9-pcie-port-1,addr=0.0 \
>   -device vfio-pci,host=2:00.1,bus=ich9-pcie-port-1,addr=0.1 \
>   -L $SRC/seabios/out/ -L $SRC/qemu/pc-bios \
>   -vga none -nographic -cpu host -rtc base=localtime -k no -m 8192 -smp 2 \
>   -drive file=/dev/sr0,index=2,media=cdrom,id=cd \
>   -drive file=ivm03.img,index=0,media=disk,id=ivm03 \
>   -device ide-drive,drive=ivm03,bus=ide.0 \
>   -device ide-cd,drive=cd,bus=ide.1 \
>   -net nic,vlan=0,model=virtio -net tap,vlan=0 \
>   -enable-kvm \
>   -device usb-host,hostbus=1,hostaddr=8 \
>   -device usb-host,hostbus=1,hostaddr=4
> 
> - Both the graphics card seemshould really support ACS on s to have a rom but 
> only the HD6450 let itself to "scraping". 

Did you try scraping the HD6450 while the HD7700 was the boot VGA and
vica versa?  The boot VGA ROM is handled in a special way and what you
really get is the shadow copy, which isn't what we want.

> Anyway, supplying it to vfio did not seem to make any difference.
> 
> find /sys -name rom
> /sys/devices/pci0000:00/0000:00:01.0/0000:01:00.0/rom
> /sys/devices/pci0000:00/0000:00:01.1/0000:02:00.0/rom
> ...
> 
> Some observations and remaining unresolved issues:
> 
> - VFIO patch:
>   Initially (while still running with igfx_off) I observed exactly the same 
> behaviour as address@hidden
>   reported a while ago: With vfio_pci debug enabled, vfio_pci ended up 
> spinning with repeated calls to
>   vfio_ati_3c3_quirk_read and repeated logs: 
>     vfio: vfio_vga_read(0x3c3, 1) = 0x0
>   I patched up accordingly with 
> 
> 
> diff --git a/hw/misc/vfio.c b/hw/misc/vfio.c
> index da0e5f9..a361d06 100644
> --- a/hw/misc/vfio.c
> +++ b/hw/misc/vfio.c
> @@ -1291,7 +1291,7 @@ static uint64_t vfio_ati_3c3_quirk_read(void *opaque,
>      uint64_t data = vfio_vga_read(&vdev->vga.region[QEMU_PCI_VGA_IO_HI],
>                                    addr + quirk->data.base_offset, size);
>  
> -    if (data == quirk->data.address_match) {
> +    if (1 || data == quirk->data.address_match) {
>          data = vfio_pci_read_config(&vdev->pdev, quirk->data.address_val, 
> size);
>          DPRINTF("%s(0x3c3, 1) = 0x%"PRIx64"\n", __func__, data);
>      }
> 
> 
>   This of course did not help much until I actually got the iommu 
>   enabled for the radeons (similar "repeated patters" as deniv reported)
>   but what I have observed after I got it working is that if 
>   I disable the patch above, things are not that well: the Fedora VM 
>   comes up with VGA and the Fedora boot screen, then goes blank when 
>   switching to X.

Hmm, I think we'd probably have better luck making that unconditional
until we have reason to do otherwise.

> - The fact that the iommu group now extends across all my available graphics 
>   devices now makes it difficult to  get the radeon (or catalyst) driver use 
> to 
>   the other card since the vfio_pci driver needs to hold it.
>   Not a complete showstopper since the vesa driver comes up with 1024x768..
>   Might it be a good idea to have an override option (exception list or 
> similar?) 
>   to allow the vfio_pci to be less restrictive about owning the whole group 
>    - allow functionality over security in such case? This of course is 
> further complicated
>   by the need for graphics drivers to be disabled/enabled already at the 
> kernel prompt..

We have a quirk in the kernel that enables us to witelist devices, but
yes, there is no flexibility in this w/o modifying the code and
rebuilding.  (see drivers/pci/quirks.c:pci_dev_acs_enabled and follow
the example above w/ pci_dev_dma_source - function can just return 1)

> - There seems to be a bug in the (version F8) UEFI BIOS on the motherboard, 
>   The BIOS offers (undocumented) a full range of selections of which PCIe 
>   (or PCIe 1x) graphics card to use as primary, but any other selection 
>   than the first PCIe 16x slot has no effect and the motherboard reverts 
>   to the first slot, so to be able to test both cards, I had to put the card 
> under test
>   into the second (8x) PCIe slot. I am waiting for feedback from Gigabyte on 
> possible 
>   fixes for this in newer BIOSes.
> 
> - The ultimate goal is to try to consolidate some older Windows desktops as 
> "seats" 
>   on the new system, using the discrete graphics with HDMI/Displayport audio. 
>   With the HD7700 moved to the second PCIe slot I tested both Windows and 
>   Linux guests to try to get some sound through the HDMI audio device. 
>   Windows complains that no usable device is available. On Linux (Fedora 18, 
> KDE desktop), 
>   the system settings -> multimedia dialogue never opens up which seems to 
> indicate that 
>   PulseAudio has problems communicating with the passed through device (?), 
>   any hints/pointers here appreciated. From the vfio log it seems at least
>   config space is accessed ok.
> 
> - There also seems to be issues with radeon and intel_iommu=on - if I try 
>   to enable modesetting and normal X support for the radeon cards, X fails to 
> start.
> 
> - It would be nice if the integrated graphics could be used as the host 
> primary display - 
>   I would be happy if someone has any hints as to if/how the ifgx_off option 
>   could be extended/modified to only affect iommu operation on selected 
> device(s),
>   if at all possible..

Let's see what we can discover from your DMAR.  Also send along sudo
lspci -vvv.  Thanks,

Alex