TL;DR point 2. is wrong, pcie-port, vfio-pci or pci-stub are allowed, see
"IOMMU groups inside and out" blog post.
On Apr 12, 2016 11:30 PM, "Bronek Kozicki" <b...@spamcop.net> wrote:
> On 12/04/2016 20:36, Nicolas Roy-Renaud wrote:
>
>> I've already rewritten the first two sections ("Prerequisites" and
>> "Setting up IOMMU"), and the rest of the article should essentially
>> follow the same basic structure and style. Replies here or on the wiki's
>> discussion page would be much appreciated.
>>
>
> Hope Alex can clear any misconception I am about to present below
>
>
> 1. I am using option iommu=pt, under impression this is expected to
> improve performance (my CPU is Xeon IvyBridge)
>
> 2. does PCI bridge have to be in a separate IOMMU group than
> passed-through device?
>
> 3. would be nice to provide hints for headless host. FWIW, I use
> combination of
> 3.1. kernel options:
> console=ttyS0,115200N8R nomodest video=vesa:off video=efifb:off vga=normal
> 3.2.following line in /etc/modprobe.d/vfio.conf:
> options vfio-pci disable_vga=1
> 3.3. large list of blacklisted modules (all framebuffers and nvidia and
> AMD drivers) in /etc/modprobe.d/blacklist.conf:
> # This host is headless, prevent any modules from attaching to video
> hardware
> # NVIDIA
> blacklist nouveau
> blacklist nvidia
> # AMD
> blacklist radeon
> blacklist amdgpu
> blacklist amdkfd
> blacklist fglrx
> # HDMI sound on a GPU
> blacklist snd_hda_intel
> # Framebuffers (ALL of them)
> blacklist vesafb
> blacklist aty128fb
> blacklist atyfb
> blacklist radeonfb
> blacklist cirrusfb
> blacklist cyber2000fb
> blacklist cyblafb
> blacklist gx1fb
> blacklist hgafb
> blacklist i810fb
> blacklist intelfb
> blacklist kyrofb
> blacklist lxfb
> blacklist matroxfb_base
> blacklist neofb
> blacklist nvidiafb
> blacklist pm2fb
> blacklist rivafb
> blacklist s1d13xxxfb
> blacklist savagefb
> blacklist sisfb
> blacklist sstfb
> blacklist tdfxfb
> blacklist tridentfb
> blacklist vfb
> blacklist viafb
> blacklist vt8623fb
> blacklist udlfb
>
> 4. ignore_msrs=1 also helps running Linux guests
>
> 5. do not use qemu:arg for binding host device to guest, here is example
> how to do it properly:
> <hostdev mode='subsystem' type='pci' managed='yes'>
> <driver name='vfio'/>
> <source>
> <address domain='0x0000' bus='0x82' slot='0x00' function='0x0'/>
> </source>
> <address type='pci' domain='0x0000' bus='0x00' slot='0x08'
> function='0x0'/>
> </hostdev>
> 5.1. for nVidia Quadro, add just below </source ...>
> <rom bar='off'/>
>
> 6. if guest is started from BIOS rather than UEFI, keep the above <hostdev
> ...> but replace emulator with a script, e.g.
> # virsh dumpxml gdynia-vfio1 | grep emulator
> <emulator>/usr/bin/qemu-system-x86_64.xvga.sh</emulator>
> # cat /usr/bin/qemu-system-x86_64.xvga.sh
> #!/bin/sh
> exec nice --adjustment=-5 /usr/bin/qemu-system-x86_64 `echo "$@" | \
> sed 's/-device vfio-pci,host=82:00.0/-device
> vfio-pci,host=82:00.0,x-vga=on/g' | \
> sed 's/-device vfio-pci,host=03:00.0/-device
> vfio-pci,host=03:00.0,x-vga=on/g'`
>
>
> 7. performance optimizations
> 7.1. use huge pages
> 7.2. use isolcpus
> 7.3. use vCPU pinnig
> 7.4. use virtio-scsi with multiple queues (depending on number of
> available CPUs, after removing these dedicated to guest)
> 7.5. use multiple queues for virtio-net
> 7.6. for Linux guests, use P9 for mounting host filesystems in guest
>
>
>
>
> B.
>
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