12:07 p.m.
Greetings Michal,
Sent: Monday, August 26, 2024 at 12:42 PM
From: "Michal Prívozník" <mprivozn(a)redhat.com>
To: "daggs" <daggs(a)gmx.com>, users(a)lists.libvirt.org
Subject: Re: splitting a bt wifi combo between two vms
On 8/26/24 10:37, daggs via Users wrote:
> Greetings,
>
> I have the following combo device:
> dagg@NCC-5001D ~ $ lsusb -d8087:0029
> Bus 001 Device 002: ID 8087:0029 Intel Corp. AX200 Bluetooth
> dagg@NCC-5001D ~ $ lspci -vv -s 03:00.0
> 03:00.0 Network controller: Intel Corporation Wi-Fi 6 AX200 (rev 1a)
> Subsystem: Intel Corporation Wi-Fi 6 AX200NGW
> Control: I/O- Mem+ BusMaster- SpecCycle- MemWINV- VGASnoop- ParErr-
Stepping- SERR- FastB2B- DisINTx-
> Status: Cap+ 66MHz- UDF- FastB2B- ParErr- DEVSEL=fast >TAbort-
<TAbort- <MAbort- >SERR- <PERR- INTx-
> Interrupt: pin A routed to IRQ 34
> IOMMU group: 13
> Region 0: Memory at fc600000 (64-bit, non-prefetchable) [size=16K]
> Capabilities: <access denied>
> Kernel modules: iwlwifi
>
> I want to pass each of them to a different vm.
> should I expect problems?
If you assign a PCI device to a VM then the host has to release it.
You're not showing the full PCI device config (I assume bluetooth is
another PCI function), but I'd assume it's all or nothing. I don't think
I've seen a PCI device that allows detaching a single PCI function
(apart from SRIO-V, which are specifically designed to do this). IOW, if
you assign the 03:00.0 PCI device to a VM then the other function
(bluetooth) has to be detached too at which point it can not be assigned
to another VM.
This can be verified via virsh:
virsh nodedev-dumpxml pci_0000_03_00_0
in the printed XML you'll find <iommuGroup/> element, e.g.:
<iommuGroup number='14'>
<address domain='0x0000' bus='0x03' slot='0x00'
function='0x0'/>
</iommuGroup>
If there's just one <address/> child element, then the device is in its
own iommu group and can be detached alone. If there are multiple child
elements, e.g.:
<iommuGroup number='16'>
<address domain='0x0000' bus='0x07' slot='0x01'
function='0x0'/>
<address domain='0x0000' bus='0x07' slot='0x04'
function='0x0'/>
<address domain='0x0000' bus='0x08' slot='0x00'
function='0x0'/>
<address domain='0x0000' bus='0x07' slot='0x00'
function='0x0'/>
<address domain='0x0000' bus='0x06' slot='0x00'
function='0x0'/>
<address domain='0x0000' bus='0x04' slot='0x01'
function='0x0'/>
</iommuGroup>
then all devices within the iommu group have to be detached from the
host before giving any device to a VM.
Michal
that is the thing, from what I can see, this combo device has a pci device which is the
wifi, see:
$ tail /sys/bus/pci/devices/0000\:03\:00.0/{device,vendor}
==> /sys/bus/pci/devices/0000:03:00.0/device <==
0x2723
==> /sys/bus/pci/devices/0000:03:00.0/vendor <==
0x8086
dagg@NCC-5001D ~ $ ll /sys/bus/pci/devices/0000\:03\:00.0/iommu_group
lrwxrwxrwx 1 root root 0 Aug 26 09:44 /sys/bus/pci/devices/0000:03:00.0/iommu_group ->
../../../../../../kernel/iommu_groups/13
while the bt is a usb device, see:
$ tail /sys/bus/usb/devices/1-5/id*
==> /sys/bus/usb/devices/1-5/idProduct <==
0029
==> /sys/bus/usb/devices/1-5/idVendor <==
8087
both of them are AX200
Dagg