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List:       xen-users
Subject:    Re: Cannot pass through PCI/Intel IGD to Debian Bullseye
From:       Chuck Zmudzinski <brchuckz () netscape ! net>
Date:       2021-10-27 15:59:37
Message-ID: d5f8e677-d762-35a3-2d13-008c1d8f9d4b () netscape ! net
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On 10/27/2021 4:36 AM, C Stainer wrote:
> Hi Chuck,
>
> According to Xen Project 4.15 Feature List [0]...
>
> "Increase the maximum number of guests which can share a single IRQ
> from 7 to 16, and make this configurable with irq-max-guests"

Hi C,

Thanks for your reply. I think you misunderstand
my question, maybe I need to simplify it. It is IRQ #16
that was disabled, it is not that I am trying to share an
irq with up to 16 guests. I am doing desktop virtualization
and run at most 4 guests at one time due to memory
limitations on my system. I think this feature is for servers
or workstations with enough memory to run more than
seven guests at a time, but that is not my use case.

Thanks,

Chuck

>
> Compiling latest Xen 4.15 from source may be applicable to your use case? [1]
>
> [0] https://wiki.xenproject.org/wiki/Xen_Project_4.15_Feature_List
> [1] https://wiki.xenproject.org/wiki/Compiling_Xen_From_Source
>
>
> C
>
> On Wed, 27 Oct 2021 at 00:28, Chuck Zmudzinski <brchuckz@netscape.net> wrote:
>> Hello,
>>
>> I am using Xen for Desktop virtualization of Windows and Linux
>> on an older Intel box with a Haswell (4th generation) Intel
>> Integrated Graphics Device (IGD) for graphics which is
>> now fairly old hardware.
>>
>> I use Debian for the dom0 and I also use Xen's Intel IGD
>> passthrough feature for accelerated graphics in an HVM domU.
>>
>> With up-to-date Debian stable version 11.1 (Bullseye) for dom0,
>> PCI/IGD passthrough works well with Windows HVM domUs, but
>> not with modern Linux HVM domUs. I reported this several
>> months ago as a bug to the Debian BTS:
>>
>> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=988333
>>
>> A quick synopsis of that bug report:
>>
>> In the dom0:
>>
>> Debian 11.1 Bullseye version of Xen: 4.14.3-1~deb11u1
>> Debian 11.1 Bullseye version of Qemu: 5.2+dfsg-11+deb11u1
>> Debian 11.1 Bullseye version of Linux kernel: 5.10.70-1
>>
>> Two kinds of guests configured for passthrough (a domain config
>> I use for a Debian 11.1 HVM is added to the end of this message):
>>
>> 1. Windows 10 HVM domU: I can configure it to work well with
>> passthrough of the Intel IGD, the on-board USB card, and the
>> sound card to Windows 10, but only with the rdm_policy set
>> to relaxed hack with my old hardware that, AFAICT, does not
>> isolate passthrough devices optimally.
>>
>> 2. Bullseye Debian 11.1 HVM domU: Passthrough with Intel IGD, USB card
>> and sound card does not work at all
>>
>> The main problem I see in the Debian 11.1 dom0 Journal when starting
>> a Debian 11.1 HVM domU configured for PCI passthrough of the Intel
>> IGD, the USB 3 controller, and the sound card is that IRQ 16 is
>> disabled:
>>
>> ----------------- Start of Journal snippet from dom0 --------------
>> dom0 kernel: irq 16: nobody cared ...
>> ...
>> dom0 kernel: Call Trace:
>> dom0 kernel:  <IRQ>
>> dom0 kernel:  dump_stack+0x6b/0x83
>> dom0 kernel:  __report_bad_irq+0x35/0xa7
>> dom0 kernel:  note_interrupt.cold+0xb/0x61
>> dom0 kernel:  handle_irq_event+0xa8/0xb0
>> ...
>> dom0 kernel: handlers:
>> dom0 kernel: [<00000000ad934388>] usb_hcd_irq [usbcore]
>> dom0 kernel: [<000000003087e3ca>] ath_isr [ath9k]
>> dom0 kernel: Disabling IRQ #16
>> ---------------- End of Journal snippet from dom0 ---------------
>>
>>   From what I have read this is caused by an IRQ being assigned
>> to a device that does not respond to the IRQ. In the dom0, IRQ
>> #16 has been disabled according to the log, but also according
>> to the logs, IRQ #16 is assigned to a PCI device that I do not
>> passthrough. I am thinking perhaps this device assigned to
>> IRQ #16, which is a USB 2 controller, belongs to the same
>> IOMMU group (in VFIO terminology) the USB 3 controller that
>> I do pass through belongs to:
>>
>> dom0 kernel: ehci-pci 0000:00:1a.0: irq 16, io mem 0xf053c000
>>
>> 0000:00:14.0 is the usb 3 controller (xhci) I do passthrough.
>>
>> So I think the problem with the Linux HVM domU is caused by the
>> Linux device drivers in the domU HVM not being as able to deal
>> with the poor isolation of the devices on this old box as well
>> as the Windows drivers do. Am I on the right track? Can this be
>> solved by passing through both this USB 2 controller and the
>> USB 3 controller to the domU?
>>
>> A few more questions:
>>
>> 1. Does anyone report Intel IGD passthrough with a Debian 11
>> dom0 and a Debian 11 domU working on Xen with newer Intel
>> hardware, such as 8th generation or newer?
>>
>> 2. Since IGD passthrough works fine with a Windows HVM, and
>> I also discovered [0] an unmodified Debian 11.1 HVM domU works
>> fine with a slightly modified old version of Debian 8 for
>> the dom0, which uses the old Xen 4.4 hypervisor, the old
>> Linux 3.16 kernel, and the old qemu traditional device model
>> for PCI/IGD passthrough, does anyone know if it is possible
>> to configure or patch the modern Xen 4.14 hypervisor and/or
>> the modern qemu upstream device model to get a modern Debian
>> 11.1 HVM domU to enable PCI/IGD passthrough to work with
>> newer software running in dom0 than what is available from
>> the old Debian 8 release that is now way beyond EOL? I
>> would prefer to be able to get PCI/IGD passthrough to Debian
>> 11.1 to work on a supported dom0 configuration such as a
>> Debian 11.1 dom0 with Xen 4.14 instead of unsupported
>> Debian 8.x dom0 with unsupported Xen 4.4.
>>
>> 3. Is this problem likely to be only limited to certain hardware
>> that does not isolate the devices as well as modern Linux-based
>> software expects?
>>
>> Thanks in advance for any advice you can give me.
>>
>> Regards,
>>
>> Chuck Zmudzinski
>>
>> [0] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=988333#10
>>
>> My domain config file (private data such as mac and ip addresses
>> are redacted):
>>
>> builder = 'hvm'
>> memory = '3072'
>> vcpus = '4'
>> device_model_version = 'qemu-xen'
>> # device_model_version = 'qemu-xen-traditional'
>> # This is a bullseye system (Debian 11.1)
>> disk = ['/dev/systems/linux,,xvda,w','/dev/data/linuxdata,,xvdb,w']
>> name = 'bullseye-hvm'
>> vif = [ 'mac=xx:xx:xx:xx:xx:xx,model=e1000,script=vif-route,ip=A.B.X.Y' ]
>> on_poweroff = 'destroy'
>> on_reboot = 'restart'
>> on_crash = 'restart'
>> boot = 'c'
>> acpi = '1'
>> apic = '1'
>> viridian = '1'
>> xen_platform_pci = '1'
>> serial = 'pty'
>> vga = 'none'
>> sdl = '0'
>> vnc = '0'
>> gfx_passthru = '1'
>> pci = [ '00:1b.0', '00:14.0,rdm_policy=relaxed', '00:02.0' ]
>>


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