QEMU/KVM and GPU Passthrough Troubleshooting

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Guest GPU Au­dio Crack­ling and IRQ xx: No­body Cared Fix

Win­dows

The so­lu­tion of the is­sue Guest GPU HD­MI Au­dio Crack­ling, Bro­ken or Los­ing is well ex­plained by Jonp at UN­RAID Fo­rums. In short we must try to en­able the MSI – Mes­sage Sig­naled In­ter­rupts op­tion if the de­vice sup­port it. Here is a de­tailed step-by-step in­struc­tion how to do that.

I was men­tioned the ker­nel com­mand irqpool as so­lu­tion for this is­sue, but in my opin­ion and ac­cord­ing to some oth­er posts, pro­vid­ed in the ref­er­ences sec­tion, this set­ting is an ac­tu­al so­lu­tion for the prob­lem irq 44: no­body cared (try boot­ing with the "irqpool" op­tion); han­dlers: vfio_​​​intx_​​​handler; Dis­abling IRQ #44, that ap­pears at my sys­tem when boot­ing a VM with GPU passthrough with a dis­play at­tached to it, which was caus­ing host sys­tem re­boot.

Lin­ux

Lin­ux guests usu­al­ly en­able MSI by them­selves. To force use of MSI for GPU au­dio de­vices, use the fol­low­ing com­mand and re­boot.

sudo lspci -nnv -s 02:00
  • Note the lines Ker­nel dri­ver in use: vfio-pci
#Out­put
02:00.0 VGA compatible controller [0300]: NVIDIA Corporation GF119 [NVS 315] [10de:107c] (rev a1) (prog-if 00 [VGA controller])
        Subsystem: NVIDIA Corporation GF119 [NVS 315] [10de:102f]
        Physical Slot: 1
        Flags: bus master, fast devsel, latency 0, IRQ 255, NUMA node 0
        Memory at fa000000 (32-bit, non-prefetchable) [size=16M]
        Memory at 23ff0000000 (64-bit, prefetchable) [size=128M]
        Memory at 23ff8000000 (64-bit, prefetchable) [size=32M]
        I/O ports at d000 [size=128]
        Expansion ROM at fb000000 [disabled] [size=512K]
        Capabilities: [60] Power Management version 3
        Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
        Capabilities: [78] Express Endpoint, MSI 00
        Capabilities: [b4] Vendor Specific Information: Len=14 <?>
        Capabilities: [100] Virtual Channel
        Capabilities: [128] Power Budgeting <?>
        Capabilities: [600] Vendor Specific Information: ID=0001 Rev=1 Len=024 <?>
        Kernel driver in use: vfio-pci
        Kernel modules: nvidiafb, nouveau, nvidia_drm, nvidia

02:00.1 Audio device [0403]: NVIDIA Corporation GF119 HDMI Audio Controller [10de:0e08] (rev a1)
        Subsystem: NVIDIA Corporation GF119 HDMI Audio Controller [10de:102f]
        Physical Slot: 1
        Flags: fast devsel, IRQ 255, NUMA node 0
        Memory at fb080000 (32-bit, non-prefetchable) [disabled] [size=16K]
        Capabilities: [60] Power Management version 3
        Capabilities: [68] MSI: Enable- Count=1/1 Maskable- 64bit+
        Capabilities: [78] Express Endpoint, MSI 00
        Kernel driver in use: vfio-pci
        Kernel modules: snd_hda_intel

Ref­er­ences

Hide the Warn­ings KVM: vcpu0 ig­nored rdm­sr

sudo nano /etc/modprobe.d/kvm.conf
options kvm report_ignored_msrs=0 # Or: GRUB_CMDLINE_LINUX_DEFAULT="... kvm.report_ignored_msrs=0 ..."
sudo update-initramfs -u -k all
  • Note, ac­cord­ing to my ex­pe­ri­ence, this op­tion may cause crash­es of the host sys­tem!?

Ref­er­ences

KVM Mod­e­in­fo

modinfo kvm
filename:       /lib/modules/5.4.0-77-generic/kernel/arch/x86/kvm/kvm.ko
license:        GPL
author:         Qumranet
srcversion:     20C68083F39E14AB616D0B8
depends:
retpoline:      Y
intree:         Y
name:           kvm
vermagic:       5.4.0-77-generic SMP mod_unload modversions
sig_id:         PKCS#7
signer:         Build time autogenerated kernel key
sig_key:        67:66:2F:F8:26:8F:56:E9:37:7F:B7:AD:33:FA:97:31:CA:7F:FF:50
sig_hashalgo:   sha512
signature:      6C:0B:65:F9:46:AC:D8:B7:94:E8:B9:9D:A0:4B:97:E6:63:52:5A:FF:
                ...
parm:           nx_huge_pages:bool
parm:           nx_huge_pages_recovery_ratio:uint
parm:           ignore_msrs:bool
parm:           report_ignored_msrs:bool
parm:           min_timer_period_us:uint
parm:           kvmclock_periodic_sync:bool
parm:           tsc_tolerance_ppm:uint
parm:           lapic_timer_advance_ns:int
parm:           vector_hashing:bool
parm:           enable_vmware_backdoor:bool
parm:           force_emulation_prefix:bool
parm:           pi_inject_timer:bint
parm:           halt_poll_ns:uint
parm:           halt_poll_ns_grow:uint
parm:           halt_poll_ns_grow_start:uint
parm:           halt_poll_ns_shrink:uint