Commit 11bc4a13 (Nov 13, 2019, merged after v4.2.0-rc5) moved the kernel-irqchip parameter to -accel, but I think the default was inadvertently changed to off. The documentation was changed to say the default is on, but the code change seems to have done the opposite.
I found this when I tested my Windows Server 2016 VMs with the last qemu from git. Windows boots and runs very slowly unless I add either <ioapic driver='kvm'/> (kernel_irqchip=on) or <timer name="hypervclock" present="yes"/> to the libvirt config. Using the qemu installed with Ubuntu 19.10 (version 4.0.0), I can reproduce the slowness by explicitly adding kernel_irqchip=off. Details: - Host CPU: Ryzen 3950X (16 core, 32 thread) - Host RAM: 64 GiB - Host OS: Ubuntu 19.10 64-bit, kernel version 5.5.0-rc4 (commit 738d2902773e + ACS override patch) - Guest CPU: host-passthrough, 16 vcpus (8 cores, 2 threads, topoext). - Guest RAM: 12 GiB - Guest machine type: pc-i440fx-4.0 (BIOS boot) - Guest OS: Windows Server 2016, build 1607 -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1851972 Title: pc-q35-4.1 and AMD Navi 5700/XT incompatible Status in QEMU: New Bug description: Hello, I am not sure if this qualifies as a "bug"; it is be more of an unknown issue with default settings. However, since the default value of q35 default_kernel_irqchip_split was changed seemingly due to similar user feedback, I thought this was important to share.. AMD Navi 5700/XT vfio-pci passthrough seems incompatible with one/multiple settings in pc-q35-3.1 and higher. The workaround for me is that pc-q35-3.0 still works fine passing through the GPU and official drivers can load/install fine. The default/generic GPU drivers in a Fedora 30 or Windows 1903 guest do work; the monitor displays the desktop in a 800x600 resolution and things are rendered fine.. so the basic functionality of the card seems fine with pc-q35-4.1. But attempting to use the official open source AMD driver with the card resulted in a hung kernel for the Fedora 30 guest.. and a BSOD on the Windows 1903 guest immediately during driver install. I do not see any errors in Qemu command output.. did not investigate other logs or KVM etc, because I am not sure what to look for or how to go about it. Also not sure which combination of the latest q35 default settings are valid combinations to try either, because it seems that multiple things have changed related to pcie-root-port defaults and other machine options. I am happy to run tests and provide feedback if that helps identify the issue. I am using "Linux arch 5.4.0-rc6-mainline" kernel on ArchLinux host with AMD Navi reset pci quirk patch applied. My working Qemu command line is this: QEMU_AUDIO_DRV=pa \ QEMU_PA_SERVER=/run/user/1000/pulse/native \ /usr/bin/qemu-system-x86_64 \ -name windows \ -m 16g \ -accel kvm \ -machine pc-q35-3.0,accel=kvm,pflash0=ovmf0,pflash1=ovmf1 \ -blockdev node-name=ovmf0,driver=file,filename=/virt/qemu/roms/OVMF_CODE.fd,read-only=on \ -blockdev node-name=ovmf1,driver=file,filename=/virt/qemu/machines/windows/OVMF_VARS.fd \ -boot menu=on \ -global kvm-pit.lost_tick_policy=discard \ -no-hpet \ -rtc base=utc,clock=host,driftfix=slew \ -cpu host,kvm=off,hv_vendor_id=RedHatRedHat,hv_spinlocks=0x1fff,hv_vapic,hv_time,hv_reset,hv_vpindex,hv_runtime,hv_relaxed,hv_synic,hv_stimer \ -smp sockets=1,cores=4,threads=1 \ -nodefaults \ -netdev bridge,br=br0,id=net0 \ -device virtio-net-pci,netdev=net0,addr=19.0,mac=52:54:00:12:34:77 \ -device virtio-scsi-pci \ -blockdev raw,node-name=disk0,cache.direct=off,discard=unmap,file.driver=file,file.aio=threads,file.filename=/virt/qemu/machines/windows/os.raw \ -device scsi-hd,drive=disk0,rotation_rate=1 \ -blockdev raw,node-name=disk1,cache.direct=off,discard=unmap,file.driver=file,file.aio=threads,file.filename=/virt/qemu/machines/windows/data.raw \ -device scsi-hd,drive=disk1,rotation_rate=1 \ -drive index=0,if=ide,media=cdrom,readonly,file=/virt/qemu/isos/Win10_1903_V2_English_x64.iso \ -drive index=1,if=ide,media=cdrom,readonly,file=/virt/qemu/isos/virtio-win-0.1.173.iso \ -device ich9-intel-hda,addr=1b.0 \ -device hda-output \ -monitor stdio \ -display none \ -vga none \ -device pcie-root-port,id=pcierp0,chassis=1,slot=1,addr=1c.0,disable-acs=on,multifunction=on \ -device pcie-root-port,id=pcierp1,chassis=2,slot=2,addr=1c.1,disable-acs=on \ -device x3130-upstream,bus=pcierp0,id=pcieu0 \ -device xio3130-downstream,bus=pcieu0,id=pcied0,chassis=11,slot=11 \ -device vfio-pci,host=03:00.0,bus=pcied0,addr=00.0,multifunction=on \ -device vfio-pci,host=03:00.1,bus=pcied0,addr=00.1 \ -device qemu-xhci,addr=1d.0 \ -device usb-host,vendorid=0x258a,productid=0x0001 \ -device usb-host,vendorid=0x1bcf,productid=0x0005 ; Thank you! To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1851972/+subscriptions
