Ran through the commits included in the audio code merge, with the following results:
[commit 280c1e1cdb24d80ecdfcdfc679ccc5e8ed7af45d] audio/hda: create millisecond timers that handle IO Audio stream gets progressively more and more corrupted, breaking completely between 30'' and 1' after continuous sound start. No problems playing short sounds. -- [commit 0a373bb310c1533e24aa5e3edbf206507fb342ea] audio/hda: turn some dprintfs into trace points No changes from the previous commit, of course. -- [commit 8ced0669237b2bbedac3e4ce6fcf7aaaafaae663] audio/hda: tweak timer adjust logic First time audio looks really good on this guest; the new code is working, by the look of things. -- [commit 4501ee16c76e89e0a2b2beb95f3b93f965997391] audio/hda: detect output buffer overruns First time issue presents itself. -- So, I assume that commit 4501ee16c76e89e0a2b2beb95f3b93f965997391 introduced some kind of overrun control which mishandles the buffer, at least in my setup. >From a quick and ignorant git diff between this and the previous commit, I can >see that the new detector could drop the buffer too early, or maybe it >misconfigures the st->buft_start property. These last tests were performed by manually toggling the use-timer property on from inside the source code; I hope this doesn't invalidate their outcome, though. As of now I have no clue on how to patch this thing, since I do not understand the interactions between the various emulator's components. -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1795527 Title: Malformed audio and video output stuttering after upgrade to QEMU 3.0 Status in QEMU: New Bug description: My host is an x86_64 Arch Linux OS with a recompiled 4.18.10 hardened kernel, running a few KVM guests with varying OSes and configurations managed through a Libvirt stack. Among these guests I have two Windows 10 VMs with VGA passthrough and PulseAudio-backed virtual audio devices. After upgrading to QEMU 3.0.0, both of the Win10 guests started showing corrupted audio output in the form of unnatural reproduction speed and occasional but consistently misplaced audio fragments originating from what seems to be a circular buffer wrapping over itself (misbehaviour detected by starting some games with known OSTs and dialogues: soundtracks sound accelerated and past dialogue lines start replaying middle-sentence until the next line starts playing). In addition, the video output of the malfunctioning VMs regularly stutters roughly twice a second for a fraction of a second (sync'ed with the suspected buffer wrapping and especially pronounced during not-pre-rendered cutscenes), toghether with mouse freezes that look like actual input misses more than simple lack of screen refreshes. The issue was succesfully reproduced without the managing stack, directly with the following command line, on the most capable Windows guest: QEMU_AUDIO_DRV=pa QEMU_PA_SERVER=127.0.0.1 /usr/bin/qemu-system-x86_64 -name guest=win10_gms,debug-threads=on \ -machine pc-i440fx-3.0,accel=kvm,usb=off,vmport=off,dump-guest-core=off \ -cpu host,hv_time,hv_relaxed,hv_vapic,hv_spinlocks=0x1fff,hv_vendor_id=123456789abc,kvm=off \ -drive file=/usr/share/ovmf/x64/OVMF_CODE.fd,if=pflash,format=raw,unit=0,readonly=on \ -drive file=/var/lib/libvirt/qemu/nvram/win10_gms_VARS.fd,if=pflash,format=raw,unit=1 \ -m 5120 \ -realtime mlock=off \ -smp 3,sockets=1,cores=3,threads=1 \ -uuid 39b56ee2-6bae-4009-9108-7be26d5d63ac \ -display none \ -no-user-config \ -nodefaults \ -rtc base=localtime,driftfix=slew \ -global kvm-pit.lost_tick_policy=delay \ -no-hpet \ -no-shutdown \ -global PIIX4_PM.disable_s3=1 \ -global PIIX4_PM.disable_s4=1 \ -boot strict=on \ -device ich9-usb-ehci1,id=usb,bus=pci.0,addr=0x4.0x7 \ -device ich9-usb-uhci1,masterbus=usb.0,firstport=0,bus=pci.0,multifunction=on,addr=0x4 \ -device ich9-usb-uhci2,masterbus=usb.0,firstport=2,bus=pci.0,addr=0x4.0x1 \ -device ich9-usb-uhci3,masterbus=usb.0,firstport=4,bus=pci.0,addr=0x4.0x2 \ -device ahci,id=sata0,bus=pci.0,addr=0x9 \ -drive file=/dev/vms/win10_gaming,format=raw,if=none,id=drive-virtio-disk0,cache=none,aio=native \ -device virtio-blk-pci,scsi=off,bus=pci.0,addr=0x5,drive=drive-virtio-disk0,id=virtio-disk0,bootindex=1,write-cache=on \ -drive file=/dev/sr0,format=raw,if=none,id=drive-sata0-0-0,media=cdrom,readonly=on \ -device ide-cd,bus=sata0.0,drive=drive-sata0-0-0,id=sata0-0-0 \ -device intel-hda,id=sound0,bus=pci.0,addr=0x3 \ -device hda-duplex,id=sound0-codec0,bus=sound0.0,cad=0 \ -device usb-host,hostbus=2,hostaddr=3,id=hostdev0,bus=usb.0,port=1 \ -device vfio-pci,host=01:00.0,id=hostdev1,bus=pci.0,addr=0x6 \ -device vfio-pci,host=01:00.1,id=hostdev2,bus=pci.0,addr=0x7 \ -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x8 \ -sandbox on,obsolete=deny,elevateprivileges=deny,spawn=deny,resourcecontrol=deny \ -msg timestamp=on By "purposedly misconfiguring" the codepaths and replacing "pc-i440fx-3.0" with "pc-i440fx-2.11" (basically reverting the config changes I needed to do in order to update the domain definitions), the stuttering seems to disappear (or at least becomes negligible) and the audio output, despite becoming incredibly distorted, is consistent in every other way, with in-order dialogues and (perceived) correct tempo. In order to exclude eventual misconfigurations in the host's audio processing pipeline, I proceeded to update the domain definition's codepath of another guest running Ubuntu 18.04 with a completely different hardware configuration (no video card passthrough and no PulseAudio backconnection, just a plain emulated VirtIO display and Spice audio device). The audio issue presented itself again in the form of slightly sped up audio playback from Internet videos interleaved with occasional "quenches" of playing speed. Stutters are difficult to detect because of the poor refresh rate of the emulated VGA adapter, but I wouldn't be surprised to find them here too (actually, I *think* I sensed them, but I'm not sure enough to assess their existence). Once again, by reverting to the old 2.11 directive everything is back to normal. Given the fact that no official upgrade directives regarding required sampling rate, period or sheduling adjustments were stated or handed-out to administrators, I decided to report this behaviour as a bug. I hope this is the appropriate channel and that I didn't annoy anyone (this is my first proper bug report, please forgive me for any innaccuracy). To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1795527/+subscriptions
