Sean Christopherson <seanjc@xxxxxxxxxx> writes: > On Fri, Aug 30, 2024, Vitaly Kuznetsov wrote: >> Gerd Hoffmann <kraxel@xxxxxxxxxx> writes: >> >> >> Necroposting! >> >> >> >> Turns out that this change broke "bochs-display" driver in QEMU even >> >> when the guest is modern (don't ask me 'who the hell uses bochs for >> >> modern guests', it was basically a configuration error :-). E.g: >> > >> > qemu stdvga (the default display device) is affected too. >> > >> >> So far, I was only able to verify that the issue has nothing to do with >> OVMF and multi-vcpu, it reproduces very well with >> >> $ qemu-kvm -machine q35,accel=kvm,kernel-irqchip=split -name guest=c10s >> -cpu host -smp 1 -m 16384 -drive file=/var/lib/libvirt/images/c10s-bios.qcow2,if=none,id=drive-ide0-0-0 >> -device ide-hd,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0,bootindex=1 >> -vnc :0 -device VGA -monitor stdio --no-reboot >> >> Comparing traces of working and broken cases, I couldn't find anything >> suspicious but I may had missed something of course. For now, it seems >> like a userspace misbehavior resulting in a segfault. > > Guest userspace? > Yes? :-) As Gerd described, video memory is "mapped into userspace so the wayland / X11 display server can software-render into the buffer" and it seems that wayland gets something unexpected in this memory and crashes. -- Vitaly
