On 1/12/23 10:55, Michael Brown wrote: > On 12/01/2023 08:28, Laszlo Ersek wrote: >> In QEMU v5.1.0, the CPU hotplug register block misbehaves: the >> negotiation >> protocol is (effectively) broken such that it suggests that switching >> from >> the legacy interface to the modern interface works, but in reality the >> switch never happens. The symptom has been witnessed when using TCG >> acceleration; KVM seems to mask the issue. The issue persists with the >> following (latest) stable QEMU releases: v5.2.0, v6.2.0, v7.2.0. >> Currently >> there is no stable release that addresses the problem. >> >> The QEMU bug confuses the Present and Possible counting in function >> PlatformMaxCpuCountInitialization(), in >> "OvmfPkg/Library/PlatformInitLib/Platform.c". OVMF ends up with Present=0 >> Possible=1. This in turn further confuses MpInitLib in UefiCpuPkg (hence >> firmware-time multiprocessing will be broken). Worse, CPU hot(un)plug >> with >> SMI will be summarily broken in OvmfPkg/CpuHotplugSmm, which (considering >> the privilege level of SMM) is not that great. >> >> Detect the issue in PlatformMaxCpuCountInitialization(), and print an >> error message and *hang* if the issue is present. > > Would this mean that OVMF would refuse to start with all current distro > versions of qemu (when not using KVM), or am I misunderstanding?
Your understanding is correct. I'm not in a rush to get this merged, but eventually, it should be. On qemu-devel, I asked for the fix to be applied to all stable branches starting with v5.*. I'm not sure how far "back" qemu-stable is maintained though. Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#98365): https://edk2.groups.io/g/devel/message/98365 Mute This Topic: https://groups.io/mt/96218818/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-
