There is a bug in versions 2025-02-10 and later that causes virtual machines to be created with incorrect SMP settings with warnings about TCG features when setting more than 2 cores with the smp option in the default TCG acceleration (see main text).
Host environment
- Operating system: Windows
- OS/kernel version: n/a
- Architecture: x86_64
- QEMU flavor: qemu-system-x86_64
- QEMU version: 9.2.50 or later
- QEMU command line:
'qemu-system-x86_64 ... -smp n ... ' or
'qemu-system-x86_64 ... -smp sockets=1,cores=n,threads=1 ... '
- n is the number of cores to use
Emulated/Virtualized environment
- Operating system: Not applicable
- OS/kernel version: Not applicable
- Architecture: x86_64
Description of problem
When using qemu-system-x86_64 in versions 9.2.50 and later, if you create a virtual machine with 2 or more cores using the smp option,
qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]
qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.cmp-legacy [bit 1]The log will be displayed as many as the number of cores you have enabled, and the created virtual machine will be displayed as having a 1-core CPU with the number of cores you have enabled.
- I have not tested whether the same symptom occurs on versions 9.2.50 and later for other environments (Linux and the WoA version released on March 26th).
Steps to reproduce
- Create a virtual machine with more than two cores using TCG acceleration, which is the default acceleration, by using options such as 'qemu-system-x86_64 -smp 2' or 'qemu-system-x86_64 -smp sockets=1,cores=2,threads=1'.
- 'qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.01H:EDX.ht [bit 28]' and 'qemu-system-x86_64: warning: TCG doesn't support requested feature: CPUID.80000001H:ECX.cmp-legacy [bit 1]' The log is generated as many as the number of cores set and the virtual machine is created.
- When checking the CPU information of the booted virtual machine, it does not show that there is one CPU with the specified number of cores, but rather that there is a single core CPU with the specified number of cores.
Additional information
>qemu-system-x86_64 -M q35 -smp 2 -m 4g -display sdl -usb -device usb-tablet -drive file=MasterOS.vdi,id=disk,if=none -drive file="C:\Program Files\qemu\share\edk2-x86_64-code.fd",id=efi,readonly=on,format=raw,if=pflash -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.1 -rtc base=localtime
>qemu-system-x86_64 -M q35 -smp 4 -m 4g -display sdl -usb -device usb-tablet -drive file=MasterOS.vdi,id=disk,if=none -drive file="C:\Program Files\qemu\share\edk2-x86_64-code.fd",id=efi,readonly=on,format=raw,if=pflash -device ahci,id=ahci -device ide-hd,drive=disk,bus=ahci.1 -rtc base=localtime