hvf: RDTSCP capability not passed to guests

Host environment

• Operating system: macOS Monterey 12.3.1
• OS/kernel version: 21E258
• Architecture: x86_64
• QEMU flavor: qemu-system-x86_64
• QEMU version: 6.2.0, master
• QEMU command line:

  ./qemu-system-x86_64 -cpu host,+rdtscp -machine q35,accel=hvf -m 512 -cdrom ./alpine-standard-3.15.4-x86.iso

Emulated/Virtualized environment

• Operating system: Alpine 3.15.4
• OS/kernel version: 5.15.32-0-virt #1-Alpine SMP
• Architecture: x86_64

Description of problem

Steps to reproduce

1. Run: wget https://dl-cdn.alpinelinux.org/alpine/v3.15/releases/x86/alpine-standard-3.15.4-x86.iso ./qemu-system-x86_64 -cpu host,+rdtscp -machine q35,accel=hvf -m 512 -cdrom ./alpine-standard-3.15.4-x86.iso

2. login as "root"

3. type

cat /etc/cpuinfo | grep rdtscp

Expected result: cpu flag lines including rdtscp Actual result: empty, with:

warning: host doesn't support requested feature: CPUID.80000001H:EDX.rdtscp [bit 27]

Additional information

This patch apparently resolves the issue according to my tests:

https://lore.kernel.org/qemu-devel/20211101054836.21471-1-dirty@apple.com/