For reason that,
The turbo frequency info depends on specific machine type. And the msr
value of MSR_PLATFORM_INFO may be diferent on diffrent generation machine.
Get following msr bits (needed by turbostat on intel platform) by rdmsr
MSR_PLATFORM_INFO directly in KVM is more reasonable. And set these msr
bits as vcpu->arch.msr_platform_info default value.
-bit 15:8, Maximum Non-Turbo Ratio (MAX_NON_TURBO_LIM_RATIO)
-bit 47:40, Maximum Efficiency Ratio (MAX_EFFICIENCY_RATIO)
On 2023/8/21 15:52, Chao Gao wrote:
On Mon, Aug 21, 2023 at 11:26:32AM +0800, Hao Xiang wrote:
For intel platform, The BzyMhz field of Turbostat shows zero
due to the missing of part msr bits of MSR_PLATFORM_INFO.
Acquire necessary msr bits, and expose following msr info to guest,
to make sure guest can get correct turbo frequency info.
Userspace VMM (e.g., QEMU) can configure this MSR for guests. Please refer to
tools/testing/selftests/kvm/x86_64/platform_info_test.c.
The question is why KVM needs this patch given KVM already provides interfaces
for QEMU to configure the MSR.
