Yuanyuan Zhao 0a4c76357e hv: hide mwait from guest. ...

When CPU support MONITOR/MWAIT, OS prefer to use it enter
deeper C-state.

Now ACRN pass through MONITOR/MWAIT to guest.

For vCPUs (ie vCPU A and vCPU B) share a pCPU, if vCPU A uses MWait to enter C state,
vCPU B could run only after the time slice of vCPU A is expired. This time slice of
vCPU A is gone to waste.

For Local APIC pass-through (used for RTVM), the guest pay more attention to
timeliness than power saving.

So this patch hides MONITOR/MWAIT by:
    1. Clear vCPUID.05H, vCPUID.01H:ECX.[bit 3] and
    MSR_IA32_MISC_ENABLE_MONITOR_ENA to tell the guest VM's vCPU
    does not support MONITOR/MAIT.
    2. Enable MSR_IA32_MISC_ENABLE_MONITOR_ENA bit for
    MSR_IA32_MISC_ENABLE inject 'GP'.
    3. Trap instruction 'MONITOR' and 'MWAIT' and inject 'UD'.
    4. Clear vCPUID.07H:ECX.[bit 5] to hide 'UMONITOR/UMWAIT'.
    5. Clear  "enable user wait and pause" VM-execution control, so
    UMONITOR/MWAIT causes an 'UD'.

Tracked-On: #8253
Signed-off-by: Yuanyuan Zhao <yuanyuan.zhao@linux.intel.com>
Reviewed-by: Fei Li <fei1.li@intel.com>

2022-11-04 18:55:52 +08:00

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