On 5/28/2024 2:23 AM, Igor Mammedov wrote:
> On Fri, 24 May 2024 13:00:14 -0700
> Zide Chen <zide.c...@intel.com> wrote:
>
>> Currently, if running "-overcommit cpu-pm=on" on hosts that don't
>> have MWAIT support, the MWAIT/MONITOR feature is advertised to the
>> guest and executing MWAIT/MONITOR on the guest triggers #UD.
>
> this is missing proper description how do you trigger issue
> with reproducer and detailed description why guest sees MWAIT
> when it's not supported by host.
If "overcommit cpu-pm=on" and "-cpu hpst" are present, as shown in the
following, CPUID_EXT_MONITOR is set after x86_cpu_filter_features(), so
that it doesn't have a chance to check MWAIT against host features and
will be advertised to the guest regardless of whether it's supported by
the host or not.
x86_cpu_realizefn()
x86_cpu_filter_features()
cpu_exec_realizefn()
kvm_cpu_realizefn
host_cpu_realizefn
host_cpu_enable_cpu_pm
env->features[FEAT_1_ECX] |= CPUID_EXT_MONITOR;
If it's not supported by the host, executing MONITOR or MWAIT
instructions from the guest triggers #UD, no matter MWAIT_EXITING
control is set or not.
