On 3/7/2025 12:22 AM, Zhao Liu wrote:
Hi Xiaoyao,
First, it's not a good practice that values in env->features[] cannot be
directly used for guest CPUID in void cpu_x86_cpuid(), but require further
adjustment there. env->features[] are supposed to be finalized at cpu
realization, so that after it env->features[] is reliable.
Second, there is one dependency entry relates to CPUID_EXT_PDCM in
feature_dependencies[]. QEMU needs to get correct value of
CPUID_EXT_PDCM in env->features[] to ensure applying the dependencies
correctly.
I agree that this is a very good idea, especially since PDCM has a
dependency entry.
"pmu" is totally a property rather than a feature bit, which makes the
dependency relationships in the code complex. Therefore, I think it's
worth having a series to clarify the dependencies of pmu as much as
possible.
I remember Dapeng/Zide also have fixes for pmu dependencies, and if
possible, I could help you combine this series with others' cleanups.
The reason I sent out this small series quickly is mainly for Dongli to
as a reference.
In fact, there are mess on LBR enabling that it checks enable_pmu
everytime with CPUID_7_0_EDX_ARCH_LBR as well as
CPUID_8000_0022_EAX_PERFMON_V2. That's on my WIP list to clean it up.
I think I need to check if they are duplicated with Dapeng/Zide's series.
Additionally, I think patch 1 and patch 2 can be merged together. Do you
agree?
IMHO, they stand as their own. I'll leave it to Paolo to make the decision.
Thanks,
Zhao
