UefiCpuPkg CpuCommFeaturesLib: Reduce to set MSR_IA32_CLOCK_MODULATION

BZ: https://bugzilla.tianocore.org/show_bug.cgi?id=1810

This patch covers two problems.

1. Current code gets CPUID_THERMAL_POWER_MANAGEMENT in
ClockModulationInitialize() and uses its ECMD bit for all processors.
But ClockModulationInitialize() is only executed by BSP, that means
the bit is just for BSP.
It may have no functionality issue as all processors may have same
bit value in a great possibility. But for good practice, the code
should get CPUID_THERMAL_POWER_MANAGEMENT in ClockModulationSupport
(executed by all processors), and then use them in
ClockModulationInitialize() for all processors.
We can see that Aesni.c (and others) have used this good practice.

2. Current code uses 3 CPU_REGISTER_TABLE_WRITE_FIELD for
MSR_IA32_CLOCK_MODULATION in ClockModulationInitialize(), they can
be reduced to 1 CPU_REGISTER_TABLE_WRITE64 by getting
MSR_IA32_CLOCK_MODULATION for all processors in
ClockModulationSupport() and then update fields for register table
write in ClockModulationInitialize().

We may argue that there may be more times of MSR_IA32_CLOCK_MODULATION
getting. But actually the times of MSR_IA32_CLOCK_MODULATION getting
could be also reduced.

The reason is in ProgramProcessorRegister() of CpuFeaturesInitialize.c,
AsmMsrBitFieldWrite64 (AsmReadMsr64 + AsmWriteMsr64) will be used for
CPU_REGISTER_TABLE_WRITE_FIELD, and AsmWriteMsr64 will be used for
CPU_REGISTER_TABLE_WRITE64.

The times of MSR accessing could be reduced with this patch.
Without the patch:
3 CPU_REGISTER_TABLE_WRITE_FIELD (in ClockModulationInitialize)
  ==> 3 AsmMsrBitFieldWrite64
    ==> 3 AsmReadMsr64 + 3 AsmWriteMsr64

With the patch:
1 AsmReadMsr64 (in ClockModulationSupport) +
1 CPU_REGISTER_TABLE_WRITE64 (in ClockModulationInitialize)
  ==> 1 AsmWriteMsr64

Cc: Laszlo Ersek <lersek@redhat.com>
Cc: Eric Dong <eric.dong@intel.com>
Cc: Ray Ni <ray.ni@intel.com>
Cc: Chandana Kumar <chandana.c.kumar@intel.com>
Cc: Kevin Li <kevin.y.li@intel.com>
Signed-off-by: Star Zeng <star.zeng@intel.com>
Reviewed-by: Ray Ni <ray.ni@intel.com>

0 files changed, 0 insertions, 0 deletions