Re: [Qemu-devel] [SeaBIOS] [PATCH v3] fw/msr_feature_control: add support to set MSR_IA32_FEATURE_CONTROL

[Paolo Bonzini]

> I've worried that if I only *call* these interfaces to set the MSR, then
> the next (independent) use of the same interfaces would clear the MSR
> through the INIT-SIPI-SIPI. That would have forced me to modify the
> protocol / PPI implementations so that any use of them would reprogram
> the MSR every time, after the INIT-SIPI-SIPI.
> 
> This way however (hopefully) it should suffice to call the PPI only --
> the results should survive from PEI to DXE to the runtime OS on the
> normal boot path, and from PEI to the runtime OS on the S3 resume path.

This is correct (for what I understand).  Out of curiosity, why is
it not enough to just add the MSR to the ACPI_CPU_DATA?  Or is it
what you're doing, but OVMF was not restoring MTRRs at S3 resume
time either?

Paolo