Re: [PATCH v10 06/50] x86/sev: Add the host SEV-SNP initialization support

[Kalra, Ashish]

Hello Jeremi,

> Hi Ashish,
>
> I just noticed that the kernel shouts at me about this bit when I offline->online a CPU in
> an SNP host:

Yes, i also observe the same warning when i bring a CPU back online.
> [2692586.589194] smpboot: CPU 63 is now offline
> [2692589.366822] [Firmware Warn]: MTRR: CPU 0: SYSCFG[MtrrFixDramModEn] not cleared by BIOS, clearing this bit
> [2692589.376582] smpboot: Booting Node 0 Processor 63 APIC 0x3f
> [2692589.378070] [Firmware Warn]: MTRR: CPU 63: SYSCFG[MtrrFixDramModEn] not cleared by BIOS, clearing this bit
> [2692589.388845] microcode: CPU63: new patch_level=0x0a0011d1
>
> Now I understand if you say "CPU offlining is not supported" but there's nothing currently
> blocking it.

There is CPU hotplug support for SNP platform to do __snp_enable() when 
bringing a CPU back online, but not really sure what needs to be done 
for MtrrFixDramModeEn bit in SYSCFG, discussing with the FW developers.

Thanks,
Ashish