> > Here's an explanation of the physical address reduction for bare-metal and > guest. > > With MSR 0xC001_0010[SMEE] = 0: > No reduction in host or guest max physical address. > > With MSR 0xC001_0010[SMEE] = 1: > - Reduction in the host is enumerated by CPUID 0x8000_001F_EBX[11:6], > regardless of whether SME is enabled in the host or not. So, for example > on EPYC generation 2 (Rome) you would see a reduction from 48 to 43. > - There is no reduction in physical address in a legacy guest (non-SEV > guest), so the guest can use a 48-bit physical address > - There is a reduction of only the encryption bit in an SEV guest, so > the guest can use up to a 47-bit physical address. This is why the > Qemu command line sev-guest option uses a value of 1 for the > "reduced-phys-bits" parameter. > The guest statements all assume that NPT is enabled. Thanks, Tom
