On Thu, Sep 22, 2016 at 02:49:22PM -0500, Tom Lendacky wrote:
> > I thought that reduction is the reservation of bits for the SME mask.
> >
> > What other reduction is there?
>
> There is a reduction in physical address space for the SME mask and the
> bits used to aid in identifying the ASID associated with the memory
> request. This allows for the memory controller to determine the key to
> be used for the encryption operation (host/hypervisor key vs. an SEV
> guest key).
Ok, I think I see what you mean: you call SME mask the bit in CPUID
Fn8000_001F[EBX][5:0], i.e., the C-bit, i.e. sme_me_mask. And the other
reduction is the key ASID, i.e., CPUID Fn8000_001F[EBX][11:6], i.e.
sme_me_loss.
I think we're on the same page - I was simply calling everything SME
mask because both are together in the PTE:
"Additionally, in some implementations, the physical address size of the
processor may be reduced when memory encryption features are enabled,
for example from 48 to 43 bits."
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
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