On Thu, 9 May 2019 14:05:20 -0400
"Jason J. Herne" <jjherne@xxxxxxxxxxxxx> wrote:
[...]
> > +#define sme_me_mask 0ULL
> > +
> > +static inline bool sme_active(void) { return false; }
> > +extern bool sev_active(void);
> > +
>
> I noticed this patch always returns false for sme_active. Is it safe
> to assume that whatever fixups are required on x86 to deal with sme
> do not apply to s390?
yes, on x86 sev_active returns false if SEV is enabled. SME is for
host memory encryption. from arch/x86/mm/mem_encrypt.c:
bool sme_active(void)
{
return sme_me_mask && !sev_enabled;
}
and it makes sense because you can't have both SME and SEV enabled on
the same kernel, because either you're running on bare metal (and then
you can have SME) __or__ you are running as a guest (and then you can
have SEV). The key difference is that DMA operations don't need
bounce buffers with SME, but they do with SEV.
I hope this clarifies your doubts :)
[...]
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