On Mon, Mar 25, 2019 at 05:17:55PM +0000, Singh, Brijesh wrote:
> By default all the memory regions are mapped encrypted. The
> set_memory_{encrypt,decrypt}() is a generic function which can be
> called explicitly to clear/set the encryption mask from the existing
> memory mapping. The mem_encrypt_active() returns true if either SEV or
> SME is active. So the __set_memory_enc_dec() uses the
> memory_encrypt_active() check to ensure that the function is no-op when
> SME/SEV are not active.
>
> Currently, the arch_kexec_post_alloc_pages() unconditionally clear the
> encryption mask from the kexec area. In case of SEV, we should not clear
> the encryption mask.
Brijesh, I know all that.
Please read what I said here at the end:
https://lkml.kernel.org/r/20190324150034.GH23289@xxxxxxx
With this change, the code looks like this:
+ if (sme_active())
+ return set_memory_decrypted((unsigned long)vaddr, pages);
now in __set_memory_enc_dec via set_memory_decrypted():
/* Nothing to do if memory encryption is not active */
if (!mem_encrypt_active())
return 0;
so you have:
if (sme_active())
...
if (!mem_encrypt_active())
now maybe this is all clear to you and Tom but I betcha others will get
confused. Probably something like "well, what should be active now, SME,
SEV or memory encryption in general"?
I hope you're catching my drift.
So if you want to *not* decrypt memory in the SEV case, then doing something
like this should make it a bit more clear:
if (sev_active())
return;
return set_memory_decrypted((unsigned long)vaddr, pages);
along with a comment *why* we're checking here.
But actually, I'd prefer if you had separate wrappers which are called
for SME and for SEV.
I'll let Tom chime in too.
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
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