Messages in this thread | | | Date | Mon, 25 Mar 2019 18:32:39 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH 1/3] kexec: Do not map the kexec area as decrypted when SEV is active |
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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@zn.tnic
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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