Messages in this thread | | | Date | Fri, 12 Aug 2022 16:33:09 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v2 1/2] x86/sev: Put PSC struct on the stack in prep for unaccepted memory support |
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On Fri, Aug 12, 2022 at 09:11:25AM -0500, Tom Lendacky wrote: > There was a whole discussion on this
Pointer to it?
> and I would prefer to keep the ability to parallelize PSC without > locking.
So smaller, on-stack PSC but lockless is still better than a bigger one but with synchronized accesses to it?
> Well when we don't know which GHCB is in use, using that reserved area in > the GHCB doesn't help.
What do you mean?
The one which you read with
data = this_cpu_read(runtime_data);
in snp_register_per_cpu_ghcb() is the one you register.
> Also, I don't want to update the GHCB specification for a single bit > that is only required because of the way Linux went about establishing > the GHCB usage.
Linux?
You mean, you did it this way: 885689e47dfa1499b756a07237eb645234d93cf9
:-)
"The runtime handler needs one GHCB per-CPU. Set them up and map them unencrypted."
Why does that handler need one GHCB per CPU?
As to the field, I was thinking along the lines of
struct ghcb.vendor_flags
field which each virt vendor can use however they like.
It might be overkill but a random bool ain't pretty either. Especially if those things start getting added for all kinds of other things.
If anything, you could make this a single u64 sev_flags which can at least collect all that gunk in one variable ... at least...
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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