Re: [PATCH v8 06/40] x86/sev: Check SEV-SNP features support

[Borislav Petkov]

On Thu, Dec 16, 2021 at 10:28:45AM -0600, Brijesh Singh wrote:
> A good question; the GHCB page is needed only at the time of #VC.  If the
> second stage VC handler is not called after the sev_enable() during the
> decompression stage, setting up the GHC page in sev_enable() is a waste.

It would be a waste if no #VC would fire. But we set up a #VC handler so
we might just as well set up the GHCB for it too.

> But in practice, the second stage VC handler will be called during
> decompression. It also brings a similar question for the kernel
> proper, should we do the same over there?

I'd think so, yes.
 
> Jorge did the initial ES support and may have other reasons he chose to set
> up GHCB page in the handler. I was trying to avoid the flow change. We can
> do this as a pre or post-SNP patch; let me know your thoughts?

You can do a separate patch only with that change and if it causes
trouble, we can always debug/delay it.

Thx.

-- 
Regards/Gruss,
    Boris.

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