Re: [PATCH] x86/sev: Don't use cc_platform_has() for early SEV-SNP calls

[Borislav Petkov]

On Wed, Aug 24, 2022 at 11:43:10AM -0700, Dave Hansen wrote:
> So, we don't have *ANY* control over where the compiler uses jump
> tables.  The kernel just happened to add some code that uses them, fell
> over, and this adds a hack to get booting again.
> 
> Isn't this a bigger problem?

I had the same question already. Was thinking of maybe disabling
the compiler from producing jump tables in the ident-mapped code.
Tom's argument is that that might prevent the compiler from doing
optimizations but I haven't talked to compiler folks whether those
optimizations are even worth the effort.

Regardless, the potential problem is limited:

"# (jump-tables are implicitly disabled by RETPOLINE)"

i.e., only RETPOLINE=n builds for now which should be a minority?

I guess when this explodes somewhere else again, we will have to
generalize a fix.

Thx.

-- 
Regards/Gruss,
    Boris.

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