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Date:   Fri, 1 Jul 2022 18:51:13 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Sean Christopherson <seanjc@google.com>
Cc:     Tom Lendacky <thomas.lendacky@amd.com>,
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Subject: Re: [PATCH v12 19/46] x86/kernel: Make the .bss..decrypted section
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On Thu, Jun 16, 2022 at 04:41:05PM +0000, Sean Christopherson wrote:
> > I worry that another use of cc_platform_has() could creep in at some point
> > and cause the same issue. Not sure how bad it would be, performance-wise, to
> > remove the jump table optimization for arch/x86/coco/core.c.

Is there a gcc switch for that?

> One thought would be to initialize "vendor" to a bogus value, disallow calls to
> cc_set_vendor() until after the kernel as gotten to a safe point, and then WARN
> (or panic?) if cc_platform_has() is called before "vendor" is explicitly set.
> New calls can still get in, but they'll be much easier to detect and less likely
> to escape initial testing.

The invalid vendor thing makes sense but I don't think it'll help in
this case.

We set vendor in sme_enable() which comes before the

__startup_64 -> sme_postprocess_startup

path you're hitting.

We could do only the aspect of checking whether it hasn't been set yet
and warn then, in order to make the usage more robust...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette