Re: [PATCH v2] Linux VM workaround for Knights Landing A/D leak

[Borislav Petkov]

On Tue, Jun 14, 2016 at 11:54:24AM -0700, Dave Hansen wrote:
> Lukasz, Borislav suggested using static_cpu_has_bug(), which will do the
> alternatives patching.  It's definitely the right thing to use here.

Yeah, either that or do an

alternative_call(null_func, fix_pte_peak, X86_BUG_PTE_LEAK, ...)

or so and you'll need a dummy function to call on !X86_BUG_PTE_LEAK
CPUs.

The static_cpu_has_bug() thing should be most likely a penalty
of a single JMP (I have to look at the asm) but then since the
callers are inlined, you'll have to patch all those places where
*ptep_get_and_clear() get inlined.

Shouldn't be a big deal still but...

"debug-alternative" and a kvm guest should help you there to get a quick
idea.

HTH.

-- 
Regards/Gruss,
    Boris.

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