* Andi Kleen <a...@firstfloor.org> wrote:
> From: Andi Kleen <a...@linux.intel.com>
>
> The AMD K6 errata check relies on timing a indirect call.
> But the way it was written it could be optimized to a direct call.
> Force gcc to actually do a indirect call and not just
> constant resolve the target address.
>
> Signed-off-by: Andi Kleen <a...@linux.intel.com>
>
> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
> index 4a549db..11ea6f6 100644
> --- a/arch/x86/kernel/cpu/amd.c
> +++ b/arch/x86/kernel/cpu/amd.c
> @@ -115,7 +115,7 @@ static void __cpuinit init_amd_k6(struct cpuinfo_x86 *c)
> */
>
> n = K6_BUG_LOOP;
> - f_vide = vide;
> + asm("" : "=g" (f_vide) : "0" (vide));
> rdtscl(d);
> while (n--)
> f_vide();
Would be useful to read in the changelog about how you found the bug:
- saw miscalculated values and figured out the reason
- saw a new warning in GCC
- saw it during review
?
Ingo
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