[PATCH] x86: Fix for cache computation on AMD legacy cpus.

[Florian Weimer]

* sajan karumanchi:

> From: Sajan Karumanchi <sajan.karumanchi@amd.com>
>
> Some legacy AMD CPUs and hypervisors have the _cpuid_ '0x8000_001D'
> set to Zero, thus resulting in zeroed-out computed cache values.
> This patch reintroduces the old way of cache computation as a
> failsafe option to handle these exceptions.
>
> Reviewed-by: Premachandra Mallappa <premachandra.mallappa@amd.com>

Thanks.  On “AMD Turion(tm) II Neo N40L Dual-Core Processor”, this
fixes the regression.  The reported cache sizes are identical.

There's still one remaining issue (not a regression):

x86.cpu_features.level4_cache_size=0xffffffffffffffff

I think this should be zero if there is no L4 cache.

I'm going to test more machines early next week.