x86: Don't rely on VMWare emulating PAT MSR correctly

x86: Don't rely on VMWare emulating PAT MSR correctly

VMWare seems not to emulate the PAT MSR correctly: reaeding
MSR_IA32_CR_PAT returns 0 even after writing another value to it.

Commit bd809af16e3ab triggers this VMWare bug when the kernel is
booted as a VMWare guest.

Detect this bug and don't use the read value if it is 0.

Fixes: bd809af16e3ab "x86: Enable PAT to use cache mode translation tables"
Reported-and-tested-by: Jongman Heo <[email protected]>
Acked-by: Alok N Kataria <[email protected]>
Signed-off-by: Juergen Gross <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Thomas Gleixner <[email protected]>