x86, cpu, amd: Fix crash as Xen Dom0 on AMD Trinity systems

f7f286a910221 ("x86/amd: Re-enable CPU topology extensions in case BIOS
has disabled it") wrongfully added code which used the AMD-specific
{rd,wr}msr variants for no real reason.

This caused boot panics on xen which wasn't initializing the
{rd,wr}msr_safe_regs pv_ops members properly.

This, in turn, caused a heated discussion leading to us reviewing all
uses of the AMD-specific variants and removing them where unneeded
(almost everywhere except an obscure K8 BIOS fix, see 6b0f43ddfa358).

Finally, this patch switches to the standard {rd,wr}msr*_safe* variants
which should've been used in the first place anyway and avoided unneeded
excitation with xen.

Signed-off-by: Andre Przywara <andre.przywara@amd.com>
Link: http://lkml.kernel.org/r/1338562358-28182-4-git-send-email-bp@amd64.org
Cc: Andreas Herrmann <andreas.herrmann3@amd.com>
Link: <http://lkml.kernel.org/r/1338383402-3838-1-git-send-email-andre.przywara@amd.com>
[Boris: correct and expand commit message]
Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: H. Peter Anvin <hpa@zytor.com>

arch/x86/kernel/cpu/amd.c

@@ -586,9 +586,9 @@ static void __cpuinit init_amd(struct cpuinfo_x86 *c)
 	    !cpu_has(c, X86_FEATURE_TOPOEXT)) {
 		u64 val;
 
-		if (!rdmsrl_amd_safe(0xc0011005, &val)) {
+		if (!rdmsrl_safe(0xc0011005, &val)) {
 			val |= 1ULL << 54;
-			wrmsrl_amd_safe(0xc0011005, val);
+			checking_wrmsrl(0xc0011005, val);
 			rdmsrl(0xc0011005, val);
 			if (val & (1ULL << 54)) {
 				set_cpu_cap(c, X86_FEATURE_TOPOEXT);