I can't say I like the name. After all that should be the normal
case for a long time now ... native? normal? bareiron?

Also I would prefer if you split this file up a bit - the old
processor/system/irqflags split wasn't too bad.

+
+/*
+ * Set IOPL bits in EFLAGS from given mask
+ */
+static inline void set_iopl_mask(unsigned mask)

This function can be completely written in C using local_save_flags()/local_restore_flags()
Please do that. I guess it's still a good idea to keep it separated
though because it might allow other optimizations.

e.g. i've been thinking about special casing IF changes in save/restore flags 
to optimize CPUs which have slow pushf/popf. If you already make sure
all non IF manipulations of flags are separated that would help.

+/* Stop speculative execution */
+static inline void sync_core(void)
+{
+	unsigned int eax = 1, ebx, ecx, edx;
+	__cpuid(&eax, &ebx, &ecx, &edx);
+}

Actually I don't think this one should be para virtualized at all.
I don't see any reason at all why a hypervisor should trap it and it
is very time critical. I would recommend you move it back into the 
normal files without hooks.

+
+/*
+ * Clear and set 'TS' bit respectively
+ */

The comment seems out of date (no set TS)

+#define clts() __asm__ __volatile__ ("clts")
+#define read_cr0() ({ \
+	unsigned int __dummy; \
+	__asm__ __volatile__( \

Maybe it's just me, but can't you just drop all these __s around
asm and volatile? They are completely useless as far I know. 

Also the assembly will be easier readable if you just keep it on a single 
line for the simple ones.

-Andi