x86/mm: Redefine some of page table helpers as macros

This is preparation for the next patch, which would change
pgtable_l5_enabled to be cpu_feature_enabled(X86_FEATURE_LA57).

The change makes few helpers in paravirt.h dependent on
cpu_feature_enabled() definition from cpufeature.h.
And cpufeature.h is dependent on paravirt.h.

Let's re-define some of helpers as macros to break this dependency loop.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Borislav Petkov <bp@suse.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-mm@kvack.org
Link: http://lkml.kernel.org/r/20180216114948.68868-3-kirill.shutemov@linux.intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/include/asm/paravirt.h

@@ -567,19 +567,22 @@ static inline p4dval_t p4d_val(p4d_t p4d)
 	return PVOP_CALLEE1(p4dval_t, pv_mmu_ops.p4d_val, p4d.p4d);
 }
 
-static inline void set_pgd(pgd_t *pgdp, pgd_t pgd)
+static inline void __set_pgd(pgd_t *pgdp, pgd_t pgd)
 {
-	if (pgtable_l5_enabled)
-		PVOP_VCALL2(pv_mmu_ops.set_pgd, pgdp, native_pgd_val(pgd));
-	else
-		set_p4d((p4d_t *)(pgdp), (p4d_t) { pgd.pgd });
+	PVOP_VCALL2(pv_mmu_ops.set_pgd, pgdp, native_pgd_val(pgd));
 }
 
-static inline void pgd_clear(pgd_t *pgdp)
-{
-	if (pgtable_l5_enabled)
-		set_pgd(pgdp, __pgd(0));
-}
+#define set_pgd(pgdp, pgdval) do {					\
+	if (pgtable_l5_enabled)						\
+		__set_pgd(pgdp, pgdval);				\
+	else								\
+		set_p4d((p4d_t *)(pgdp), (p4d_t) { (pgdval).pgd });	\
+} while (0)
+
+#define pgd_clear(pgdp) do {						\
+	if (pgtable_l5_enabled)						\
+		set_pgd(pgdp, __pgd(0));				\
+} while (0)
 
 #endif  /* CONFIG_PGTABLE_LEVELS == 5 */