powerpc/mm: Fix lazy icache flush on pre-POWER5

On 64-bit CPUs with no-execute support and non-snooping icache, such as
970 or POWER4, we have a software mechanism to ensure coherency of the
cache (using exec faults when needed).

This was broken due to a logic error when the code was rewritten
from assembly to C, previously the assembly code did:

  BEGIN_FTR_SECTION
         mr      r4,r30
         mr      r5,r7
         bl      hash_page_do_lazy_icache
  END_FTR_SECTION(CPU_FTR_NOEXECUTE|CPU_FTR_COHERENT_ICACHE, CPU_FTR_NOEXECUTE)

Which tests that:
   (cpu_features & (NOEXECUTE | COHERENT_ICACHE)) == NOEXECUTE

Which says that the current cpu does have NOEXECUTE, but does not have
COHERENT_ICACHE.

Fixes: 91f1da99792a ("powerpc/mm: Convert 4k hash insert to C")
Fixes: 89ff725051d1 ("powerpc/mm: Convert __hash_page_64K to C")
Fixes: a43c0eb8364c ("powerpc/mm: Convert 4k insert from asm to C")
Cc: stable@vger.kernel.org # v4.5+
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
[mpe: Change log verbosification]
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

arch/powerpc/mm/hash64_4k.c

@@ -55,7 +55,7 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
 	 */
 	rflags = htab_convert_pte_flags(new_pte);
 
-	if (!cpu_has_feature(CPU_FTR_NOEXECUTE) &&
+	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
 	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);
 

arch/powerpc/mm/hash64_64k.c

@@ -87,7 +87,7 @@ int __hash_page_4K(unsigned long ea, unsigned long access, unsigned long vsid,
 	subpg_pte = new_pte & ~subpg_prot;
 	rflags = htab_convert_pte_flags(subpg_pte);
 
-	if (!cpu_has_feature(CPU_FTR_NOEXECUTE) &&
+	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
 	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE)) {
 
 		/*
@@ -258,7 +258,7 @@ int __hash_page_64K(unsigned long ea, unsigned long access,
 
 	rflags = htab_convert_pte_flags(new_pte);
 
-	if (!cpu_has_feature(CPU_FTR_NOEXECUTE) &&
+	if (cpu_has_feature(CPU_FTR_NOEXECUTE) &&
 	    !cpu_has_feature(CPU_FTR_COHERENT_ICACHE))
 		rflags = hash_page_do_lazy_icache(rflags, __pte(old_pte), trap);