powerpc fixes for 6.3 #3

- Fix false detection of read faults, introduced by execute-only support.
 
  - Fix a build failure when GENERIC_ALLOCATOR is not selected.
 
 Thanks to: Russell Currey, Randy Dunlap, Michal Suchánek, Nathan Lynch,
 Benjamin Gray.
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Merge tag 'powerpc-6.3-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:

 - Fix false detection of read faults, introduced by execute-only
   support

 - Fix a build failure when GENERIC_ALLOCATOR is not selected

Thanks to Russell Currey, Randy Dunlap, Michal Suchánek, Nathan Lynch,
and Benjamin Gray.

* tag 'powerpc-6.3-3' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/mm: Fix false detection of read faults
  powerpc/pseries: RTAS work area requires GENERIC_ALLOCATOR

arch/powerpc/mm/fault.c

@@ -271,11 +271,16 @@ static bool access_error(bool is_write, bool is_exec, struct vm_area_struct *vma
 	}
 
 	/*
-	 * Check for a read fault.  This could be caused by a read on an
-	 * inaccessible page (i.e. PROT_NONE), or a Radix MMU execute-only page.
+	 * VM_READ, VM_WRITE and VM_EXEC all imply read permissions, as
+	 * defined in protection_map[].  Read faults can only be caused by
+	 * a PROT_NONE mapping, or with a PROT_EXEC-only mapping on Radix.
 	 */
-	if (unlikely(!(vma->vm_flags & VM_READ)))
+	if (unlikely(!vma_is_accessible(vma)))
 		return true;
+
+	if (unlikely(radix_enabled() && ((vma->vm_flags & VM_ACCESS_FLAGS) == VM_EXEC)))
+		return true;
+
 	/*
 	 * We should ideally do the vma pkey access check here. But in the
 	 * fault path, handle_mm_fault() also does the same check. To avoid

arch/powerpc/platforms/pseries/Kconfig

@@ -7,6 +7,7 @@ config PPC_PSERIES
 	select OF_DYNAMIC
 	select FORCE_PCI
 	select PCI_MSI
+	select GENERIC_ALLOCATOR
 	select PPC_XICS
 	select PPC_XIVE_SPAPR
 	select PPC_ICP_NATIVE