drivers/vfio_pci_core: Change PXD_ORDER check from switch case to if/else block

[ Upstream commit 948b71a ]

Architectures like PowerPC uses runtime defined values for
PMD_ORDER/PUD_ORDER. This is because it can use either RADIX or HASH MMU
at runtime using kernel cmdline. So the pXd_index_size is not known at
compile time. Without this fix, when we add huge pfn support on powerpc
in the next patch, vfio_pci_core driver compilation can fail with the
following errors.

  CC [M]  drivers/vfio/vfio_main.o
  CC [M]  drivers/vfio/group.o
  CC [M]  drivers/vfio/container.o
  CC [M]  drivers/vfio/virqfd.o
  CC [M]  drivers/vfio/vfio_iommu_spapr_tce.o
  CC [M]  drivers/vfio/pci/vfio_pci_core.o
  CC [M]  drivers/vfio/pci/vfio_pci_intrs.o
  CC [M]  drivers/vfio/pci/vfio_pci_rdwr.o
  CC [M]  drivers/vfio/pci/vfio_pci_config.o
  CC [M]  drivers/vfio/pci/vfio_pci.o
  AR      kernel/built-in.a
../drivers/vfio/pci/vfio_pci_core.c: In function ‘vfio_pci_vmf_insert_pfn’:
../drivers/vfio/pci/vfio_pci_core.c:1678:9: error: case label does not reduce to an integer constant
 1678 |         case PMD_ORDER:
      |         ^~~~
../drivers/vfio/pci/vfio_pci_core.c:1682:9: error: case label does not reduce to an integer constant
 1682 |         case PUD_ORDER:
      |         ^~~~
make[6]: *** [../scripts/Makefile.build:289: drivers/vfio/pci/vfio_pci_core.o] Error 1
make[6]: *** Waiting for unfinished jobs....
make[5]: *** [../scripts/Makefile.build:546: drivers/vfio/pci] Error 2
make[5]: *** Waiting for unfinished jobs....
make[4]: *** [../scripts/Makefile.build:546: drivers/vfio] Error 2
make[3]: *** [../scripts/Makefile.build:546: drivers] Error 2

Fixes: f9e54c3 ("vfio/pci: implement huge_fault support")
Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>
Reviewed-by: Alex Williamson <alex@shazbot.org>
Reviewed-by: Christophe Leroy (CS GROUP) <chleroy@kernel.org>
Signed-off-by: Madhavan Srinivasan <maddy@linux.ibm.com>
Link: https://patch.msgid.link/b155e19993ee1f5584c72050192eb468b31c5029.1773058761.git.ritesh.list@gmail.com
Signed-off-by: Sasha Levin <sashal@kernel.org>

Author: riteshharjani

drivers/vfio/pci/vfio_pci_core.c

@@ -1687,21 +1687,16 @@ vm_fault_t vfio_pci_vmf_insert_pfn(struct vfio_pci_core_device *vdev,
 	if (vdev->pm_runtime_engaged || !__vfio_pci_memory_enabled(vdev))
 		return VM_FAULT_SIGBUS;
 
-	switch (order) {
-	case 0:
+	if (!order)
 		return vmf_insert_pfn(vmf->vma, vmf->address, pfn);
-#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
-	case PMD_ORDER:
+
+	if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_PFNMAP) && order == PMD_ORDER)
 		return vmf_insert_pfn_pmd(vmf, pfn, false);
-#endif
-#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
-	case PUD_ORDER:
+
+	if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_PUD_PFNMAP) && order == PUD_ORDER)
 		return vmf_insert_pfn_pud(vmf, pfn, false);
-		break;
-#endif
-	default:
-		return VM_FAULT_FALLBACK;
-	}
+
+	return VM_FAULT_FALLBACK;
 }
 EXPORT_SYMBOL_GPL(vfio_pci_vmf_insert_pfn);