Re: [RFC v1 1/2] drivers/vfio_pci_core: Change PXD_ORDER check from switch case to if/else block
From: "Christophe Leroy (CS GROUP)" <chleroy@kernel.org>
Date: 2026-02-27 06:42:12
Also in:
kvm, linux-mm
Le 27/02/2026 à 07:16, Ritesh Harjani (IBM) a écrit :
quoted hunk ↗ jump to hunk
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: f9e54c3a2f5b7 ("vfio/pci: implement huge_fault support") Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com> --- drivers/vfio/pci/vfio_pci_core.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-)diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index d43745fe4c84..5395a6f30904 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c@@ -1670,21 +1670,20 @@ 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 == 0) { return vmf_insert_pfn(vmf->vma, vmf->address, pfn); + }
Those braces are unneeded as all legs of the if/else are single lines
#ifdef CONFIG_ARCH_SUPPORTS_PMD_PFNMAP
ifdef could be replaced by IS_ENABLED() because PxD_ORDER and vmf_insert_pfn_xxx() are declared all the time
- case PMD_ORDER:
+ else if (order == PMD_ORDER) {'else' is not needed because every 'if' leads to a return statement
return vmf_insert_pfn_pmd(vmf, pfn, false);
+ }
#endif
#ifdef CONFIG_ARCH_SUPPORTS_PUD_PFNMAP
- case PUD_ORDER:
+ else if (order == PUD_ORDER) {
return vmf_insert_pfn_pud(vmf, pfn, false);
- break;
+ }
#endif
- default:
- return VM_FAULT_FALLBACK;
- }
+ return VM_FAULT_FALLBACK;So at the end we should get something like: if (!order) return vmf_insert_pfn(vmf->vma, vmf->address, pfn); if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_PMD_PFNMAP) && order == PMD_ORDER) return vmf_insert_pfn_pmd(vmf, pfn, false); if (IS_ENABLED(CONFIG_ARCH_SUPPORTS_PUD_PFNMAP) && order == PMD_ORDER) return vmf_insert_pfn_pud(vmf, pfn, false); return VM_FAULT_FALLBACK;
} EXPORT_SYMBOL_GPL(vfio_pci_vmf_insert_pfn); -- 2.53.0