Re: [PATCH v2 1/2] drivers/vfio_pci_core: Change PXD_ORDER check from switch case to if/else block

[Venkat <venkat88@linux.ibm.com>]

> On 9 Mar 2026, at 6:08 PM, Ritesh Harjani (IBM) <ritesh.list@gmail.com> wrote:
> 
> 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>
> ---

Tested-by: Venkat Rao Bagalkote <venkat88@linux.ibm.com>

Tested this patch, and with this, build is successful and reported issue is fixed.


WithOut this patch:

drivers/vfio/pci/vfio_pci_core.c: In function ‘vfio_pci_vmf_insert_pfn’:
drivers/vfio/pci/vfio_pci_core.c:1677:9: error: case label does not reduce to an integer constant
 1677 |         case PMD_ORDER:
      |         ^~~~
drivers/vfio/pci/vfio_pci_core.c:1681:9: error: case label does not reduce to an integer constant
 1681 |         case PUD_ORDER:
      |         ^~~~

Regards,
Venkat.
> v1 -> v2:
> 1. addressed review comments from Christophe [1]
> [1]: https://lore.kernel.org/linuxppc-dev/0b8fce7a61561640634317a5e287cdb4794715fd.1772170860.git.ritesh.list@gmail.com/
> 
> drivers/vfio/pci/vfio_pci_core.c | 19 +++++++------------
> 1 file changed, 7 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c
> index d43745fe4c84..0967307235b8 100644
> --- a/drivers/vfio/pci/vfio_pci_core.c
> +++ b/drivers/vfio/pci/vfio_pci_core.c
> @@ -1670,21 +1670,16 @@ 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);
> 
> --
> 2.39.5
> 
>