diff options
Diffstat (limited to 'drivers/vfio')
| -rw-r--r-- | drivers/vfio/pci/vfio_pci_core.c | 19 |
1 files changed, 18 insertions, 1 deletions
diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 1cbc990d42e0..df6f99bdf70d 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -1862,8 +1862,25 @@ int vfio_pci_core_mmap(struct vfio_device *core_vdev, struct vm_area_struct *vma /* * See remap_pfn_range(), called from vfio_pci_fault() but we can't * change vm_flags within the fault handler. Set them now. + * + * VM_ALLOW_ANY_UNCACHED: The VMA flag is implemented for ARM64, + * allowing KVM stage 2 device mapping attributes to use Normal-NC + * rather than DEVICE_nGnRE, which allows guest mappings + * supporting write-combining attributes (WC). ARM does not + * architecturally guarantee this is safe, and indeed some MMIO + * regions like the GICv2 VCPU interface can trigger uncontained + * faults if Normal-NC is used. + * + * To safely use VFIO in KVM the platform must guarantee full + * safety in the guest where no action taken against a MMIO + * mapping can trigger an uncontained failure. The assumption is + * that most VFIO PCI platforms support this for both mapping types, + * at least in common flows, based on some expectations of how + * PCI IP is integrated. Hence VM_ALLOW_ANY_UNCACHED is set in + * the VMA flags. */ - vm_flags_set(vma, VM_IO | VM_PFNMAP | VM_DONTEXPAND | VM_DONTDUMP); + vm_flags_set(vma, VM_ALLOW_ANY_UNCACHED | VM_IO | VM_PFNMAP | + VM_DONTEXPAND | VM_DONTDUMP); vma->vm_ops = &vfio_pci_mmap_ops; return 0; |