From: Ankit Agrawal <ankita@nvidia.com> mainline inclusion from mainline-v6.9-rc1 commit a39d3a966a090989b89c0287a67cd98c85ae2f52 category: bugfix bugzilla: https://atomgit.com/openeuler/kernel/issues/9340 CVE: NA Reference: https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?i... -------------------------------- The VM_ALLOW_ANY_UNCACHED 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 expectation 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. So make vfio-pci set the VM_ALLOW_ANY_UNCACHED flag. Suggested-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Jason Gunthorpe <jgg@nvidia.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Alex Williamson <alex.williamson@redhat.com> Reviewed-by: David Hildenbrand <david@redhat.com> Reviewed-by: Marc Zyngier <maz@kernel.org> Signed-off-by: Ankit Agrawal <ankita@nvidia.com> Signed-off-by: Tian Zheng <zhengtian10@huawei.com> --- drivers/vfio/pci/vfio_pci_core.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-) diff --git a/drivers/vfio/pci/vfio_pci_core.c b/drivers/vfio/pci/vfio_pci_core.c index 8dc9cef1f78c..529a3e113a3c 100644 --- a/drivers/vfio/pci/vfio_pci_core.c +++ b/drivers/vfio/pci/vfio_pci_core.c @@ -1892,8 +1892,25 @@ 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; -- 2.33.0