path: root/Documentation
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authorAlex Williamson <>2012-01-12 12:39:54 +0200
committerGreg Kroah-Hartman <>2012-01-18 07:31:54 -0800
commitc4e7f9022e506c6635a5037713c37118e23193e4 (patch)
tree02f95483e4fb2d7f05bdca533c02cb3fc4ccc957 /Documentation
parent4fd9e326e5001982747225f0f7bb462e34ae9215 (diff)
KVM: Device assignment permission checks
(cherry picked from commit 3d27e23b17010c668db311140b17bbbb70c78fb9) Only allow KVM device assignment to attach to devices which: - Are not bridges - Have BAR resources (assume others are special devices) - The user has permissions to use Assigning a bridge is a configuration error, it's not supported, and typically doesn't result in the behavior the user is expecting anyway. Devices without BAR resources are typically chipset components that also don't have host drivers. We don't want users to hold such devices captive or cause system problems by fencing them off into an iommu domain. We determine "permission to use" by testing whether the user has access to the PCI sysfs resource files. By default a normal user will not have access to these files, so it provides a good indication that an administration agent has granted the user access to the device. [Yang Bai: add missing #include] [avi: fix comment style] Signed-off-by: Alex Williamson <> Signed-off-by: Yang Bai <> Signed-off-by: Marcelo Tosatti <> Signed-off-by: Greg Kroah-Hartman <>
Diffstat (limited to 'Documentation')
1 files changed, 4 insertions, 0 deletions
diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index 57c9336dfc7e..13ab8379b4eb 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -1134,6 +1134,10 @@ following flags are specified:
The KVM_DEV_ASSIGN_ENABLE_IOMMU flag is a mandatory option to ensure
isolation of the device. Usages not specifying this flag are deprecated.
+Only PCI header type 0 devices with PCI BAR resources are supported by
+device assignment. The user requesting this ioctl must have read/write
+access to the PCI sysfs resource files associated with the device.