pcie-passthrough: note that iommu activation is not always necessary

[pve-docs.git] / qm-pci-passthrough.adoc

diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc
index edaa01f5011945fdf8eb20d03a2469b6df2d9cf0..5ef325d38140d1f1863aa6a9a22bbccff291fae8 100644 (file)
--- a/qm-pci-passthrough.adoc
+++ b/qm-pci-passthrough.adoc
@@ -49,8 +49,9 @@ First, the IOMMU support has to be enabled in your BIOS/UEFI. Most often, that
 options is named `IOMMU` or `VT-d`, but check the manual for your motherboard
 for the exact option you need to enable.
 
-Then, the IOMMU has to be activated on the
+Then, the IOMMU might need to be activated on the
 xref:sysboot_edit_kernel_cmdline[kernel commandline].
+(On newer kernels, this should not be necessary.)
 
 The command line parameters are:
 
@@ -233,6 +234,24 @@ An example of PCIe passthrough with a GPU set to primary:
 # qm set VMID -hostpci0 02:00,pcie=on,x-vga=on
 ----
 
+.PCI ID overrides
+
+You can override the PCI vendor ID, device ID, and subsystem IDs that will be
+seen by the guest. This is useful if your device is a variant with an ID that
+your guest's drivers don't recognize, but you want to force those drivers to be
+loaded anyway (e.g. if you know your device shares the same chipset as a
+supported variant).
+
+The available options are `vendor-id`, `device-id`, `sub-vendor-id`, and
+`sub-device-id`. You can set any or all of these to override your device's
+default IDs.
+
+For example:
+
+----
+# qm set VMID -hostpci0 02:00,device-id=0x10f6,sub-vendor-id=0x0000
+----
+
 
 Other considerations
 ^^^^^^^^^^^^^^^^^^^^