attrs: update cephdocs template to quincy

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

diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc
index 5ef325d38140d1f1863aa6a9a22bbccff291fae8..df6cf214c54f04fbfb870098ba7d77c85d63b6d3 100644 (file)
--- a/qm-pci-passthrough.adoc
+++ b/qm-pci-passthrough.adoc
@@ -42,25 +42,35 @@ Configuration
 Once you ensured that your hardware supports passthrough, you will need to do
 some configuration to enable PCI(e) passthrough.
 
-
 .IOMMU
 
-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 might need to be activated on the
-xref:sysboot_edit_kernel_cmdline[kernel commandline].
-(On newer kernels, this should not be necessary.)
+First, you have to enable IOMMU support in your BIOS/UEFI. Usually the
+corresponding setting is called `IOMMU` or `VT-d`,but you should find the exact
+option name in the manual of your motherboard.
 
-The command line parameters are:
+For Intel CPUs, you may also need to enable the IOMMU on the
+xref:sysboot_edit_kernel_cmdline[kernel command line] for older (pre-5.15)
+kernels by adding:
 
-* for Intel CPUs:
-+
 ----
  intel_iommu=on
 ----
-* for AMD CPUs it should be enabled automatically.
+
+For AMD CPUs it should be enabled automatically.
+
+.IOMMU Passthrough Mode
+
+If your hardware supports IOMMU passthrough mode, enabling this mode might
+increase performance.
+This is because VMs then bypass the (default) DMA translation normally
+performed by the hyper-visor and instead pass DMA requests directly to the
+hardware IOMMU. To enable these options, add:
+
+----
+ iommu=pt
+----
+
+to the xref:sysboot_edit_kernel_cmdline[kernel commandline].
 
 .Kernel Modules