From: Dominik Csapak <d.csapak@proxmox.com>
To: pve-devel@lists.proxmox.com
Subject: [pve-devel] [PATCH docs 2/2] pcie-passthrough: add short note about iommu passthrough mode
Date: Fri, 20 May 2022 10:43:25 +0200 [thread overview]
Message-ID: <20220520084325.1388661-2-d.csapak@proxmox.com> (raw)
In-Reply-To: <20220520084325.1388661-1-d.csapak@proxmox.com>
that explains in one sentence what it does, that it can increase
performance and how to activate it.
Signed-off-by: Dominik Csapak <d.csapak@proxmox.com>
---
qm-pci-passthrough.adoc | 18 ++++++++++++++++++
1 file changed, 18 insertions(+)
diff --git a/qm-pci-passthrough.adoc b/qm-pci-passthrough.adoc
index 5ef325d..28bb4fc 100644
--- a/qm-pci-passthrough.adoc
+++ b/qm-pci-passthrough.adoc
@@ -62,6 +62,24 @@ The command line parameters are:
----
* for AMD CPUs it should be enabled automatically.
+
+If your hardware supports it, enabling IOMMU passthrough mode might increase
+performance, because then the VMs bypass the (default) DMA translation
+which is normally done by the hypervisor, before handing DMA requests off to
+the hardware IOMMU. You can enable it with adding
+
+----
+ iommu.passthrough=1
+----
+
+or
+
+----
+ iommu=pt
+----
+
+to the kernel commandline.
+
.Kernel Modules
You have to make sure the following modules are loaded. This can be achieved by
--
2.30.2
next prev parent reply other threads:[~2022-05-20 8:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-05-20 8:43 [pve-devel] [PATCH docs 1/2] pcie-passthrough: note that iommu activation is not always necessary Dominik Csapak
2022-05-20 8:43 ` Dominik Csapak [this message]
2022-11-18 10:17 ` [pve-devel] applied: " Thomas Lamprecht
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