From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by lists.proxmox.com (Postfix) with ESMTPS id BA39671C92 for ; Fri, 20 May 2022 10:43:27 +0200 (CEST) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id B09BD18581 for ; Fri, 20 May 2022 10:43:27 +0200 (CEST) Received: from proxmox-new.maurer-it.com (proxmox-new.maurer-it.com [94.136.29.106]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by firstgate.proxmox.com (Proxmox) with ESMTPS id 5C9EC1856B for ; Fri, 20 May 2022 10:43:26 +0200 (CEST) Received: from proxmox-new.maurer-it.com (localhost.localdomain [127.0.0.1]) by proxmox-new.maurer-it.com (Proxmox) with ESMTP id 10F0C420CC for ; Fri, 20 May 2022 10:43:26 +0200 (CEST) From: Dominik Csapak To: pve-devel@lists.proxmox.com Date: Fri, 20 May 2022 10:43:25 +0200 Message-Id: <20220520084325.1388661-2-d.csapak@proxmox.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220520084325.1388661-1-d.csapak@proxmox.com> References: <20220520084325.1388661-1-d.csapak@proxmox.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-SPAM-LEVEL: Spam detection results: 0 AWL 0.116 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record T_SCC_BODY_TEXT_LINE -0.01 - Subject: [pve-devel] [PATCH docs 2/2] pcie-passthrough: add short note about iommu passthrough mode X-BeenThere: pve-devel@lists.proxmox.com X-Mailman-Version: 2.1.29 Precedence: list List-Id: Proxmox VE development discussion List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 20 May 2022 08:43:27 -0000 that explains in one sentence what it does, that it can increase performance and how to activate it. Signed-off-by: Dominik Csapak --- 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