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From: Nicolin Chen <nicolinc@nvidia.com>
To: <will@kernel.org>, <robin.murphy@arm.com>, <joro@8bytes.org>,
	<alex.williamson@redhat.com>, <cohuck@redhat.com>,
	<corbet@lwn.net>
Cc: <nicoleotsuka@gmail.com>, <vdumpa@nvidia.com>,
	<thierry.reding@gmail.com>, <linux-tegra@vger.kernel.org>,
	<nwatterson@nvidia.com>, <Jonathan.Cameron@huawei.com>,
	<jean-philippe@linaro.org>, <song.bao.hua@hisilicon.com>,
	<eric.auger@redhat.com>, <thunder.leizhen@huawei.com>,
	<yuzenghui@huawei.com>, <linux-kernel@vger.kernel.org>,
	<linux-arm-kernel@lists.infradead.org>,
	<iommu@lists.linux-foundation.org>, <kvm@vger.kernel.org>,
	<linux-doc@vger.kernel.org>
Subject: [RFC][PATCH v2 03/13] vfio: Document VMID control for IOMMU Virtualization
Date: Mon, 30 Aug 2021 19:59:13 -0700	[thread overview]
Message-ID: <20210831025923.15812-4-nicolinc@nvidia.com> (raw)
In-Reply-To: <20210831025923.15812-1-nicolinc@nvidia.com>

The VFIO API was enhanced to support VMID control with two
new iotcls to set and get VMID between the kernel and the
virtual machine hypervisor. So updating the document.

Signed-off-by: Nicolin Chen <nicolinc@nvidia.com>
---
 Documentation/driver-api/vfio.rst | 34 +++++++++++++++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/Documentation/driver-api/vfio.rst b/Documentation/driver-api/vfio.rst
index c663b6f97825..a76a17065cdd 100644
--- a/Documentation/driver-api/vfio.rst
+++ b/Documentation/driver-api/vfio.rst
@@ -239,6 +239,40 @@ group and can access them as follows::
 	/* Gratuitous device reset and go... */
 	ioctl(device, VFIO_DEVICE_RESET);
 
+IOMMU Virtual Machine Identifier (VMID)
+------------------------
+In case of virtualization, each VM is assigned a Virtual Machine Identifier
+(VMID). This VMID is used to tag translation lookaside buffer (TLB) entries,
+to identify which VM each entry belongs to. This tagging allows translations
+for multiple different VMs to be present in the TLBs at the same time.
+
+The IOMMU Kernel driver is responsible for allocating a VMID. However, only
+a hypervisor knows what physical devices get assigned to the same VM. Thus,
+when the first physical device gets assigned to the VM, once the hypervisor
+finishes its IOCTL call of VFIO_SET_IOMMU, it should call the following:
+
+struct vm {
+	int iommu_type;
+	uint32_t vmid;	/* initial value is VFIO_IOMMU_VMID_INVALID */
+} vm0;
+
+	/* ... */
+	ioctl(container->fd, VFIO_SET_IOMMU, vm0->iommu_type);
+	/* ... */
+	if (vm0->vmid == VFIO_IOMMU_VMID_INVALID)
+		ioctl(container->fd, VFIO_IOMMU_GET_VMID, &vm0->vmid);
+
+This VMID would be the shared value, across the entire VM, between all the
+physical devices that are assigned to it. So, when other physical devices
+get assigned to the VM, before the hypervisor runs into the IOCTL call of
+VFIO_IOMMU_SET_VMID, it should call the following:
+
+	/* ... */
+	ioctl(container->fd, VFIO_SET_IOMMU, vm0->iommu_type);
+	/* ... */
+	if (vm0->vmid != VFIO_IOMMU_VMID_INVALID)
+		ioctl(container->fd, VFIO_IOMMU_SET_VMID, vmid);
+
 VFIO User API
 -------------------------------------------------------------------------------
 
-- 
2.17.1


  parent reply	other threads:[~2021-08-31  3:07 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-31  2:59 [RFC][PATCH v2 00/13] iommu/arm-smmu-v3: Add NVIDIA implementation Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 01/13] iommu: Add set_nesting_vmid/get_nesting_vmid functions Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 02/13] vfio: add VFIO_IOMMU_GET_VMID and VFIO_IOMMU_SET_VMID Nicolin Chen
2021-08-31  2:59 ` Nicolin Chen [this message]
2021-08-31  2:59 ` [RFC][PATCH v2 04/13] vfio: add set_vmid and get_vmid for vfio_iommu_type1 Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 05/13] vfio/type1: Implement set_vmid and get_vmid Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 06/13] vfio/type1: Set/get VMID to/from iommu driver Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 07/13] iommu/arm-smmu-v3: Add shared VMID support for NESTING Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 08/13] iommu/arm-smmu-v3: Add VMID alloc/free helpers Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 09/13] iommu/arm-smmu-v3: Pass dev pointer to arm_smmu_detach_dev Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 10/13] iommu/arm-smmu-v3: Pass cmdq pointer in arm_smmu_cmdq_issue_cmdlist() Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 11/13] iommu/arm-smmu-v3: Add implementation infrastructure Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 12/13] iommu/arm-smmu-v3: Add support for NVIDIA CMDQ-Virtualization hw Nicolin Chen
2021-08-31  2:59 ` [RFC][PATCH v2 13/13] iommu/nvidia-smmu-v3: Add mdev interface support Nicolin Chen
2021-08-31 16:15 ` [RFC][PATCH v2 00/13] iommu/arm-smmu-v3: Add NVIDIA implementation Alex Williamson
2021-09-01  6:55   ` Tian, Kevin
2021-09-02 14:45     ` Jason Gunthorpe
2021-09-02 22:27       ` Tian, Kevin
2021-09-16 18:21         ` Nicolin Chen

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