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Message-ID: <0beddeaaa4a8a7a45ce93ff21c543ae58be64908.1746139811.git.nicolinc@nvidia.com>
Date: Thu, 1 May 2025 16:01:22 -0700
From: Nicolin Chen <nicolinc@...dia.com>
To: <jgg@...dia.com>, <kevin.tian@...el.com>, <corbet@....net>,
<will@...nel.org>
CC: <bagasdotme@...il.com>, <robin.murphy@....com>, <joro@...tes.org>,
<thierry.reding@...il.com>, <vdumpa@...dia.com>, <jonathanh@...dia.com>,
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<peterz@...radead.org>, <yi.l.liu@...el.com>, <mshavit@...gle.com>,
<praan@...gle.com>, <zhangzekun11@...wei.com>, <iommu@...ts.linux.dev>,
<linux-doc@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>, <linux-tegra@...r.kernel.org>,
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Subject: [PATCH v3 16/23] Documentation: userspace-api: iommufd: Update vQUEUE
With the introduction of the new object and its infrastructure, update the
doc to reflect that.
Signed-off-by: Nicolin Chen <nicolinc@...dia.com>
---
Documentation/userspace-api/iommufd.rst | 15 +++++++++++++++
1 file changed, 15 insertions(+)
diff --git a/Documentation/userspace-api/iommufd.rst b/Documentation/userspace-api/iommufd.rst
index b0df15865dec..ed32713a97a3 100644
--- a/Documentation/userspace-api/iommufd.rst
+++ b/Documentation/userspace-api/iommufd.rst
@@ -124,6 +124,20 @@ Following IOMMUFD objects are exposed to userspace:
used to allocate a vEVENTQ. Each vIOMMU can support multiple types of vEVENTS,
but is confined to one vEVENTQ per vEVENTQ type.
+- IOMMUFD_OBJ_VQUEUE, representing a hardware accelerated virtual queue, as a
+ subset of IOMMU's virtualization features, for the IOMMU HW to directly read
+ or write the virtual queue memory owned by a guest OS. This HW-acceleration
+ allows VM to work with the IOMMU HW directly without a VM Exit, i.e. reducing
+ overhead from the hypercalls. Along with this vQUEUE object, iommufd provides
+ user space an mmap interface for VMM to mmap a physical MMIO region from the
+ host physical address space to the guest physical address space, allowing the
+ guest OS to control the allocated vQUEUE HW. Thus, when allocating a vQUEUE,
+ the VMM must request a pair of VMA info (vm_pgoff/size) for an mmap syscall.
+ The length argument of an mmap syscall can be smaller than the given size for
+ a partial mmap, but the addr argument of the mmap syscall should never offset
+ from the returned vm_pgoff, which implies that an mmap will always start from
+ the beginning of the physical MMIO region.
+
All user-visible objects are destroyed via the IOMMU_DESTROY uAPI.
The diagrams below show relationships between user-visible objects and kernel
@@ -270,6 +284,7 @@ User visible objects are backed by following datastructures:
- iommufd_viommu for IOMMUFD_OBJ_VIOMMU.
- iommufd_vdevice for IOMMUFD_OBJ_VDEVICE.
- iommufd_veventq for IOMMUFD_OBJ_VEVENTQ.
+- iommufd_vqueue for IOMMUFD_OBJ_VQUEUE.
Several terminologies when looking at these datastructures:
--
2.43.0
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