linux-kernel - [PATCH v2 15/22] Documentation: userspace-api: iommufd: Update vCMDQ

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Message-ID: <820dfdee121292fe4cf891feb86f82ceea521e22.1745646960.git.nicolinc@nvidia.com>
Date: Fri, 25 Apr 2025 22:58:10 -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>,
	<shuah@...nel.org>, <jsnitsel@...hat.com>, <nathan@...nel.org>,
	<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>,
	<linux-kselftest@...r.kernel.org>, <patches@...ts.linux.dev>,
	<mochs@...dia.com>, <alok.a.tiwari@...cle.com>, <vasant.hegde@....com>
Subject: [PATCH v2 15/22] Documentation: userspace-api: iommufd: Update vCMDQ

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 | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/Documentation/userspace-api/iommufd.rst b/Documentation/userspace-api/iommufd.rst
index b0df15865dec..afca749652ee 100644
--- a/Documentation/userspace-api/iommufd.rst
+++ b/Documentation/userspace-api/iommufd.rst
@@ -124,6 +124,19 @@ 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_VCMDQ, representing a hardware queue as a subset of a vIOMMU's
+  virtualization feature for a VM to directly execute guest-issued commands to
+  invalidate HW cache entries holding the mappings or translations of a guest-
+  owned stage-1 page table. Along with this queue object, iommufd provides the
+  user space an mmap interface for VMM to mmap a physical MMIO region from the
+  host physical address space to a guest physical address space, to exclusively
+  control the allocated vCMDQ HW. Thus, when allocating a vCMDQ, the VMM must
+  request a pair of VMA info (vm_pgoff/size) for a later mmap call. The length
+  argument of an mmap call could be smaller than the given size for a paritial
+  mmap, but the given vm_pgoff (as the addr argument of the mmap call) should
+  never be offsetted, which also implies that the 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 +283,7 @@ 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_vcmdq for IOMMUFD_OBJ_VCMDQ.
 
 Several terminologies when looking at these datastructures:
 
-- 
2.43.0