summaryrefslogtreecommitdiffstats
path: root/Documentation/virt/acrn
diff options
context:
space:
mode:
Diffstat (limited to 'Documentation/virt/acrn')
-rw-r--r--Documentation/virt/acrn/cpuid.rst46
-rw-r--r--Documentation/virt/acrn/index.rst12
-rw-r--r--Documentation/virt/acrn/introduction.rst43
-rw-r--r--Documentation/virt/acrn/io-request.rst97
4 files changed, 198 insertions, 0 deletions
diff --git a/Documentation/virt/acrn/cpuid.rst b/Documentation/virt/acrn/cpuid.rst
new file mode 100644
index 000000000000..65fa4b9c1798
--- /dev/null
+++ b/Documentation/virt/acrn/cpuid.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+ACRN CPUID bits
+===============
+
+A guest VM running on an ACRN hypervisor can check some of its features using
+CPUID.
+
+ACRN cpuid functions are:
+
+function: 0x40000000
+
+returns::
+
+ eax = 0x40000010
+ ebx = 0x4e524341
+ ecx = 0x4e524341
+ edx = 0x4e524341
+
+Note that this value in ebx, ecx and edx corresponds to the string
+"ACRNACRNACRN". The value in eax corresponds to the maximum cpuid function
+present in this leaf, and will be updated if more functions are added in the
+future.
+
+function: define ACRN_CPUID_FEATURES (0x40000001)
+
+returns::
+
+ ebx, ecx, edx
+ eax = an OR'ed group of (1 << flag)
+
+where ``flag`` is defined as below:
+
+================================= =========== ================================
+flag value meaning
+================================= =========== ================================
+ACRN_FEATURE_PRIVILEGED_VM 0 guest VM is a privileged VM
+================================= =========== ================================
+
+function: 0x40000010
+
+returns::
+
+ ebx, ecx, edx
+ eax = (Virtual) TSC frequency in kHz.
diff --git a/Documentation/virt/acrn/index.rst b/Documentation/virt/acrn/index.rst
new file mode 100644
index 000000000000..b5f793e73df5
--- /dev/null
+++ b/Documentation/virt/acrn/index.rst
@@ -0,0 +1,12 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===============
+ACRN Hypervisor
+===============
+
+.. toctree::
+ :maxdepth: 1
+
+ introduction
+ io-request
+ cpuid
diff --git a/Documentation/virt/acrn/introduction.rst b/Documentation/virt/acrn/introduction.rst
new file mode 100644
index 000000000000..f8d081bc084d
--- /dev/null
+++ b/Documentation/virt/acrn/introduction.rst
@@ -0,0 +1,43 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+ACRN Hypervisor Introduction
+============================
+
+The ACRN Hypervisor is a Type 1 hypervisor, running directly on bare-metal
+hardware. It has a privileged management VM, called Service VM, to manage User
+VMs and do I/O emulation.
+
+ACRN userspace is an application running in the Service VM that emulates
+devices for a User VM based on command line configurations. ACRN Hypervisor
+Service Module (HSM) is a kernel module in the Service VM which provides
+hypervisor services to the ACRN userspace.
+
+Below figure shows the architecture.
+
+::
+
+ Service VM User VM
+ +----------------------------+ | +------------------+
+ | +--------------+ | | | |
+ | |ACRN userspace| | | | |
+ | +--------------+ | | | |
+ |-----------------ioctl------| | | | ...
+ |kernel space +----------+ | | | |
+ | | HSM | | | | Drivers |
+ | +----------+ | | | |
+ +--------------------|-------+ | +------------------+
+ +---------------------hypercall----------------------------------------+
+ | ACRN Hypervisor |
+ +----------------------------------------------------------------------+
+ | Hardware |
+ +----------------------------------------------------------------------+
+
+ACRN userspace allocates memory for the User VM, configures and initializes the
+devices used by the User VM, loads the virtual bootloader, initializes the
+virtual CPU state and handles I/O request accesses from the User VM. It uses
+ioctls to communicate with the HSM. HSM implements hypervisor services by
+interacting with the ACRN Hypervisor via hypercalls. HSM exports a char device
+interface (/dev/acrn_hsm) to userspace.
+
+The ACRN hypervisor is open for contribution from anyone. The source repo is
+available at https://github.com/projectacrn/acrn-hypervisor.
diff --git a/Documentation/virt/acrn/io-request.rst b/Documentation/virt/acrn/io-request.rst
new file mode 100644
index 000000000000..6cc3ea0fa1f5
--- /dev/null
+++ b/Documentation/virt/acrn/io-request.rst
@@ -0,0 +1,97 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+I/O request handling
+====================
+
+An I/O request of a User VM, which is constructed by the hypervisor, is
+distributed by the ACRN Hypervisor Service Module to an I/O client
+corresponding to the address range of the I/O request. Details of I/O request
+handling are described in the following sections.
+
+1. I/O request
+--------------
+
+For each User VM, there is a shared 4-KByte memory region used for I/O requests
+communication between the hypervisor and Service VM. An I/O request is a
+256-byte structure buffer, which is 'struct acrn_io_request', that is filled by
+an I/O handler of the hypervisor when a trapped I/O access happens in a User
+VM. ACRN userspace in the Service VM first allocates a 4-KByte page and passes
+the GPA (Guest Physical Address) of the buffer to the hypervisor. The buffer is
+used as an array of 16 I/O request slots with each I/O request slot being 256
+bytes. This array is indexed by vCPU ID.
+
+2. I/O clients
+--------------
+
+An I/O client is responsible for handling User VM I/O requests whose accessed
+GPA falls in a certain range. Multiple I/O clients can be associated with each
+User VM. There is a special client associated with each User VM, called the
+default client, that handles all I/O requests that do not fit into the range of
+any other clients. The ACRN userspace acts as the default client for each User
+VM.
+
+Below illustration shows the relationship between I/O requests shared buffer,
+I/O requests and I/O clients.
+
+::
+
+ +------------------------------------------------------+
+ | Service VM |
+ |+--------------------------------------------------+ |
+ || +----------------------------------------+ | |
+ || | shared page ACRN userspace | | |
+ || | +-----------------+ +------------+ | | |
+ || +----+->| acrn_io_request |<-+ default | | | |
+ || | | | +-----------------+ | I/O client | | | |
+ || | | | | ... | +------------+ | | |
+ || | | | +-----------------+ | | |
+ || | +-|--------------------------------------+ | |
+ ||---|----|-----------------------------------------| |
+ || | | kernel | |
+ || | | +----------------------+ | |
+ || | | | +-------------+ HSM | | |
+ || | +--------------+ | | | |
+ || | | | I/O clients | | | |
+ || | | | | | | |
+ || | | +-------------+ | | |
+ || | +----------------------+ | |
+ |+---|----------------------------------------------+ |
+ +----|-------------------------------------------------+
+ |
+ +----|-------------------------------------------------+
+ | +-+-----------+ |
+ | | I/O handler | ACRN Hypervisor |
+ | +-------------+ |
+ +------------------------------------------------------+
+
+3. I/O request state transition
+-------------------------------
+
+The state transitions of an ACRN I/O request are as follows.
+
+::
+
+ FREE -> PENDING -> PROCESSING -> COMPLETE -> FREE -> ...
+
+- FREE: this I/O request slot is empty
+- PENDING: a valid I/O request is pending in this slot
+- PROCESSING: the I/O request is being processed
+- COMPLETE: the I/O request has been processed
+
+An I/O request in COMPLETE or FREE state is owned by the hypervisor. HSM and
+ACRN userspace are in charge of processing the others.
+
+4. Processing flow of I/O requests
+----------------------------------
+
+a. The I/O handler of the hypervisor will fill an I/O request with PENDING
+ state when a trapped I/O access happens in a User VM.
+b. The hypervisor makes an upcall, which is a notification interrupt, to
+ the Service VM.
+c. The upcall handler schedules a worker to dispatch I/O requests.
+d. The worker looks for the PENDING I/O requests, assigns them to different
+ registered clients based on the address of the I/O accesses, updates
+ their state to PROCESSING, and notifies the corresponding client to handle.
+e. The notified client handles the assigned I/O requests.
+f. The HSM updates I/O requests states to COMPLETE and notifies the hypervisor
+ of the completion via hypercalls.