mirror of
https://github.com/torvalds/linux.git
synced 2024-11-28 23:21:31 +00:00
c619a804cc
Add documentation on the following aspects of ACRN: 1) A brief introduction on the architecture of ACRN. 2) I/O request handling in ACRN. 3) CPUID functions of ACRN. To learn more about ACRN, please go to ACRN project website https://projectacrn.org, or the documentation page https://projectacrn.github.io/. Cc: Dave Hansen <dave.hansen@intel.com> Cc: Sen Christopherson <sean.j.christopherson@intel.com> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Fengwei Yin <fengwei.yin@intel.com> Cc: Zhi Wang <zhi.a.wang@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: Yu Wang <yu1.wang@intel.com> Cc: Reinette Chatre <reinette.chatre@intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Randy Dunlap <rdunlap@infradead.org> Reviewed-by: Zhi Wang <zhi.a.wang@intel.com> Reviewed-by: Reinette Chatre <reinette.chatre@intel.com> Reviewed-by: Borislav Petkov <bp@suse.de> Signed-off-by: Shuo Liu <shuo.a.liu@intel.com> Link: https://lore.kernel.org/r/20210207031040.49576-2-shuo.a.liu@intel.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
98 lines
4.4 KiB
ReStructuredText
98 lines
4.4 KiB
ReStructuredText
.. 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.
|