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Release notes
=============
1. Preface
a. Proprietary notice
Copyright (c) 2012, ARM Limited
All rights reserved.
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED
WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER
OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING
IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF
THE POSSIBILITY OF SUCH DAMAGE.
b. License details
Copyright (c) 2009-2012, ARM Limited. All rights
reserved.
Redistribution and use in source and binary forms, with
or without modification, are permitted provided that the
following conditions are met:
* Redistributions of source code must retain the above
copyright notice,
this list of conditions and the following disclaimer.
* Redistributions in binary form must reproduce the
above copyright notice,
this list of conditions and the following disclaimer
in the documentation and/or other materials provided
with the distribution.
* Neither the name of ARM nor the names of its
contributors may be used to endorse or promote products
derived from this software without specific prior written
permission.
c. Document confidentiality status
Redistribution of source and compiled code is subject to the
license terms above.
d. Product status
ARM Virtualizer for Cortex-A15/Cortex-A7 Task Migration v2.3
e. Web address
Not applicable.
f. Feedback on the ARM Virtualizer software
None at present.
g. Feedback on this release note document
None at present.
2. Release details
a. Product release status
v2.3
b. ARM Virtualizer software release v2.3
This software release is a v2.3 snapshot of the ARM
Virtualizer software.
The ARM Virtualizer software is example code that demonstrates
cluster context switching capability on a coherent dual
cluster system composed of a Cortex-A7 cluster and a
Cortex-A15 cluster.
The intent behind this delivery is to allow
inspection of the software architecture and to
demonstrate existing functionality.
It is possible to execute the ARM Virtualizer software on a
Real-Time System Model (RTSM_VE_Cortex_A15x1_A7x1 and
RTSM_VE_Cortex_A15x4_A7x4).
This model may be obtained from ARM by separate arrangement.
c. Deliverables
This release contains the following file:
1. arm-virtualizer-v2_3-130312.tar.bz2
- Contains source code for a basic boot wrapper.
This boot wrapper performs minimal system initialization
and boots the system with the Virtualizer code. It also
permits booting the system with an optional Linux kernel
image and an accompanying root filesystem [both NOT
supplied with this release].
- Contains source code for the ARM Virtualizer software.
- Contains pertinent documentation covering the
release components, their installation and usage.
d. Functionality included
This release of the ARM Virtualizer software is capable of rapid
and robust cluster context switching on a coherent system
between a cluster of up to four Cortex-A7 processors and a
cluster of up to four Cortex-A15 processors.
In addition, this release of the ARM Virtualizer software
permits payload software (bare-metal software or a Linux
operating system kernel) built for the Cortex-A15 processor
cluster to run un-modified on a Cortex-A7 processor cluster.
This release does not support execution of software built for the
Cortex-A7 cluster on the Cortex-A15 cluster.
e. New features
1. It is possible to hotplug a cpu using the mechanisms provided
by the Linux 3.x cpu hotplug implementation. Please refer to
"docs/07-Linux-cpu-hotplug-howto.txt" for details regarding
how the Virtualizer software and Linux should be configured
to support cpu hotplug.
2. Context of the registers specified by the v7.1 Debug architecture
is saved and restored during a cluster context switch operation.
3. Use of inter-processor interrupts for HYP mode communication has
been made generic. It is possible to use an IPI for a particular
type of HYP mode operation. Requesting a cluster switch and
completing a virtual irq migration operation are the two types of
HYP mode operations that are currently supported.
f. Known issues
1. This release does not support execution of software
built for the Cortex-A7 cluster on the Cortex-A15
cluster.
2. This release is intended to be built in a Linux development
environment. Environments other than Linux are not supported.
3. The cache level chosen through a write to the CSSELR on the
Cortex-A7 cluster is not migrated to the Cortex-A15 cluster during
a subsequent migration.
4. Differences in the characteristics of the I-Cache between the
Cortex-A7 and Cortex-A15 are not hidden through the use of
Virtualization extensions by the Virtualizer.
5. Save & Restore of Debug context is done only when the memory mapped
interface is supported. Doing the same using the cp14 interface is
currently not supported.
6. Save & Restore of Debug context is still being tested.
7. Bug fix to support migration of virtual interrupts is still being
tested. [Please see 'v2.2 to v2.3' in Section g.]
8. Support for cpu hotplug is still being subject to
stress tests.
g. Issues resolved since last release
1. Bug fixes
v2.1:
1. vGIC HYP view interface handling code in (common/vgiclib.c) now
detects the number of implemented list registers from the vgic
type register instead of assuming that the maximum (64) will be
present.
v2.1 to v2.2:
1. Issue an DCCISW and not a DCCSW when DCCSIW was trapped in
trap_cp15_mrc_mcr_handle (big-little/virtualisor/virt_handle.c).
A DCCISW (Data Cache clean and invalidate by set/way) operation
was being incorrectly implemented as a DCCSW
(Data Cache clean by set/way)
operation by the Virtualizer.
2. Calculate l2_desc correctly in CreateL3PageTable
(big-little/common/pagetable_setup.c) for level
equals 2.
Correct index into Level-2 page table of the 2nd Stage
translations is being calculated when CreateL3PageTable() is
called to add a L3 page table for IPAs > 1GB.
3. Create second 4KB 2nd stage mapping for VGIC in
Create2ndStagePageTables
(big-little/common/pagetable_setup.c).
Mapping added to 2nd stage translation tables to cover the 2nd
4K memory map of the physical cpu interface of the vGIC (cpu
interface base + 0x1000).
4. Fix race condition during enabling CCI coherency in warm_reset
(big-little/secure_world/monmode_vectors.s).
A race condition existed while enabling CCI
coherency after a warm reset in the Secure world
code. This could have led to a case where
cpus1-3 start restoring the saved context
without taking part in CCI based coherency for a
brief period of time.
v2.2 to v2.3:
1. When a physical interrupt is migrated from one cpu interface to
another on any cluster, it is possible that its virtual interrupt
is in a pending state in the HYP view interface list registers.
It is now ensured that the virtual interrupt is also migrated by
requesting it to be added to the queue of virtual interrupts on
the destination cpu interface.
h. Test cases and results
In accordance with the delivery’s status as example code, testing is
sufficient to prove robustness of the basic implementation but does
not provide full coverage for all use cases.
1. This release has been tested for correct cluster switching
operation at ~12 million cycle switching intervals with
bare-metal and Linux kernel payloads.
2. This release has been tested using a select subset of an ARM
internal Linux based stress testing suite.
3. The Linux Test Project (LTP) cpu hotplug tests have
been run while cluster switching was performed
simultaneously. All tests passed.
i. Other information
Not applicable.
3. Documentation
The docs subdirectory contains the following notes:
01-Usage.txt: General installation and usage instructions.
02-Code-layout.txt: Overview of the code layout.
03-Linux-kernel-build.txt: Instructions on obtaining and
building a Linux kernel image suitable for the virtualizer.
04-Cache-hit-rate-howto.txt: Description of the MTI trace
plugin infrastructure and ways to use the trace for
estimating snoop hit rates across cluster switches.
05-FAQ.txt: Placeholder for commonly asked questions with
answers.
06-Optional-rootfs-build.txt: Instructions for building and
using rootfilesystems with the virtualizer.
07-Linux-cpu-hotplug-howto.txt: Instructions & guidelines to
use Linux CPU hotplug.
4. Tools
a. Tools
1. ARM Development Studio 5 - Version 5.8.
2. Real-Time System Model v7.0.1 (RTSM_VE_Cortex_A15x1_A7x1
and RTSM_VE_Cortex_A15x4_A7x4).
b. Operating systems
1. Ubuntu 10.10.
2. Red Hat Enterprise Linux WS release 4 (Nahant Update 4).
5. Support
ARM provides this software release purely as example software and
absolves itself of any support burden. ARM is open to receiving any
constructive feedback and at it's discretion, will endeavour to
incorporate any feedback in subsequent releases of this example
software.
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