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Besides the fact that we did not have that for the current supported boards, that makes sense for this new, virtualized mode, that is meant to be run on top of full-fledged x86 64 CPUs. By having xAPIC mode access only, Jailhouse has to intercept those MMIO reads and writes, in order to examine what they do and arbitrate if it's safe or not (e.g. not all values are accepted to ICR register). This means that we can't run away from having a VM-exit event for each and every access to APIC memory region and this impacts the latency the guest OS observes over bare metal a lot. When in x2APIC mode, Jailhouse does not require VM-exits for MSR accesses other that writes to the ICR register, so the latency the guest observes is reduced to almost zero. Here are some outputs of the the command line $ sudo ./tools/jailhouse cell stats tiny-demo on a Jailhouse's root cell console, for one of the Zephyr demos using LOAPIC timers, left for a couple of seconds: Statistics for tiny-demo cell (x2APIC root, x2APIC inmate) COUNTER SUM PER SEC vmexits_total 7 0 vmexits_management 3 0 vmexits_cr 2 0 vmexits_cpuid 1 0 vmexits_msr 1 0 vmexits_exception 0 0 vmexits_hypercall 0 0 vmexits_mmio 0 0 vmexits_pio 0 0 vmexits_xapic 0 0 vmexits_xsetbv 0 0 Statistics for tiny-demo cell (xAPIC root, xAPIC inmate) COUNTER SUM PER SEC vmexits_total 4087 40 vmexits_xapic 4080 40 vmexits_management 3 0 vmexits_cr 2 0 vmexits_cpuid 1 0 vmexits_msr 1 0 vmexits_exception 0 0 vmexits_hypercall 0 0 vmexits_mmio 0 0 vmexits_pio 0 0 vmexits_xsetbv 0 0 Statistics for tiny-demo cell (xAPIC root, x2APIC inmate) COUNTER SUM PER SEC vmexits_total 4087 40 vmexits_msr 4080 40 vmexits_management 3 0 vmexits_cr 2 0 vmexits_cpuid 1 0 vmexits_exception 0 0 vmexits_hypercall 0 0 vmexits_mmio 0 0 vmexits_pio 0 0 vmexits_xapic 0 0 vmexits_xsetbv 0 0 See that under x2APIC mode on both Jailhouse/root-cell and guest, the interruptions from the hypervisor are minimal. That is not the case when Jailhouse is on xAPIC mode, though. Note also that, as a plus, x2APIC accesses on the guest will map to xAPIC MMIO on the hypervisor just fine. Signed-off-by: Gustavo Lima Chaves <gustavo.lima.chaves@intel.com> |
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.known-issues | ||
arch | ||
boards | ||
doc | ||
drivers | ||
dts | ||
ext | ||
include | ||
kernel | ||
lib | ||
misc | ||
samples | ||
scripts | ||
subsys | ||
tests | ||
.checkpatch.conf | ||
.gitattributes | ||
.gitignore | ||
.gitlint | ||
.mailmap | ||
.shippable.yml | ||
CODEOWNERS | ||
CONTRIBUTING.rst | ||
Kbuild | ||
Kconfig | ||
Kconfig.zephyr | ||
LICENSE | ||
Makefile | ||
Makefile.inc | ||
Makefile.test | ||
README.rst | ||
zephyr-env.sh |
Zephyr Project ############## .. raw:: html <a href="https://bestpractices.coreinfrastructure.org/projects/74"><img src="https://bestpractices.coreinfrastructure.org/projects/74/badge"></a> <img src="https://api.shippable.com/projects/58ffb2b8baa5e307002e1d79/badge?branch=master"> The Zephyr Project is a scalable real-time operating system (RTOS) supporting multiple hardware architectures, optimized for resource constrained devices, and built with security in mind. The Zephyr OS is based on a small-footprint kernel designed for use on resource-constrained systems: from simple embedded environmental sensors and LED wearables to sophisticated smart watches and IoT wireless gateways. The Zephyr kernel supports multiple architectures, including ARM Cortex-M, Intel x86, ARC, NIOS II, Tensilica Xtensa, and RISC V, and a large number of `supported boards`_. .. below included in doc/introduction/introduction.rst .. start_include_here Community Support ***************** The Zephyr Project Developer Community includes developers from member organizations and the general community all joining in the development of software within the Zephyr Project. Members contribute and discuss ideas, submit bugs and bug fixes, and provide training. They also help those in need through the community's forums such as mailing lists and IRC channels. Anyone can join the developer community and the community is always willing to help its members and the User Community to get the most out of the Zephyr Project. Welcome to the Zephyr community! Resources ********* Here's a quick summary of resources to find your way around the Zephyr Project support systems: * **Zephyr Project Website**: The https://zephyrproject.org website is the central source of information about the Zephyr Project. On this site, you'll find background and current information about the project as well as all the relevant links to project material. For a quick start, refer to the `Zephyr Introduction`_ and `Getting Started Guide`_. * **Releases**: Source code for Zephyr kernel releases are available at https://zephyrproject.org/developers/#downloads. On this page, you'll find release information, and links to download or clone source code from our GitHub repository. You'll also find links for the Zephyr SDK, a moderated collection of tools and libraries used to develop your applications. * **Source Code in GitHub**: Zephyr Project source code is maintained on a public GitHub repository at https://github.com/zephyrproject-rtos/zephyr. You'll find information about getting access to the repository and how to contribute to the project in this `Contribution Guide`_ document. * **Samples Code**: In addition to the kernel source code, there are also many documented `Sample and Demo Code Examples`_ that can help show you how to use Zephyr services and subsystems. * **Documentation**: Extensive Project technical documentation is developed along with the Zephyr kernel itself, and can be found at https://zephyrproject.org/doc. Additional documentation is maintained in the `Zephyr GitHub wiki`_. * **Issue Reporting and Tracking**: Requirements and Issue tracking is done in the Github issues system: https://github.com/zephyrproject-rtos/zephyr/issues. You can browse through the reported issues and submit issues of your own. * **Security-related Issue Reporting and Tracking**: For security-related inquiries or reporting suspected security-related bugs in the Zephyr OS, please send email to vulnerabilities@zephyrproject.org. We will assess and fix flaws according to our security policy outlined in the Zephyr Project `Security Overview`_. Security related issue tracking is done in JIRA. The location of this JIRA is https://zephyrprojectsec.atlassian.net. * **Mailing List**: The `Zephyr Mailing Lists`_ are perhaps the most convenient way to track developer discussions and to ask your own support questions to the Zephyr project community. You can also read through message archives to follow past posts and discussions, a good thing to do to discover more about the Zephyr project. * **IRC Chatting**: You can chat online with the Zephyr project developer community and other users in our IRC channel #zephyrproject on the freenode.net IRC server. You can use the http://webchat.freenode.net web client or use a client-side application such as pidgin. .. _supported boards: https://www.zephyrproject.org/doc/boards/boards.html .. _Zephyr Introduction: https://www.zephyrproject.org/doc/introduction/introducing_zephyr.html .. _Getting Started Guide: https://www.zephyrproject.org/doc/getting_started/getting_started.html .. _Contribution Guide: https://www.zephyrproject.org/doc/contribute/contribute_guidelines.html .. _Zephyr GitHub wiki: https://github.com/zephyrproject-rtos/zephyr/wiki .. _Zephyr Mailing Lists: https://lists.zephyrproject.org/ .. _Sample and Demo Code Examples: https://www.zephyrproject.org/doc/samples/samples.html .. _Security Overview: https://www.zephyrproject.org/doc/security/security-overview.html