mirror of
https://github.com/xen-project/xen.git
synced 2026-10-28 02:01:24 +01:00
Daniel Kiper
c5b9805bc1
There is a problem with place_string() which is used as early memory
allocator. It gets memory chunks starting from start symbol and goes
down. Sadly this does not work when Xen is loaded using multiboot2
protocol because then the start lives on 1 MiB address and we should
not allocate a memory from below of it. So, I tried to use mem_lower
address calculated by GRUB2. However, this solution works only on some
machines. There are machines in the wild (e.g. Dell PowerEdge R820)
which uses first ~640 KiB for boot services code or data... :-(((
Hence, we need new memory allocator for Xen EFI boot code which is
quite simple and generic and could be used by place_string() and
efi_arch_allocate_mmap_buffer(). I think about following solutions:
1) We could use native EFI allocation functions (e.g. AllocatePool()
or AllocatePages()) to get memory chunk. However, later (somewhere
in __start_xen()) we must copy its contents to safe place or reserve
it in e820 memory map and map it in Xen virtual address space. This
means that the code referring to Xen command line, loaded modules and
EFI memory map, mostly in __start_xen(), will be further complicated
and diverge from legacy BIOS cases. Additionally, both former things
have to be placed below 4 GiB because their addresses are stored in
multiboot_info_t structure which has 32-bit relevant members.
2) We may allocate memory area statically somewhere in Xen code which
could be used as memory pool for early dynamic allocations. Looks
quite simple. Additionally, it would not depend on EFI at all and
could be used on legacy BIOS platforms if we need it. However, we
must carefully choose size of this pool. We do not want increase Xen
binary size too much and waste too much memory but also we must fit
at least memory map on x86 EFI platforms. As I saw on small machine,
e.g. IBM System x3550 M2 with 8 GiB RAM, memory map may contain more
than 200 entries. Every entry on x86-64 platform is 40 bytes in size.
So, it means that we need more than 8 KiB for EFI memory map only.
Additionally, if we use this memory pool for Xen and modules command
line storage (it would be used when xen.efi is executed as EFI application)
then we should add, I think, about 1 KiB. In this case, to be on safe
side, we should assume at least 64 KiB pool for early memory allocations.
Which is about 4 times of our earlier calculations. However, during
discussion on Xen-devel Jan Beulich suggested that just in case we should
use 1 MiB memory pool like it is in original place_string() implementation.
So, let's use 1 MiB as it was proposed. If we think that we should not
waste unallocated memory in the pool on running system then we can mark
this region as __initdata and move all required data to dynamically
allocated places somewhere in __start_xen().
2a) We could put memory pool into .bss.page_aligned section. Then allocate
memory chunks starting from the lowest address. After init phase we can
free unused portion of the memory pool as in case of .init.text or .init.data
sections. This way we do not need to allocate any space in image file and
freeing of unused area in the memory pool is very simple.
Now #2a solution is implemented because it is quite simple and requires
limited number of changes, especially in __start_xen().
New allocator is quite generic and can be used on ARM platforms too.
Though it is not enabled on ARM yet due to lack of some prereq.
List of them is placed before ebmalloc code.
Signed-off-by: Daniel Kiper <daniel.kiper@oracle.com>
Acked-by: Jan Beulich <jbeulich@suse.com>
Acked-by: Julien Grall <julien.grall@arm.com>
Reviewed-by: Doug Goldstein <cardoe@cardoe.com>
Tested-by: Doug Goldstein <cardoe@cardoe.com>
#################################
__ __ _ _ ___ _ _ _
\ \/ /___ _ __ | || | / _ \ _ _ _ __ ___| |_ __ _| |__ | | ___
\ // _ \ '_ \ | || || (_) |_____| | | | '_ \/ __| __/ _` | '_ \| |/ _ \
/ \ __/ | | | |__ _\__, |_____| |_| | | | \__ \ || (_| | |_) | | __/
/_/\_\___|_| |_| |_|(_)/_/ \__,_|_| |_|___/\__\__,_|_.__/|_|\___|
#################################
http://www.xen.org/
What is Xen?
============
Xen is a Virtual Machine Monitor (VMM) originally developed by the
Systems Research Group of the University of Cambridge Computer
Laboratory, as part of the UK-EPSRC funded XenoServers project. Xen
is freely-distributable Open Source software, released under the GNU
GPL. Since its initial public release, Xen has grown a large
development community, spearheaded by xen.org (http://www.xen.org).
This file contains some quick-start instructions to install Xen on
your system. For more information see http:/www.xen.org/ and
http://wiki.xen.org/
Quick-Start Guide
=================
First, this is just a quick-start guide. For more comprehensive
information see the INSTALL file and the Xen wiki at
http://wiki.xenproject.org and in particular
http://wiki.xenproject.org/wiki/Getting_Started.
Second, there are a number of prerequisites for building a Xen source
release. Make sure you have all the following installed, either by
visiting the project webpage or installing a pre-built package
provided by your OS distributor:
* GNU Make v3.80 or later
* C compiler and linker:
- For x86:
- GCC 4.1.2_20070115 or later
- GNU Binutils 2.16.91.0.5 or later
or
- Clang/LLVM 3.5 or later
- For ARM:
- GCC 4.8 or later
- GNU Binutils 2.24 or later
* Development install of zlib (e.g., zlib-dev)
* Development install of Python v2.3 or later (e.g., python-dev)
* Development install of curses (e.g., libncurses-dev)
* Development install of openssl (e.g., openssl-dev)
* Development install of x11 (e.g. xorg-x11-dev)
* Development install of uuid (e.g. uuid-dev)
* Development install of yajl (e.g. libyajl-dev)
* Development install of libaio (e.g. libaio-dev) version 0.3.107 or
greater.
* Development install of GLib v2.0 (e.g. libglib2.0-dev)
* Development install of Pixman (e.g. libpixman-1-dev)
* pkg-config
* bridge-utils package (/sbin/brctl)
* iproute package (/sbin/ip)
* GNU bison and GNU flex
* GNU gettext
* ACPI ASL compiler (iasl)
* Libc multiarch package (e.g. libc6-dev-i386 / glibc-devel.i686).
Required when building on a 64-bit platform to build
32-bit components which are enabled on a default build.
In addition to the above there are a number of optional build
prerequisites. Omitting these will cause the related features to be
disabled at compile time:
* Development install of Ocaml (e.g. ocaml-nox and
ocaml-findlib). Required to build ocaml components which
includes the alternative ocaml xenstored.
* cmake (if building vtpm stub domains)
* markdown
* figlet (for generating the traditional Xen start of day banner)
* systemd daemon development files
* Development install of libnl3 (e.g., libnl-3-200,
libnl-3-dev, etc). Required if network buffering is desired
when using Remus with libxl. See docs/README.remus for detailed
information.
* 16-bit x86 assembler, loader and compiler for qemu-traditional / rombios
(dev86 rpm or bin86 & bcc debs)
* Development install of liblzma for rombios
Second, you need to acquire a suitable kernel for use in domain 0. If
possible you should use a kernel provided by your OS distributor. If
no suitable kernel is available from your OS distributor then refer to
http://wiki.xen.org/wiki/XenDom0Kernels for suggestions for
suitable kernels to use.
If you are looking to compile a Dom0 kernel from source, please refer to
http://wiki.xen.org/wiki/XenParavirtOps.
[NB. Unless noted otherwise, all the following steps should be
performed with root privileges.]
1. Download and untar the source tarball file. This will be a
file named xen-unstable-src.tgz, or xen-$version-src.tgz.
You can also pull the current version from the git or mercurial
repositories at http://xenbits.xen.org/
# tar xzf xen-unstable-src.tgz
Assuming you are using the unstable tree, this will
untar into xen-unstable. The rest of the instructions
use the unstable tree as an example, substitute the
version for unstable.
2. cd to xen-unstable (or whatever you sensibly rename it to).
3. For the very first build, or if you want to destroy build trees,
perform the following steps:
# ./configure
# make world
# make install
See the documentation in the INSTALL file for more info.
This will create and install onto the local machine. It will build
the xen binary (xen.gz), the tools and the documentation.
You can override the destination for make install by setting DESTDIR
to some value.
4. To rebuild an existing tree without modifying the config:
# make dist
This will build and install xen, tools, and docs into the local dist/
directory.
You can override the destination for make install by setting DISTDIR
to some value.
make install and make dist differ in that make install does the
right things for your local machine (installing the appropriate
version of udev scripts, for example), but make dist includes all
versions of those scripts, so that you can copy the dist directory
to another machine and install from that distribution.
xenstore: xenstored and oxenstored
====================================
Xen uses a configuration database called xenstore [0] to maintain configuration
and status information shared between domains. A daemon is implemented as part
of xenstore to act as an interface for access to the database for dom0 and
guests. Two xenstored daemons are supported, one written in C which we refer
to as the xenstored (sometimes referred to as cxenstored), and another written
in Ocaml called oxenstored. Details for xenstore and the different
implementations can be found on the wiki's xenstore reference guide [1] and
the xenstored [2] page. You can choose which xenstore you want to enable as
default on a system through configure:
./configure --with-xenstored=xenstored
./configure --with-xenstored=oxenstored
By default oxenstored will be used if the ocaml development tools are found.
If you enable oxenstored the xenstored will still be built and installed,
the xenstored used can be changed through the configuration file:
/etc/sysconfig/xencommons
or
/etc/default/xencommons
You can change the preferred xenstored you want to use in the configuration
but since we cannot stop the daemon a reboot will be required to make the
change take effect.
[0] http://wiki.xen.org/wiki/XenStore
[1] http://wiki.xen.org/wiki/XenStoreReference
[2] http://wiki.xen.org/wiki/Xenstored
Python Runtime Libraries
========================
Various tools, such as pygrub, have the following runtime dependencies:
* Python 2.3 or later.
URL: http://www.python.org/
Debian: python
Intel(R) Trusted Execution Technology Support
=============================================
Intel's technology for safer computing, Intel(R) Trusted Execution Technology
(Intel(R) TXT), defines platform-level enhancements that provide the building
blocks for creating trusted platforms. For more information, see
http://www.intel.com/technology/security/.
Intel(R) TXT support is provided by the Trusted Boot (tboot) module in
conjunction with minimal logic in the Xen hypervisor.
Tboot is an open source, pre- kernel/VMM module that uses Intel(R) TXT to
perform a measured and verified launch of an OS kernel/VMM.
The Trusted Boot module is available from
http://sourceforge.net/projects/tboot. This project hosts the code in a
mercurial repo at http://tboot.sourceforge.net/hg/tboot.hg and contains
tarballs of the source. Instructions in the tboot README describe how
to modify grub.conf to use tboot to launch Xen.
There are optional targets as part of Xen's top-level makefile that will
download and build tboot: install-tboot, build-tboot, dist-tboot, clean-tboot.
These will download the latest tar file from the SourceForge site using wget,
then build/install/dist according to Xen's settings.