e0561e60f1
The ARM virt machines put firmware in flash memory. To configure it,
you use -drive if=pflash,unit=0,... and optionally -drive
if=pflash,unit=1,...
Why two -drive? This permits setting up one part of the flash memory
read-only, and the other part read/write. It also makes upgrading
firmware on the host easier. Below the hood, we get two separate
flash devices, because we were too lazy to improve our flash device
models to support sector protection.
The problem at hand is to do the same with -blockdev somehow, as one
more step towards deprecating -drive.
We recently solved this problem for x86 PC machines, in commit
ebc29e1beab. See the commit message for design rationale.
This commit solves it for ARM virt basically the same way: new machine
properties pflash0, pflash1 forward to the onboard flash devices'
properties. Requires creating the onboard devices in the
.instance_init() method virt_instance_init(). The existing code to
pick up drives defined with -drive if=pflash is replaced by code to
desugar into the machine properties.
There are a few behavioral differences, though:
* The flash devices are always present (x86: only present if
configured)
* Flash base addresses and sizes are fixed (x86: sizes depend on
images, mapped back to back below a fixed address)
* -bios configures contents of first pflash (x86: -bios configures ROM
contents)
* -bios is rejected when first pflash is also configured with -machine
pflash0=... (x86: bios is silently ignored then)
* -machine pflash1=... does not require -machine pflash0=... (x86: it
does).
The actual code is a bit simpler than for x86 mostly due to the first
two differences.
Before the patch, all the action is in create_flash(), called from the
machine's .init() method machvirt_init():
main()
machine_run_board_init()
machvirt_init()
create_flash()
create_one_flash() for flash[0]
create
configure
includes obeying -drive if=pflash,unit=0
realize
map
fall back to -bios
create_one_flash() for flash[1]
create
configure
includes obeying -drive if=pflash,unit=1
realize
map
update FDT
To make the machine properties work, we need to move device creation
to its .instance_init() method virt_instance_init().
Another complication is machvirt_init()'s computation of
@firmware_loaded: it predicts what create_flash() will do. Instead of
predicting what create_flash()'s replacement virt_firmware_init() will
do, I decided to have virt_firmware_init() return what it did.
Requires calling it a bit earlier.
Resulting call tree:
main()
current_machine = object_new()
...
virt_instance_init()
virt_flash_create()
virt_flash_create1() for flash[0]
create
configure: set defaults
become child of machine [NEW]
add machine prop pflash0 as alias for drive [NEW]
virt_flash_create1() for flash[1]
create
configure: set defaults
become child of machine [NEW]
add machine prop pflash1 as alias for drive [NEW]
for all machine props from the command line: machine_set_property()
...
property_set_alias() for machine props pflash0, pflash1
...
set_drive() for cfi.pflash01 prop drive
this is how -machine pflash0=... etc set
machine_run_board_init(current_machine);
virt_firmware_init()
pflash_cfi01_legacy_drive()
legacy -drive if=pflash,unit=0 and =1 [NEW]
virt_flash_map()
virt_flash_map1() for flash[0]
configure: num-blocks
realize
map
virt_flash_map1() for flash[1]
configure: num-blocks
realize
map
fall back to -bios
virt_flash_fdt()
update FDT
You have László to thank for making me explain this in detail.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Acked-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 20190416091348.26075-4-armbru@redhat.com
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
QEMU README
===========
QEMU is a generic and open source machine & userspace emulator and
virtualizer.
QEMU is capable of emulating a complete machine in software without any
need for hardware virtualization support. By using dynamic translation,
it achieves very good performance. QEMU can also integrate with the Xen
and KVM hypervisors to provide emulated hardware while allowing the
hypervisor to manage the CPU. With hypervisor support, QEMU can achieve
near native performance for CPUs. When QEMU emulates CPUs directly it is
capable of running operating systems made for one machine (e.g. an ARMv7
board) on a different machine (e.g. an x86_64 PC board).
QEMU is also capable of providing userspace API virtualization for Linux
and BSD kernel interfaces. This allows binaries compiled against one
architecture ABI (e.g. the Linux PPC64 ABI) to be run on a host using a
different architecture ABI (e.g. the Linux x86_64 ABI). This does not
involve any hardware emulation, simply CPU and syscall emulation.
QEMU aims to fit into a variety of use cases. It can be invoked directly
by users wishing to have full control over its behaviour and settings.
It also aims to facilitate integration into higher level management
layers, by providing a stable command line interface and monitor API.
It is commonly invoked indirectly via the libvirt library when using
open source applications such as oVirt, OpenStack and virt-manager.
QEMU as a whole is released under the GNU General Public License,
version 2. For full licensing details, consult the LICENSE file.
Building
========
QEMU is multi-platform software intended to be buildable on all modern
Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
of other UNIX targets. The simple steps to build QEMU are:
mkdir build
cd build
../configure
make
Additional information can also be found online via the QEMU website:
https://qemu.org/Hosts/Linux
https://qemu.org/Hosts/Mac
https://qemu.org/Hosts/W32
Submitting patches
==================
The QEMU source code is maintained under the GIT version control system.
git clone https://git.qemu.org/git/qemu.git
When submitting patches, one common approach is to use 'git
format-patch' and/or 'git send-email' to format & send the mail to the
qemu-devel@nongnu.org mailing list. All patches submitted must contain
a 'Signed-off-by' line from the author. Patches should follow the
guidelines set out in the HACKING and CODING_STYLE files.
Additional information on submitting patches can be found online via
the QEMU website
https://qemu.org/Contribute/SubmitAPatch
https://qemu.org/Contribute/TrivialPatches
The QEMU website is also maintained under source control.
git clone https://git.qemu.org/git/qemu-web.git
https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/
A 'git-publish' utility was created to make above process less
cumbersome, and is highly recommended for making regular contributions,
or even just for sending consecutive patch series revisions. It also
requires a working 'git send-email' setup, and by default doesn't
automate everything, so you may want to go through the above steps
manually for once.
For installation instructions, please go to
https://github.com/stefanha/git-publish
The workflow with 'git-publish' is:
$ git checkout master -b my-feature
$ # work on new commits, add your 'Signed-off-by' lines to each
$ git publish
Your patch series will be sent and tagged as my-feature-v1 if you need to refer
back to it in the future.
Sending v2:
$ git checkout my-feature # same topic branch
$ # making changes to the commits (using 'git rebase', for example)
$ git publish
Your patch series will be sent with 'v2' tag in the subject and the git tip
will be tagged as my-feature-v2.
Bug reporting
=============
The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
found when running code built from QEMU git or upstream released sources
should be reported via:
https://bugs.launchpad.net/qemu/
If using QEMU via an operating system vendor pre-built binary package, it
is preferable to report bugs to the vendor's own bug tracker first. If
the bug is also known to affect latest upstream code, it can also be
reported via launchpad.
For additional information on bug reporting consult:
https://qemu.org/Contribute/ReportABug
Contact
=======
The QEMU community can be contacted in a number of ways, with the two
main methods being email and IRC
- qemu-devel@nongnu.org
https://lists.nongnu.org/mailman/listinfo/qemu-devel
- #qemu on irc.oftc.net
Information on additional methods of contacting the community can be
found online via the QEMU website:
https://qemu.org/Contribute/StartHere
-- End