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25c9780d38
This fixes a nasty regression in qemu-4.1 for the 'pseries' machine, caused by the new "dual" interrupt controller model. Specifically, qemu can crash when used with KVM if a 'system_reset' is requested while there's active I/O in the guest. The problem is that in spapr_machine_reset() we: 1. Reset the CAS vector state spapr_ovec_cleanup(spapr->ov5_cas); 2. Reset all devices qemu_devices_reset() 3. Reset the irq subsystem spapr_irq_reset(); However (1) implicitly changes the interrupt delivery mode, because whether we're using XICS or XIVE depends on the CAS state. We don't properly initialize the new irq mode until (3) though - in particular setting up the KVM devices. During (2), we can temporarily drop the BQL allowing some irqs to be delivered which will go to an irq system that's not properly set up. Specifically, if the previous guest was in (KVM) XIVE mode, the CAS reset will put us back in XICS mode. kvm_kernel_irqchip() still returns true, because XIVE was using KVM, however XICs doesn't have its KVM components intialized and kernel_xics_fd == -1. When the irq is delivered it goes via ics_kvm_set_irq() which assert()s that kernel_xics_fd != -1. This change addresses the problem by delaying the CAS reset until after the devices reset. The device reset should quiesce all the devices so we won't get irqs delivered while we mess around with the IRQ. The CAS reset and irq re-initialize should also now be under the same BQL critical section so nothing else should be able to interrupt it either. We also move the spapr_irq_msi_reset() used in one of the legacy irq modes, since it logically makes sense at the same point as the spapr_irq_reset() (it's essentially an equivalent operation for older machine types). Since we don't need to switch between different interrupt controllers for those old machine types it shouldn't actually be broken in those cases though. Cc: Cédric Le Goater <clg@kaod.org> Fixes: |
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| Changelog | ||
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| configure | ||
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| HACKING | ||
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| Kconfig.host | ||
| LICENSE | ||
| MAINTAINERS | ||
| Makefile | ||
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| README | ||
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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