At the moment the following QEMU command line triggers an assertion
failure (minimal reproducer by Cole):
qemu-system-aarch64 \
-machine virt-2.6,accel=tcg \
-nodefaults \
-no-user-config \
-nographic -monitor stdio \
-device virtio-scsi-device,id=scsi0 \
-device virtio-scsi-device,id=scsi1 \
-drive file=foo.img,format=raw,if=none,id=d0 \
-device scsi-hd,bus=scsi0.0,drive=d0 \
-drive file=foo.img,format=raw,if=none,id=d1 \
-device scsi-hd,bus=scsi1.0,drive=d1
qemu-system-aarch64: migration/savevm.c:615:
vmstate_register_with_alias_id:
Assertion `!se->compat || se->instance_id == 0' failed.
The reason is that the vmstate sections for the two scsi-hd devices are
not uniquely identifiable by name.
The direct parent buses of the scsi-hd devices -- scsi0.0 and scsi1.0 --
support the BusClass.get_dev_path member function. scsibus_get_dev_path()
formats a device path prefix with the help of its topologically parent
bus, and then appends the chan🆔lun triplet to it. For both scsi-hd
devices, this triplet is 0:0:0.
(Here we use "device path" in the QEMU migration sense, for vmstate
section identification, not in the OFW or UEFI device path senses.)
The virtio-scsi HBA is plugged into the virtio-mmio bus (implemented by
the internal VirtIOMMIOProxy device). This bus class
(TYPE_VIRTIO_MMIO_BUS) inherits, as its get_dev_path() member function,
the virtio_bus_get_dev_path() method from its parent class
(TYPE_VIRTIO_BUS).
virtio_bus_get_dev_path() does not format any kind of device address on
its own; "virtio addresses" are transport-specific. Therefore
virtio_bus_get_dev_path() asks the topologically parent bus of the proxy
object (implementing the specific virtio transport) to format the address
of the proxy object.
(For virtio-pci devices (where the proxy is an instance of VirtIOPCIProxy,
plugged into a PCI bus), this ends up in pcibus_get_dev_path().)
However, VirtIOMMIOProxy is usually (in practice: always) plugged into
"main-system-bus", the singleton TYPE_SYSTEM_BUS object. This BusClass
does not support formatting QEMU vmstate device paths at all (as
SysBusDevice objects can have zero or more IO ports and zero or more MMIO
regions). Hence the formatting request delegated from
virtio_bus_get_dev_path() gets answered with NULL.
The end result is that the two scsi-hd devices end up with the same device
path "0:0:0", which triggers the assert.
We can solve this by recognizing that virtio-mmio transports are
distinguished from each other by their base addresses in MMIO address
space. Implement virtio_mmio_bus_get_dev_path() as follows:
(1) The virtio device whose devpath is to be formatted resides on a
virtio-mmio bus that is implemented by a VirtIOMMIOProxy object. Ask
the parent bus of VirtIOMMIOProxy to format the device path of
VirtIOMMIOProxy, as a path prefix. (This is identical to what
virtio_bus_get_dev_path() does.)
(2) Append the base address of VirtIOMMIOProxy to the device path, such
as:
- virtio-mmio@000000000a003e00,
- virtio-mmio@000000000a003c00.
Given that these device paths are placed in the migration stream, step (2)
above, if done unconditionally, would break migration. So make that step
conditional on a new VirtIOMMIOProxy property, which is enabled for 2.7
machine types and later.
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Cole Robinson <crobinso@redhat.com>
Cc: Dr. David Alan Gilbert <dgilbert@redhat.com>
Cc: Kevin Zhao <kevin.zhao@linaro.org>
Cc: Peter Maydell <peter.maydell@linaro.org>
Cc: Tom Hanson <thomas.hanson@linaro.org>
Reported-by: Kevin Zhao <kevin.zhao@linaro.org>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-id: 1467739394-28357-1-git-send-email-lersek@redhat.com
Fixes: https://bugs.launchpad.net/qemu/+bug/1594239
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
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
Complete details of the process for building and configuring QEMU for
all supported host platforms can be found in the qemu-tech.html file.
Additional information can also be found online via the QEMU website:
http://qemu-project.org/Hosts/Linux
http://qemu-project.org/Hosts/W32
Submitting patches
==================
The QEMU source code is maintained under the GIT version control system.
git clone git://git.qemu-project.org/qemu.git
When submitting patches, the preferred 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
http://qemu-project.org/Contribute/SubmitAPatch
http://qemu-project.org/Contribute/TrivialPatches
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:
http://qemu-project.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
http://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:
http://qemu-project.org/Contribute/StartHere
-- End
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