mirror of https://github.com/xemu-project/xemu.git
72194664c8
Since the introduction of VSMT in 2.11, the spacing of VCPU ids
between cores is controllable through a machine property instead
of being only dictated by the SMT mode of the host:
cpu->vcpu_id = (cc->core_id * spapr->vsmt / smp_threads) + i
Until recently, the machine code would try to change the SMT mode
of the host to be equal to VSMT or exit. This allowed the rest of
the code to assume that kvmppc_smt_threads() == spapr->vsmt is
always true.
Recent commit "8904e5a75005 spapr: Adjust default VSMT value for
better migration compatibility" relaxed the rule. If the VSMT
mode cannot be set in KVM for some reasons, but the requested
CPU topology is compatible with the current SMT mode, then we
let the guest run with kvmppc_smt_threads() != spapr->vsmt.
This breaks quite a few places in the code, in particular when
calculating DRC indexes.
This is what happens on a POWER host with subcores-per-core=2 (ie,
supports up to SMT4) when passing the following topology:
-smp threads=4,maxcpus=16 \
-device host-spapr-cpu-core,core-id=4,id=core1 \
-device host-spapr-cpu-core,core-id=8,id=core2
qemu-system-ppc64: warning: Failed to set KVM's VSMT mode to 8 (errno -22)
This is expected since KVM is limited to SMT4, but the guest is started
anyway because this topology can run on SMT4 even with a VSMT8 spacing.
But when we look at the DT, things get nastier:
cpus {
...
ibm,drc-indexes = <0x4 0x10000000 0x10000004 0x10000008 0x1000000c>;
This means that we have the following association:
CPU core device | DRC | VCPU id
-----------------+------------+---------
boot core | 0x10000000 | 0
core1 | 0x10000004 | 4
core2 | 0x10000008 | 8
core3 | 0x1000000c | 12
But since the spacing of VCPU ids is 8, the DRC for core1 points to a
VCPU that doesn't exist, the DRC for core2 points to the first VCPU of
core1 and and so on...
...
PowerPC,POWER8@0 {
...
ibm,my-drc-index = <0x10000000>;
...
};
PowerPC,POWER8@8 {
...
ibm,my-drc-index = <0x10000008>;
...
};
PowerPC,POWER8@10 {
...
No ibm,my-drc-index property for this core since 0x10000010 doesn't
exist in ibm,drc-indexes above.
...
};
};
...
interrupt-controller {
...
ibm,interrupt-server-ranges = <0x0 0x10>;
With a spacing of 8, the highest VCPU id for the given topology should be:
16 * 8 / 4 = 32 and not 16
...
linux,phandle = <0x7e7323b8>;
interrupt-controller;
};
And CPU hot-plug/unplug is broken:
(qemu) device_del core1
pseries-hotplug-cpu: Cannot find CPU (drc index 10000004) to remove
(qemu) device_del core2
cpu 4 (hwid 8) Ready to die...
cpu 5 (hwid 9) Ready to die...
cpu 6 (hwid 10) Ready to die...
cpu 7 (hwid 11) Ready to die...
These are the VCPU ids of core1 actually
(qemu) device_add host-spapr-cpu-core,core-id=12,id=core3
(qemu) device_del core3
pseries-hotplug-cpu: Cannot find CPU (drc index 1000000c) to remove
This patches all the code in hw/ppc/spapr.c to assume the VSMT
spacing when manipulating VCPU ids.
Fixes:
|
||
|---|---|---|
| accel | ||
| audio | ||
| backends | ||
| block | ||
| bsd-user | ||
| capstone@22ead3e0bf | ||
| chardev | ||
| contrib | ||
| crypto | ||
| default-configs | ||
| disas | ||
| docs | ||
| dtc@e54388015a | ||
| fpu | ||
| fsdev | ||
| gdb-xml | ||
| hw | ||
| include | ||
| io | ||
| libdecnumber | ||
| linux-headers | ||
| linux-user | ||
| migration | ||
| nbd | ||
| net | ||
| pc-bios | ||
| po | ||
| qapi | ||
| qga | ||
| qobject | ||
| qom | ||
| replay | ||
| roms | ||
| scripts | ||
| scsi | ||
| slirp | ||
| stubs | ||
| target | ||
| tcg | ||
| tests | ||
| trace | ||
| ui | ||
| util | ||
| .dir-locals.el | ||
| .editorconfig | ||
| .exrc | ||
| .gdbinit | ||
| .gitignore | ||
| .gitmodules | ||
| .mailmap | ||
| .shippable.yml | ||
| .travis.yml | ||
| CODING_STYLE | ||
| COPYING | ||
| COPYING.LIB | ||
| COPYING.PYTHON | ||
| Changelog | ||
| HACKING | ||
| LICENSE | ||
| MAINTAINERS | ||
| Makefile | ||
| Makefile.objs | ||
| Makefile.target | ||
| README | ||
| VERSION | ||
| arch_init.c | ||
| balloon.c | ||
| block.c | ||
| blockdev-nbd.c | ||
| blockdev.c | ||
| blockjob.c | ||
| bootdevice.c | ||
| bt-host.c | ||
| bt-vhci.c | ||
| configure | ||
| cpus-common.c | ||
| cpus.c | ||
| device-hotplug.c | ||
| device_tree.c | ||
| disas.c | ||
| dma-helpers.c | ||
| dump.c | ||
| exec.c | ||
| gdbstub.c | ||
| hmp-commands-info.hx | ||
| hmp-commands.hx | ||
| hmp.c | ||
| hmp.h | ||
| ioport.c | ||
| iothread.c | ||
| memory.c | ||
| memory_ldst.inc.c | ||
| memory_mapping.c | ||
| module-common.c | ||
| monitor.c | ||
| numa.c | ||
| os-posix.c | ||
| os-win32.c | ||
| qapi-schema.json | ||
| qdev-monitor.c | ||
| qdict-test-data.txt | ||
| qemu-bridge-helper.c | ||
| qemu-doc.texi | ||
| qemu-ga.texi | ||
| qemu-img-cmds.hx | ||
| qemu-img.c | ||
| qemu-img.texi | ||
| qemu-io-cmds.c | ||
| qemu-io.c | ||
| qemu-keymap.c | ||
| qemu-nbd.c | ||
| qemu-nbd.texi | ||
| qemu-option-trace.texi | ||
| qemu-options-wrapper.h | ||
| qemu-options.h | ||
| qemu-options.hx | ||
| qemu-seccomp.c | ||
| qemu-tech.texi | ||
| qemu.nsi | ||
| qemu.sasl | ||
| qmp.c | ||
| qtest.c | ||
| replication.c | ||
| replication.h | ||
| rules.mak | ||
| thunk.c | ||
| tpm.c | ||
| trace-events | ||
| version.rc | ||
| vl.c | ||
README
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 git://git.qemu.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
https://qemu.org/Contribute/SubmitAPatch
https://qemu.org/Contribute/TrivialPatches
The QEMU website is also maintained under source control.
git clone git://git.qemu.org/qemu-web.git
https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/
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