On 04/30/2018 10:25 AM, Scott Rifenbark wrote:
Hi Martin,
See
https://yoctoproject.org/docs/2.5/dev-manual/dev-manual.html#qemu-kvm-cpu-compatibility
and let me know if this section works. I took your patch and did some
rewriting.
Thanks,
Scott
I like your changes; thanks!
On Fri, Apr 27, 2018 at 10:46 AM, Martin Kelly <mke...@xevo.com
<mailto:mke...@xevo.com>> wrote:
As suggested in a recent mail thread by Martin Jansa, there are cases in
which QEMU under KVM will crash because of CPU feature incompatibilities
between compiled binaries and the host CPU under which qemu is run.
Although this is hard to fully escape, we should document the issue to
help people work around it.
Signed-off-by: Martin Kelly <mke...@xevo.com <mailto:mke...@xevo.com>>
---
documentation/dev-manual/dev-manual-qemu.xml | 22
++++++++++++++++++++++
1 file changed, 22 insertions(+)
diff --git a/documentation/dev-manual/dev-manual-qemu.xml
b/documentation/dev-manual/dev-manual-qemu.xml
index f4719ebc3..1870a6a8d 100644
--- a/documentation/dev-manual/dev-manual-qemu.xml
+++ b/documentation/dev-manual/dev-manual-qemu.xml
@@ -343,6 +343,28 @@
</para>
</section>
+ <section id='qemu-kvm-cpu-compatibility'>
+ <title>QEMU CPU Compatiblity under KVM</title>
+
+ <para>
+ By default, the QEMU build compiles for and targets
core2duo (for
+ 64-bit x86) and pentium2 (for 32-bit x86). These CPUS
are chose to
+ have a broad range of CPU feature compatibility with
many commonly
+ used CPUs, but in some cases, they still support a CPU
feature that
+ your host CPU does not. Although this is not a problem
when QEMU
+ uses software emulation of the feature, it can be when
running with
+ KVM enabled. Specifically, software compiled with a
certain CPU
+ feature will crash when run on a CPU under KVM that
does not support
+ that feature. If this becomes a problem, you can
override QEMU's
+ runtime CPU setting by changing the
<filename>QB_CPU_KVM</filename>
+ variable in <filename>qemuboot.conf</filename> in the
image deploy
+ directory. This setting specifies a
<filename>-cpu</filename> option
+ passed into QEMU in the <filename>runqemu</filename>
script. Running
+ <filename>qemu -cpu help</filename> will give a list of
supported
+ CPU types available.
+ </para>
+ </section>
+
<section id='qemu-dev-performance'>
<title>QEMU Performance</title>
--
2.11.0
--
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