On 04/24/2017 09:31 AM, Richard Purdie wrote:
On Fri, 2017-04-21 at 17:21 -0700, Martin Kelly wrote:
Currently, the qemu CPUs for are specified as generic, but the built
artifacts are not. For example, we build x86-64 artifacts targeting
core2duo but run them in qemu with generic qemu/kvm CPUs. This causes
some packages that take advantage of the host architecture to crash
because they try to use CPU features not advertised by qemu. As an
example, Qt uses ssse3. When artifacts linked against Qt and built
targeting core2duo attempt to run on a generic qemu/kvm CPU, we get
the following crash:
Incompatible processor. This Qt build requires the following
features:
ssse3
We could fix this by making packages like Qt not take advantage of
CPU
features. However, we will probably keep facing similar issues over
time, so it's better to resolve them in a more enduring way.
Fix this by making the qemu -cpu arguments match the built artifacts.
Signed-off-by: Martin Kelly <[email protected]>
---
meta/conf/machine/include/qemuboot-x86.inc | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/meta/conf/machine/include/qemuboot-x86.inc
b/meta/conf/machine/include/qemuboot-x86.inc
index 06ac983..acd03a1 100644
--- a/meta/conf/machine/include/qemuboot-x86.inc
+++ b/meta/conf/machine/include/qemuboot-x86.inc
@@ -1,12 +1,12 @@
# For runqemu
IMAGE_CLASSES += "qemuboot"
QB_SYSTEM_NAME_x86 = "qemu-system-i386"
-QB_CPU_x86 = "-cpu qemu32"
-QB_CPU_KVM_x86 = "-cpu kvm32"
+QB_CPU_x86 = "-cpu pentium2"
+QB_CPU_KVM_x86 = "-cpu pentium2"
QB_SYSTEM_NAME_x86-64 = "qemu-system-x86_64"
QB_CPU_x86-64 = "-cpu core2duo"
-QB_CPU_KVM_x86-64 = "-cpu kvm64"
+QB_CPU_KVM_x86-64 = "-cpu core2duo"
QB_AUDIO_DRV = "alsa"
QB_AUDIO_OPT = "-soundhw ac97,es1370"
We've had problems here in the past:
http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=b8819b02dc4ff29d678cc55887dfe6c2d109a67d
http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=a2a20adbfd03ed9f07a3aa38ee2c9a8d962d4bf9
so we once did use core2duo and had to switch away from it after kernel
issues. Admittedly that was some time ago and I don't know if those
issues were resolved. I do remember other debates about qemu32 verses
pentium2 and other tunes as well so I'm a little nervous about changes
in this area as the issues were subtle to track down and fix,
particularly given the range of host distro kernels we need to run kvm
against :(.
Got it; thanks for filling me in. Please let me know if I'm missing
something, but I looked over the bugs and I think they are different
issues (not caused by pentium2 or core2duo settings).
Bug #5817 [1][2] appears to be an issue with passing two -cpu arguments
instead of just one. This didn't actually cause a crash or panic AFAICT,
but it was confusing. It was fixed by always passing in kvm/kvm64 when
--enable-kvm is set.
Bug #3908 [3][4] is caused by an interaction between -cpu host and the
kernel. It makes sense that -cpu host could cause issues like this
because there are no guarantees that the host CPU and the target CPU are
100% compatible. In this bug, some kernels worked and others did not,
which makes sense.
These bug fixes did fix the relevant bugs, but they caused the bug I'm
seeing because they switched to generic CPUs (which advertise very few
CPU features) without switching the actual compile target. Thus we are
building for i586 (pentium2) and core2duo but running with generic CPUs
that don't know about the features we have compiled in. Any program
attempting to use CPU features that were compiled in but not enabled at
runtime are going to crash, and that's exactly what I saw in Qt.
Obviously, a change like this warrants good testing, but by my analysis
it should be safe. If there's some extra testing I can do to help out,
or if there's let me know and I'd be happy to do it.
[1]
http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=a2a20adbfd03ed9f07a3aa38ee2c9a8d962d4bf9
[2] https://bugzilla.yoctoproject.org/show_bug.cgi?id=5817
[3]
http://git.yoctoproject.org/cgit.cgi/poky/commit/?id=b8819b02dc4ff29d678cc55887dfe6c2d109a67d
[4] https://bugzilla.yoctoproject.org/show_bug.cgi?id=3908
--
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