David, On 06.09.12 00:07:52, Peter Zijlstra wrote: > On Wed, 2012-09-05 at 09:43 -0600, David Ahern wrote: > > We need to require exclude_guest when using precise attribute with perf > > else all running VMs on Intel-based servers will crash. I do not have an > > AMD based server to even attempt the preferred solution.
do you have a perf tool patch ready that enables exclude_guest per default for precise events? I have ibs kernel code that returns EINVAL in this case. Current perf tool should then fall back by sending another syscall with the exclude_guest modifier disabled. This should work for ibs. Testing your patch wouln't be an effort for me. To prevent Intel-based servers from crashing, pebs should be only enabled if the exclude_guest modifier is enabled. I guess there is already kernel code to prevent this, but didn't look at the sources. To prevent probing the kernel with syscalls to detect pmu features, I suggested some time ago to introduce /sys/bus/event_source/devices/*/flags or so similar to /proc/cpuinfo:flags. Any opinions on that? There is also the option to emulate exclude_guest for ibs in software. So far I didn't have the time to look at this. We could still add this in the future. Since we need to fix current mainline anyway where such a patch wouldn't go in for v3.6, I will send my current ibs kernel fixes I mentioned above next days. It would be great to test this also with your patch. Thanks, -Robert -- Advanced Micro Devices, Inc. Operating System Research Center -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
