LBR and Virtualization

Yoav_A_ — Mon, 28 Jul 2014 17:40:16 GMT

I'm using LBR to trace guest execution, each time before vm_enter I overwrite the MSR_LASTBRANCH_(N-1)_FROM_IP/TO values with a magic value (0xdeadbabe) and execute a few instructions and read out the values. sometimes a record is skipped in the LBR and contains the magic value.
why would this ever happen? I've look at the errata for haswell and didn't see anything similar, and running a similar code on the host outputs a perfect sequential trace. could this be an hardware bug related to vmx?
Regards
Yoav

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Quoc-Thai_L_Intel — Mon, 11 Aug 2014 17:12:25 GMT

You might want to check with open-source community to see how they would handle the issue that you are having.

Here are some examples of Virtualization code:

Citrix XenServer*: http://www.citrix.com/products/xenserver/overview.html
Xen* project: http://www.xenproject.org/

-Thai

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LBR and Virtualization

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