Re: [PATCH] KVM: VMX: enable LBR virtualization

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Does it depend on vPMU _for Linux guests_ or in general?  My impression
is that LBR can be used by the guest independent of the PMU.

   I think only for Linux guests.

   I googled how to enable LBR on other guests(except Linux guests),
   e.g. Windows, and got no developer manuals about it.

   Here is an article about it:
   http://www.codeproject.com/Articles/517466/Last-branch-records-
   and-branch-tracing
   it says:
   "bit 8 of DR7 represents bit 0 of DebugCtl. This is the LBR bit."

Don't worry about the operating system in the guest: you are just
emulating a processor feature, you do not care about anything except
what is written in the Intel SDM.

You can use kvm-unit-tests
(https://git.kernel.org/cgit/virt/kvm/kvm-unit-tests.git/) to write a
test for your feature.  There are existing tests for debugging features.

  ok.

  Regards,

  Jian





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