[Xen-devel] [PATCH 0/8] Various VPMU patches

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

Here is a set of VPMU changes that I thought might be useful.

The first two patches are to avoid VMEXITs on certain MSR accesses. This
is already part of VMX so I added similar SVM code

The third patch should address the problem that Suravee mentioned on the
list a few weeks ago 
(http://lists.xen.org/archives/html/xen-devel/2013-03/msg00087.html). 
It's a slightly different solution then what he suggested.

4th patch stops counters on AMD when VCPU is de-scheduled

5th is trivial Haswell support (new model number)

6th patch is trying to factor out common code from VMX and SVM.

7th is lazy VPMU save/restore. It is optimized for the case when CPUs are
not over-subscribed and VCPU stays on the same processor most of the time.
It is more beneficial on Intel processors because HW will keep track of
guest/host global control register in VMCS and tehrefore we don't need to
explicitly stop the counters. On AMD we do need to do this and so while
there is improvement, it is not as pronounced.

Here are some numbers that I managed to collect while running guests with
oprofile. This is number of executed instructions in vpmu_save/vpmu_load.

              Eager VPMU                 Lazy VPMU
           Save      Restore       Save      Restore
Intel      181       225            46         50
AMD        132       104            80        102

When processors are oversubscribed, lazy restore may take about 2.5 times
as many instructions as in the dedicated case if new VCPU jumps onto the 
processor (which doesn't happen on every context switch). 


-boris


Boris Ostrovsky (8):
  x86/AMD: Allow more fine-grained control of VMCB MSR Permission Map
  x86/AMD: Do not intercept access to performance counters MSRs
  x86/AMD: Read VPMU MSRs from context when it is not loaded into HW
  x86/AMD: Stop counters on VPMU save
  x86/VPMU: Add Haswell support
  x86/VPMU: Factor out VPMU common code
  x86/VPMU: Save/restore VPMU only when necessary
  x86/AMD: Clean up context_update() in AMD VPMU code

 xen/arch/x86/domain.c                    |  14 ++-
 xen/arch/x86/hvm/svm/svm.c               |  19 ++--
 xen/arch/x86/hvm/svm/vpmu.c              | 188 +++++++++++++++++++++++--------
 xen/arch/x86/hvm/vmx/vmx.c               |   2 -
 xen/arch/x86/hvm/vmx/vpmu_core2.c        |  48 ++++----
 xen/arch/x86/hvm/vpmu.c                  | 114 +++++++++++++++++--
 xen/include/asm-x86/hvm/svm/vmcb.h       |   8 +-
 xen/include/asm-x86/hvm/vmx/vpmu_core2.h |   1 -
 xen/include/asm-x86/hvm/vpmu.h           |   6 +-
 9 files changed, 296 insertions(+), 104 deletions(-)

-- 
1.8.1.2


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