[PATCH v4 0/2] arm/arm64: KVM: Optimize arm64 fp/simd, saves 30-50% on exits

Mario Smarduch m.smarduch at samsung.com
Thu Jul 16 14:29:36 PDT 2015

Currently we save/restore fp/simd on each exit. The first patch optimizes arm64
save/restore, we only do so on Guest access. hackbench and several lmbench
tests show anywhere from 30% to 50% of exits don't context switch the vfp/simd

For second patch 32-bit handler is updated to keep exit handling consistent
with 64-bit code.

Changes since v3:
- Per Christoffers comment - changed comment for skip fp/simd in patch 1/2
- Changed cover text, clarify optimization in the context of this patch 

Changes since v2:
- Only for patch 2/2
  - Removed load_vcpu in switch_to_guest_vfp per Marcs comment
  - Got another chance to replace an unreferenced label with a comment

Changes since v1:
- only for patch 2/2
  - Reworked trapping to vfp access handler

Changes since inital version:
- Addressed Marcs comments
- Verified optimization improvements with lmbench and hackbench, updated
  commit message

Mario Smarduch (2):
  Optimize arm64 skip 30-50% vfp/simd save/restore on exits
  keep arm vfp/simd exit handling consistent with arm64

 arch/arm/kvm/interrupts.S        | 14 +++++++------
 arch/arm64/include/asm/kvm_arm.h |  5 ++++-
 arch/arm64/kvm/hyp.S             | 45 +++++++++++++++++++++++++++++++++++++---
 3 files changed, 54 insertions(+), 10 deletions(-)


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