[PATCH 00/27] KVM PPC PV framework v3

Alexander Graf agraf at suse.de
Thu Jul 29 22:47:41 EST 2010

On PPC we run PR=0 (kernel mode) code in PR=1 (user mode) and don't use the
hypervisor extensions.

While that is all great to show that virtualization is possible, there are
quite some cases where the emulation overhead of privileged instructions is
killing performance.

This patchset tackles exactly that issue. It introduces a paravirtual framework
using which KVM and Linux share a page to exchange register state with. That
way we don't have to switch to the hypervisor just to change a value of a
privileged register.

To prove my point, I ran the same test I did for the MMU optimizations against
the PV framework. Here are the results:


debian-powerpc:~# time for i in {1..1000}; do /bin/echo hello > /dev/null; done

real    0m14.659s
user    0m8.967s
sys     0m5.688s


debian-powerpc:~# time for i in {1..1000}; do /bin/echo hello > /dev/null; done

real    0m7.557s
user    0m4.121s
sys     0m3.426s

So this is a significant performance improvement! I'm quite happy how fast this
whole thing becomes :)

I tried to take all comments I've heard from people so far about such a PV
framework into account. In case you told me something before that is a no-go
and I still did it, please just tell me again.

To make use of this whole thing you also need patches to qemu and openbios. I
have them in my queue, but want to see this set upstream first before I start
sending patches to the other projects.

Now go and have fun with fast VMs on PPC! Get yourself a G5 on ebay and start
experiencing the power yourself. - heh

v1 -> v2:

  - change hypervisor calls to use r0 and r3
  - make crit detection only trigger in supervisor mode
  - RMO -> PAM
  - introduce kvm_patch_ins
  - only flush icache when patching
  - introduce kvm_patch_ins_b
  - update documentation

v2 -> v3:

  - use pPAPR conventions for hypercall interface
  - only use r0 as magic sc number
  - remove PVR detection
  - remove BookE shared page mapping support
  - combine book3s-64 and -32 magic page ra override
  - add self-test check if the mapping works to guest code
  - add safety check for relocatable kernels

Alexander Graf (27):
  KVM: PPC: Introduce shared page
  KVM: PPC: Convert MSR to shared page
  KVM: PPC: Convert DSISR to shared page
  KVM: PPC: Convert DAR to shared page.
  KVM: PPC: Convert SRR0 and SRR1 to shared page
  KVM: PPC: Convert SPRG[0-4] to shared page
  KVM: PPC: Implement hypervisor interface
  KVM: PPC: Add PV guest critical sections
  KVM: PPC: Add PV guest scratch registers
  KVM: PPC: Tell guest about pending interrupts
  KVM: PPC: Make PAM a define
  KVM: PPC: First magic page steps
  KVM: PPC: Magic Page Book3s support
  KVM: PPC: Expose magic page support to guest
  KVM: Move kvm_guest_init out of generic code
  KVM: PPC: Generic KVM PV guest support
  KVM: PPC: KVM PV guest stubs
  KVM: PPC: PV instructions to loads and stores
  KVM: PPC: PV tlbsync to nop
  KVM: PPC: Introduce kvm_tmp framework
  KVM: PPC: Introduce branch patching helper
  KVM: PPC: PV assembler helpers
  KVM: PPC: PV mtmsrd L=1
  KVM: PPC: PV mtmsrd L=0 and mtmsr
  KVM: PPC: PV wrteei
  KVM: PPC: Add Documentation about PV interface
  KVM: PPC: Add get_pvinfo interface to query hypercall instructions

 Documentation/kvm/api.txt                |   23 ++
 Documentation/kvm/ppc-pv.txt             |  180 +++++++++++
 arch/powerpc/include/asm/kvm_book3s.h    |    2 +-
 arch/powerpc/include/asm/kvm_host.h      |   15 +-
 arch/powerpc/include/asm/kvm_para.h      |  135 ++++++++-
 arch/powerpc/include/asm/kvm_ppc.h       |    1 +
 arch/powerpc/kernel/Makefile             |    2 +
 arch/powerpc/kernel/asm-offsets.c        |   18 +-
 arch/powerpc/kernel/kvm.c                |  485 ++++++++++++++++++++++++++++++
 arch/powerpc/kernel/kvm_emul.S           |  247 +++++++++++++++
 arch/powerpc/kvm/44x.c                   |    7 +
 arch/powerpc/kvm/44x_tlb.c               |    8 +-
 arch/powerpc/kvm/book3s.c                |  188 ++++++++----
 arch/powerpc/kvm/book3s_32_mmu.c         |   28 ++-
 arch/powerpc/kvm/book3s_32_mmu_host.c    |    6 +-
 arch/powerpc/kvm/book3s_64_mmu.c         |   42 +++-
 arch/powerpc/kvm/book3s_64_mmu_host.c    |   13 +-
 arch/powerpc/kvm/book3s_emulate.c        |   25 +-
 arch/powerpc/kvm/book3s_paired_singles.c |   11 +-
 arch/powerpc/kvm/booke.c                 |   83 ++++--
 arch/powerpc/kvm/booke.h                 |    6 +-
 arch/powerpc/kvm/booke_emulate.c         |   14 +-
 arch/powerpc/kvm/booke_interrupts.S      |    3 +-
 arch/powerpc/kvm/e500.c                  |    7 +
 arch/powerpc/kvm/e500_tlb.c              |   12 +-
 arch/powerpc/kvm/e500_tlb.h              |    2 +-
 arch/powerpc/kvm/emulate.c               |   36 ++-
 arch/powerpc/kvm/powerpc.c               |   84 +++++-
 arch/powerpc/platforms/Kconfig           |   10 +
 arch/x86/include/asm/kvm_para.h          |    6 +
 include/linux/kvm.h                      |   11 +
 include/linux/kvm_para.h                 |    7 +-
 32 files changed, 1538 insertions(+), 179 deletions(-)
 create mode 100644 Documentation/kvm/ppc-pv.txt
 create mode 100644 arch/powerpc/kernel/kvm.c
 create mode 100644 arch/powerpc/kernel/kvm_emul.S

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