Re: [PATCH 00/27] KVM PPC PV framework

On Thu, Jul 1, 2010 at 4:12 PM, Alexander Graf [off-list ref] wrote:

On PPC we run PR=3D0 (kernel mode) code in PR=3D1 (user mode) and don't u=

se the

hypervisor extensions.

While that is all great to show that virtualization is possible, there ar=

e

quite some cases where the emulation overhead of privileged instructions =

is

killing performance.

This patchset tackles exactly that issue. It introduces a paravirtual fra=

mework

using which KVM and Linux share a page to exchange register state with. T=

hat

KVM and Linux or KVM and GuestOS ?

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 ag=

ainst

the PV framework. Here are the results:

[without]

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

; done

real =A0 =A00m14.659s
user =A0 =A00m8.967s
sys =A0 =A0 0m5.688s

[with]

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

; done

real =A0 =A00m7.557s
user =A0 =A00m4.121s
sys =A0 =A0 0m3.426s


So this is a significant performance improvement! I'm quite happy how fas=

t this

whole thing becomes :)

I tried to take all comments I've heard from people so far about such a P=

V

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.

Now go and have fun with fast VMs on PPC! Get yourself a G5 on ebay and s=

tart

experiencing the power yourself. - heh

v1 -> v2:

=A0- change hypervisor calls to use r0 and r3
=A0- make crit detection only trigger in supervisor mode
=A0- RMO -> PAM
=A0- introduce kvm_patch_ins
=A0- only flush icache when patching
=A0- introduce kvm_patch_ins_b
=A0- update documentation

Alexander Graf (27):
=A0KVM: PPC: Introduce shared page
=A0KVM: PPC: Convert MSR to shared page
=A0KVM: PPC: Convert DSISR to shared page
=A0KVM: PPC: Convert DAR to shared page.
=A0KVM: PPC: Convert SRR0 and SRR1 to shared page
=A0KVM: PPC: Convert SPRG[0-4] to shared page
=A0KVM: PPC: Implement hypervisor interface
=A0KVM: PPC: Add PV guest critical sections
=A0KVM: PPC: Add PV guest scratch registers
=A0KVM: PPC: Tell guest about pending interrupts
=A0KVM: PPC: Make RMO a define
=A0KVM: PPC: First magic page steps
=A0KVM: PPC: Magic Page Book3s support
=A0KVM: PPC: Magic Page BookE support
=A0KVM: PPC: Expose magic page support to guest
=A0KVM: Move kvm_guest_init out of generic code
=A0KVM: PPC: Generic KVM PV guest support
=A0KVM: PPC: KVM PV guest stubs
=A0KVM: PPC: PV instructions to loads and stores
=A0KVM: PPC: PV tlbsync to nop
=A0KVM: PPC: Introduce kvm_tmp framework
=A0KVM: PPC: Introduce branch patching helper
=A0KVM: PPC: PV assembler helpers
=A0KVM: PPC: PV mtmsrd L=3D1
=A0KVM: PPC: PV mtmsrd L=3D0 and mtmsr
=A0KVM: PPC: PV wrteei
=A0KVM: PPC: Add Documentation about PV interface

=A0Documentation/kvm/ppc-pv.txt =A0 =A0 =A0 =A0 =A0 =A0 | =A0185 ++++++++=

++++++

=A0arch/powerpc/include/asm/kvm_book3s.h =A0 =A0| =A0 =A01 -
=A0arch/powerpc/include/asm/kvm_host.h =A0 =A0 =A0| =A0 15 +-
=A0arch/powerpc/include/asm/kvm_para.h =A0 =A0 =A0| =A0121 +++++++++-
=A0arch/powerpc/include/asm/kvm_ppc.h =A0 =A0 =A0 | =A0 =A01 +
=A0arch/powerpc/kernel/Makefile =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A02 +
=A0arch/powerpc/kernel/asm-offsets.c =A0 =A0 =A0 =A0| =A0 18 ++-
=A0arch/powerpc/kernel/kvm.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0408 ++++=

++++++++++++++++++++++++++

=A0arch/powerpc/kernel/kvm_emul.S =A0 =A0 =A0 =A0 =A0 | =A0237 ++++++++++=

+++++++

=A0arch/powerpc/kvm/44x.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A07 =

+

=A0arch/powerpc/kvm/44x_tlb.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A08 +-
=A0arch/powerpc/kvm/book3s.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0165 ++++=

++++-----

=A0arch/powerpc/kvm/book3s_32_mmu.c =A0 =A0 =A0 =A0 | =A0 28 ++-
=A0arch/powerpc/kvm/book3s_32_mmu_host.c =A0 =A0| =A0 16 +-
=A0arch/powerpc/kvm/book3s_64_mmu.c =A0 =A0 =A0 =A0 | =A0 42 +++-
=A0arch/powerpc/kvm/book3s_64_mmu_host.c =A0 =A0| =A0 16 +-
=A0arch/powerpc/kvm/book3s_emulate.c =A0 =A0 =A0 =A0| =A0 25 +-
=A0arch/powerpc/kvm/book3s_paired_singles.c | =A0 11 +-
=A0arch/powerpc/kvm/booke.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0113 ++++=

+++--

=A0arch/powerpc/kvm/booke.h =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A06 +-
=A0arch/powerpc/kvm/booke_emulate.c =A0 =A0 =A0 =A0 | =A0 14 +-
=A0arch/powerpc/kvm/booke_interrupts.S =A0 =A0 =A0| =A0 =A03 +-
=A0arch/powerpc/kvm/e500.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A07 =

+

=A0arch/powerpc/kvm/e500_tlb.c =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 31 ++-
=A0arch/powerpc/kvm/e500_tlb.h =A0 =A0 =A0 =A0 =A0 =A0 =A0| =A0 =A02 +-
=A0arch/powerpc/kvm/emulate.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 47 +++-
=A0arch/powerpc/kvm/powerpc.c =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 42 +++-
=A0arch/powerpc/platforms/Kconfig =A0 =A0 =A0 =A0 =A0 | =A0 10 +
=A0arch/x86/include/asm/kvm_para.h =A0 =A0 =A0 =A0 =A0| =A0 =A06 +
=A0include/linux/kvm_para.h =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 | =A0 =A07 +-
=A030 files changed, 1420 insertions(+), 174 deletions(-)
=A0create mode 100644 Documentation/kvm/ppc-pv.txt
=A0create mode 100644 arch/powerpc/kernel/kvm.c
=A0create mode 100644 arch/powerpc/kernel/kvm_emul.S

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