Current lazy fp/simd implementation switches hardware context on guest access and again on exit to host, otherwise context switch is skipped. This patch set builds on that functionality and executes a hardware context switch on first time access and when vCPU is scheduled out or returns to user space (on vcpu_put). For an FP and lmbench load it reduces fp/simd context switch from 30-50% down to near 0%. Results will vary with load but is no worse then current approach. Running floating point application on nearly idle system: ./tst-float 100000uS - (sleep for .1s) fp/simd switch reduced by 99%+ ./tst-float 10000uS - (sleep for 10 ms) reduced by 98%+ ./tst-float 1000uS - (sleep for 1ms) reduced by ~98% ... ./tst-float 1uS - reduced by 2%+ Tested on Juno, Foundation Model, and Fast Models. Test Details: ------------- armv7 - with CONFIG_VFP, CONFIG_NEON, CONFIG_KERNEL_MODE_NEON options enabled: - On host executed 12 fp applications - with ranging sleep intervals - Two guests - with 12 fp processes - with ranging sleep intervals armv8 - Similar to armv7, with mix of 32 and 64 bit guests - on Juno ran 2-32bit and 2-64 bit guests. These patches are based on earlier arm64 fp/simd optimization work - https://lists.cs.columbia.edu/pipermail/kvmarm/2015-July/015748.html And subsequent fixes by Marc and Christoffer at KVM Forum hackathon to handle 32-bit guest on 64 bit host - https://lists.cs.columbia.edu/pipermail/kvmarm/2015-August/016128.html Changes since v5->v6: - Followed up on Christoffers comments o armv7 - replaced fp/simd asm with supported function calls o armv7 - save hcptr once on access instead of every exit o armv7 - removed hcptr macro o armv7 - fixed twisted boolean return logic o armv7 - removed isb after setting fpexec32 since its followed with a hyp call o armv8 - rebased to 4.4-rc5 - wsinc o armv8 - as with hpctpr save cptr_el2 on access instead of every exit o armv7/armv8 - restructured patch series to simplify review Chances since v4->v5: - Followed up on Marcs comments - Removed dirty flag, and used trap bits to check for dirty fp/simd - Seperated host form hyp code - As a consequence for arm64 added a commend assember header file - Fixed up critical accesses to fpexec, and added isb - Converted defines to inline functions Changes since v3->v4: - Followup on Christoffers comments - Move fpexc handling to vcpu_load and vcpu_put - Enable and restore fpexc in EL2 mode when running a 32 bit guest on 64bit EL2 - rework hcptr handling Changes since v2->v3: - combined arm v7 and v8 into one short patch series - moved access to fpexec_el2 back to EL2 - Move host restore to EL1 from EL2 and call directly from host - optimize trap enable code - renamed some variables to match usage Changes since v1->v2: - Fixed vfp/simd trap configuration to enable trace trapping - Removed set_hcptr branch label - Fixed handling of FPEXC to restore guest and host versions on vcpu_put - Tested arm32/arm64 - rebased to 4.3-rc2 - changed a couple register accesses from 64 to 32 bit Mario Smarduch (6): Introduce armv7 fp/simd vcpu fields and helpers Introduce host fp/simd context switch function Enable armv7 fp/simd enhanced context switch Deleted unused macros Introduce armv8 fp/simd vcpu fields and helpers Enable armv8 fp/simd enhanced context switch arch/arm/include/asm/kvm_emulate.h | 54 ++++++++++++++++++++++++++++++++++++ arch/arm/include/asm/kvm_host.h | 8 ++++++ arch/arm/kernel/asm-offsets.c | 1 + arch/arm/kvm/Makefile | 2 +- arch/arm/kvm/arm.c | 19 +++++++++++++ arch/arm/kvm/fpsimd_switch.S | 47 +++++++++++++++++++++++++++++++ arch/arm/kvm/interrupts.S | 43 ++++++++++------------------ arch/arm/kvm/interrupts_head.S | 29 ------------------- arch/arm64/include/asm/kvm_asm.h | 5 ++++ arch/arm64/include/asm/kvm_emulate.h | 30 ++++++++++++++++++++ arch/arm64/include/asm/kvm_host.h | 12 ++++++++ arch/arm64/kernel/asm-offsets.c | 1 + arch/arm64/kvm/hyp/entry.S | 1 + arch/arm64/kvm/hyp/hyp-entry.S | 26 +++++++++++++++++ arch/arm64/kvm/hyp/switch.c | 26 ++--------------- 15 files changed, 222 insertions(+), 82 deletions(-) create mode 100644 arch/arm/kvm/fpsimd_switch.S -- 1.9.1 -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
