Hi, Major changes since v2 (Based on Will's feedback) -Dropped adding a new static key and cpufeature for retrieving supported VMID bits. Instead, we now make use of the kvm_arm_vmid_bits variable (patch #2). -Since we expect less frequent rollover in the case of VMIDs, the TLB invalidation is now broadcasted on rollover instead of keeping per CPU flush_pending info and issuing a local context flush. -Clear active_vmids on vCPU schedule out to avoid unnecessarily reserving the VMID space(patch #3). -I have kept the struct kvm_vmid as it is for now(instead of a typedef as suggested), as we may soon add another variable to it when we introduce Pinned KVM VMID support. Sanity tested on HiSilicon D06 board. Thanks, Shameer RFCv1 --> v2 - Dropped "pinned VMID" support for now. - Dropped RFC tag. History(from RFC v1): ------------------- Please find the RFC series here, https://lore.kernel.org/kvmarm/20210506165232.1969-1-shameerali.kolothum.thodi@xxxxxxxxxx/ This is based on a suggestion from Will [0] to try out the asid based kvm vmid solution as a separate VMID allocator instead of the shared lib approach attempted in v4[1]. The idea is to compare both the approaches and see whether the shared lib solution with callbacks make sense or not. Though we are not yet using the pinned vmids yet, patch #2 has code for pinned vmid support. This is just to help the comparison. Test Setup/Results ---------------- The measurement was made with maxcpus set to 8 and with the number of VMID limited to 4-bit. The test involves running concurrently 40 guests with 2 vCPUs. Each guest will then execute hackbench 5 times before exiting. The performance difference between the current algo and the new one are(avg. of 10 runs): - 1.9% less entry/exit from the guest - 0.5% faster This is more or less comparable to v4 numbers. For the complete series, please see, https://github.com/hisilicon/kernel-dev/tree/private-v5.12-rc7-vmid-2nd-rfc and for the shared asid lib v4 solution, https://github.com/hisilicon/kernel-dev/tree/private-v5.12-rc7-asid-v4 As you can see there are ofcourse code duplication with this approach but may be it is more easy to maintain considering the complexity involved. Please take a look and let me know your feedback. Thanks, Shameer Julien Grall (1): KVM: arm64: Align the VMID allocation with the arm64 ASID one Shameer Kolothum (3): KVM: arm64: Introduce a new VMID allocator for KVM KVM: arm64: Make VMID bits accessible outside of allocator KVM: arm64: Clear active_vmids on vCPU schedule out arch/arm64/include/asm/kvm_host.h | 10 +- arch/arm64/include/asm/kvm_mmu.h | 4 +- arch/arm64/kernel/image-vars.h | 3 + arch/arm64/kvm/Makefile | 2 +- arch/arm64/kvm/arm.c | 122 +++++------------ arch/arm64/kvm/hyp/nvhe/mem_protect.c | 3 +- arch/arm64/kvm/mmu.c | 1 - arch/arm64/kvm/vmid.c | 182 ++++++++++++++++++++++++++ 8 files changed, 228 insertions(+), 99 deletions(-) create mode 100644 arch/arm64/kvm/vmid.c -- 2.17.1 _______________________________________________ kvmarm mailing list kvmarm@xxxxxxxxxxxxxxxxxxxxx https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
