On physical machine, ipi HW uses IOCSR registers, however there is trap into hypervisor when vcpu accesses IOCSR registers if system is in VM mode. SWI is a interrupt mechanism like SGI on ARM, software can send interrupt to CPU, only that on LoongArch SWI can only be sent to local CPU now. So SWI can not used for IPI on real HW system, however it can be used on VM when combined with hypercall method. IPI can be sent with hypercall method and SWI interrupt is injected to vcpu, vcpu can treat SWI interrupt as IPI. With PV IPI supported, there is one trap with IPI sending, however with IPI receiving there is no trap. with IOCSR HW ipi method, there will be one trap with IPI sending and two trap with ipi receiving. Also IPI multicast support is added for VM, the idea comes from x86 PV ipi. IPI can be sent to 128 vcpus in one time. With IPI multicast support, trap will be reduced greatly. Here is the microbenchmarck data with "perf bench futex wake" testcase on 3C5000 single-way machine, there are 16 cpus on 3C5000 single-way machine, VM has 16 vcpus also. The benchmark data is ms time unit to wakeup 16 threads, the performance is better if data is smaller. physical machine 0.0176 ms VM original 0.1140 ms VM with pv ipi patch 0.0481 ms It passes to boot with 128/256 vcpus, and passes to run runltp command with package ltp-20230516. --- v7 --- v8: 1. Remove kernel PLV mode checking with cpucfg emulation for hypervisor feature inquiry. 2. Remove document about loongarch hypercall ABI per request of huacai, will add English/Chinese doc at the same time in later. v6 --- v7: 1. Refine LoongArch virt document by review comments. 2. Add function kvm_read_reg()/kvm_write_reg() in hypercall emulation, and later it can be used for other trap emulations. v5 --- v6: 1. Add privilege checking when emulating cpucfg at index 0x4000000 -- 0x400000FF, return 0 if not executed at kernel mode. 2. Add document about LoongArch pv ipi with new creatly directory Documentation/virt/kvm/loongarch/ 3. Fix pv ipi handling in kvm backend function kvm_pv_send_ipi(), where min should plus BITS_PER_LONG with second bitmap, otherwise VM with more than 64 vpus fails to boot. 4. Adjust patch order and code refine with review comments. v4 --- v5: 1. Refresh function/macro name from review comments. v3 --- v4: 1. Modfiy pv ipi hook function name call_func_ipi() and call_func_single_ipi() with send_ipi_mask()/send_ipi_single(), since pv ipi is used for both remote function call and reschedule notification. 2. Refresh changelog. v2 --- v3: 1. Add 128 vcpu ipi multicast support like x86 2. Change cpucfg base address from 0x10000000 to 0x40000000, in order to avoid confliction with future hw usage 3. Adjust patch order in this patchset, move patch Refine-ipi-ops-on-LoongArch-platform to the first one. v1 --- v2: 1. Add hw cpuid map support since ipi routing uses hw cpuid 2. Refine changelog description 3. Add hypercall statistic support for vcpu 4. Set percpu pv ipi message buffer aligned with cacheline 5. Refine pv ipi send logic, do not send ipi message with if there is pending ipi message. --- Bibo Mao (6): LoongArch/smp: Refine some ipi functions on LoongArch platform LoongArch: KVM: Add hypercall instruction emulation support LoongArch: KVM: Add cpucfg area for kvm hypervisor LoongArch: KVM: Add vcpu search support from physical cpuid LoongArch: KVM: Add pv ipi support on kvm side LoongArch: Add pv ipi support on guest kernel side arch/loongarch/Kconfig | 9 + arch/loongarch/include/asm/Kbuild | 1 - arch/loongarch/include/asm/hardirq.h | 5 + arch/loongarch/include/asm/inst.h | 1 + arch/loongarch/include/asm/irq.h | 10 +- arch/loongarch/include/asm/kvm_host.h | 27 +++ arch/loongarch/include/asm/kvm_para.h | 155 ++++++++++++++++++ arch/loongarch/include/asm/kvm_vcpu.h | 11 ++ arch/loongarch/include/asm/loongarch.h | 11 ++ arch/loongarch/include/asm/paravirt.h | 27 +++ .../include/asm/paravirt_api_clock.h | 1 + arch/loongarch/include/asm/smp.h | 31 ++-- arch/loongarch/include/uapi/asm/Kbuild | 2 - arch/loongarch/kernel/Makefile | 1 + arch/loongarch/kernel/irq.c | 24 +-- arch/loongarch/kernel/paravirt.c | 151 +++++++++++++++++ arch/loongarch/kernel/perf_event.c | 14 +- arch/loongarch/kernel/smp.c | 62 ++++--- arch/loongarch/kernel/time.c | 12 +- arch/loongarch/kvm/exit.c | 132 +++++++++++++-- arch/loongarch/kvm/vcpu.c | 94 ++++++++++- arch/loongarch/kvm/vm.c | 11 ++ 22 files changed, 690 insertions(+), 102 deletions(-) create mode 100644 arch/loongarch/include/asm/kvm_para.h create mode 100644 arch/loongarch/include/asm/paravirt.h create mode 100644 arch/loongarch/include/asm/paravirt_api_clock.h delete mode 100644 arch/loongarch/include/uapi/asm/Kbuild create mode 100644 arch/loongarch/kernel/paravirt.c base-commit: 5eb4573ea63d0c83bf58fb7c243fc2c2b6966c02 -- 2.39.3
