linux-kernel - [PATCH v4 0/6] LoongArch: Add pv ipi support on LoongArch VM

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Date: Thu,  1 Feb 2024 11:19:44 +0800
From: Bibo Mao <maobibo@...ngson.cn>
To: Huacai Chen <chenhuacai@...nel.org>,
	Tianrui Zhao <zhaotianrui@...ngson.cn>,
	Juergen Gross <jgross@...e.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Cc: loongarch@...ts.linux.dev,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux.dev,
	kvm@...r.kernel.org
Subject: [PATCH v4 0/6] LoongArch: Add pv ipi support on LoongArch VM

This patchset adds pv ipi support for VM. 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. This patch uses SWI interrupt for IPI mechanism, SWI
injection uses hypercall method. And there is one trap with IPI sending,
however with IPI receiving there is no trap. with IOCSR HW ipi method,
there will be two trap into hypervisor with ipi receiving.

Also this patch adds IPI multicast support for VM, this idea comes from
x86 pv ipi. IPI can be sent to 128 vcpus in one time.

Here is the microbenchmarck data with perf bench futex wake case 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 higher if data is smaller.

perf bench futex wake, Wokeup 16 of 16 threads in ms
--physical machine--   --VM original--   --VM with pv ipi patch--
  0.0176 ms               0.1140 ms            0.0481 ms

---
Change in 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.

Change in 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.

Change in 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 ipi ops on LoongArch platform
  LoongArch: KVM: Add hypercall instruction emulation support
  LoongArch: KVM: Add cpucfg area for kvm hypervisor
  LoongArch: Add paravirt interface for guest kernel
  LoongArch: KVM: Add vcpu search support from physical cpuid
  LoongArch: Add pv ipi support on LoongArch system

 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         | 157 ++++++++++++++++++
 arch/loongarch/include/asm/kvm_vcpu.h         |   1 +
 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              | 154 +++++++++++++++++
 arch/loongarch/kernel/perf_event.c            |  14 +-
 arch/loongarch/kernel/setup.c                 |   2 +
 arch/loongarch/kernel/smp.c                   |  60 ++++---
 arch/loongarch/kernel/time.c                  |  12 +-
 arch/loongarch/kvm/exit.c                     | 125 ++++++++++++--
 arch/loongarch/kvm/vcpu.c                     |  94 ++++++++++-
 arch/loongarch/kvm/vm.c                       |  11 ++
 23 files changed, 678 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: 1bbb19b6eb1b8685ab1c268a401ea64380b8bbcb
-- 
2.39.3