[PATCH v4 0/3] RISC-V: KVM: Guest Debug Support - Software Breakpoint Part

[Chao Du]

This series implements the "KVM Guset Debug" feature on RISC-V. This is
an existing feature which is already supported by some other arches.
It allows us to debug a RISC-V KVM guest from GDB in host side.

As the first stage, the software breakpoints (ebreak instruction) is
implemented. HW breakpoints support will come later after a synthetically
consideration with the SBI debug trigger extension.

A selftest case was added in this series. Manual test was done on QEMU
RISC-V hypervisor emulator. (add '-s' to enable the gdbserver in QEMU)

This series is based on Linux 6.9-rc1 and also available at:
https://github.com/Du-Chao/kvm-riscv/tree/guest_debug_sw_v3_6.9-rc1

The matched QEMU is available at:
https://github.com/Du-Chao/qemu/tree/riscv_gd_sw


Changes from v3->v4:
- Some optimization on the testcase as per review comments.

Changes from v2->v3:
- Rebased on Linux 6.9-rc1.
- Use BIT() in the macro definition.
- set/clear the bit EXC_BREAKPOINT explicitly.
- change the testcase name to ebreak_test.
- test the scenario without GUEST_DEBUG. vm_install_exception_handler()
  is used thanks to Haibo's patch.

Changes from v1->v2:
- Rebased on Linux 6.8-rc6.
- Maintain a hedeleg in "struct kvm_vcpu_config" for each VCPU.
- Update the HEDELEG csr in kvm_arch_vcpu_load().

Changes from RFC->v1:
- Rebased on Linux 6.8-rc2.
- Merge PATCH1 and PATCH2 into one patch.
- kselftest case added.

v3 link:
https://lore.kernel.org/kvm/20240327075526.31855-1-duchao@eswincomputing.com
v2 link:
https://lore.kernel.org/kvm/20240301013545.10403-1-duchao@eswincomputing.com
v1 link:
https://lore.kernel.org/kvm/20240206074931.22930-1-duchao@eswincomputing.com
RFC link:
https://lore.kernel.org/kvm/20231221095002.7404-1-duchao@eswincomputing.com

Chao Du (3):
  RISC-V: KVM: Implement kvm_arch_vcpu_ioctl_set_guest_debug()
  RISC-V: KVM: Handle breakpoint exits for VCPU
  RISC-V: KVM: selftests: Add ebreak test support

 arch/riscv/include/asm/kvm_host.h             | 12 +++
 arch/riscv/kvm/main.c                         | 18 +---
 arch/riscv/kvm/vcpu.c                         | 16 +++-
 arch/riscv/kvm/vcpu_exit.c                    |  4 +
 arch/riscv/kvm/vm.c                           |  1 +
 tools/testing/selftests/kvm/Makefile          |  1 +
 .../testing/selftests/kvm/riscv/ebreak_test.c | 82 +++++++++++++++++++
 7 files changed, 116 insertions(+), 18 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/riscv/ebreak_test.c

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2.17.1