[PATCH v2 0/3] RISC-V: KVM: Guest Debug Support - Software Breakpoint Part

[Chao Du <duchao@eswincomputing.com>]

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 6.8-rc6 and also available at:
https://github.com/Du-Chao/kvm-riscv/tree/guest_debug_sw_v2

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

Please note that if Paolo's change
https://lore.kernel.org/kvm/20240131233056.10845-8-pbonzini at redhat.com/
is adopted, then we can keep 'arch/riscv/include/uapi/asm/kvm.h'
untouched.

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.

v1 link:
https://lore.kernel.org/kvm/20240206074931.22930-1-duchao at eswincomputing.com
RFC link:
https://lore.kernel.org/kvm/20231221095002.7404-1-duchao at 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 breakpoints test support

 arch/riscv/include/asm/kvm_host.h             | 17 +++++++
 arch/riscv/include/uapi/asm/kvm.h             |  1 +
 arch/riscv/kvm/main.c                         | 18 +------
 arch/riscv/kvm/vcpu.c                         | 15 +++++-
 arch/riscv/kvm/vcpu_exit.c                    |  4 ++
 arch/riscv/kvm/vm.c                           |  1 +
 tools/testing/selftests/kvm/Makefile          |  1 +
 .../testing/selftests/kvm/riscv/breakpoints.c | 49 +++++++++++++++++++
 8 files changed, 88 insertions(+), 18 deletions(-)
 create mode 100644 tools/testing/selftests/kvm/riscv/breakpoints.c

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2.17.1