Re: [PATCH v3] target/riscv: Clearing the CSR values at reset and syncing the MPSTATE with the host

[Alistair Francis <alistair23@gmail.com>]

On Mon, Jul 24, 2023 at 2:26 AM liguang.zhang <18622748025@163.com> wrote:
>
> From: "liguang.zhang" <liguang.zhang@hexintek.com>
>
> Fix the guest reboot error when using KVM
> There are two issues when rebooting a guest using KVM
> 1. When the guest initiates a reboot the host is unable to stop the vcpu
> 2. When running a SMP guest the qemu monitor system_reset causes a vcpu crash
>
> This can be fixed by clearing the CSR values at reset and syncing the
> MPSTATE with the host.
>
> Signed-off-by: liguang.zhang <liguang.zhang@hexintek.com>
> ---
>  target/riscv/kvm.c       | 42 ++++++++++++++++++++++++++++++++++++++++
>  target/riscv/kvm_riscv.h |  1 +
>  2 files changed, 43 insertions(+)
>
> diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c
> index 9d8a8982f9..ecc8ab8238 100644
> --- a/target/riscv/kvm.c
> +++ b/target/riscv/kvm.c
> @@ -44,6 +44,8 @@
>  #include "migration/migration.h"
>  #include "sysemu/runstate.h"
>
> +static bool cap_has_mp_state;
> +
>  static uint64_t kvm_riscv_reg_id(CPURISCVState *env, uint64_t type,
>                                   uint64_t idx)
>  {
> @@ -790,6 +792,24 @@ int kvm_arch_get_registers(CPUState *cs)
>      return ret;
>  }
>
> +int kvm_riscv_sync_mpstate_to_kvm(RISCVCPU *cpu, int state)
> +{
> +    if (cap_has_mp_state) {
> +        struct kvm_mp_state mp_state = {
> +            .mp_state = state
> +        };
> +
> +        int ret = kvm_vcpu_ioctl(CPU(cpu), KVM_SET_MP_STATE, &mp_state);
> +        if (ret) {
> +            fprintf(stderr, "%s: failed to sync MP_STATE %d/%s\n",
> +                    __func__, ret, strerror(-ret));
> +            return -1;
> +        }
> +    }
> +
> +    return 0;
> +}
> +
>  int kvm_arch_put_registers(CPUState *cs, int level)
>  {
>      int ret = 0;
> @@ -809,6 +829,18 @@ int kvm_arch_put_registers(CPUState *cs, int level)
>          return ret;
>      }
>
> +    if (KVM_PUT_RESET_STATE == level) {
> +        RISCVCPU *cpu = RISCV_CPU(cs);
> +        if (cs->cpu_index == 0) {
> +            ret = kvm_riscv_sync_mpstate_to_kvm(cpu, KVM_MP_STATE_RUNNABLE);
> +        } else {
> +            ret = kvm_riscv_sync_mpstate_to_kvm(cpu, KVM_MP_STATE_STOPPED);
> +        }
> +        if (ret) {
> +            return ret;
> +        }
> +    }

You are adding code to kvm_arch_put_registers() don't you also need to
add code to kvm_arch_get_registers()? and a *_mpstate_to_qemu()
function to match?

Alistair

> +
>      return ret;
>  }
>
> @@ -909,6 +941,7 @@ int kvm_arch_add_msi_route_post(struct kvm_irq_routing_entry *route,
>
>  int kvm_arch_init(MachineState *ms, KVMState *s)
>  {
> +    cap_has_mp_state = kvm_check_extension(s, KVM_CAP_MP_STATE);
>      return 0;
>  }
>
> @@ -987,10 +1020,19 @@ void kvm_riscv_reset_vcpu(RISCVCPU *cpu)
>      if (!kvm_enabled()) {
>          return;
>      }
> +    for (int i=0; i<32; i++)
> +        env->gpr[i] = 0;
>      env->pc = cpu->env.kernel_addr;
>      env->gpr[10] = kvm_arch_vcpu_id(CPU(cpu)); /* a0 */
>      env->gpr[11] = cpu->env.fdt_addr;          /* a1 */
>      env->satp = 0;
> +    env->mie = 0;
> +    env->stvec = 0;
> +    env->sscratch = 0;
> +    env->sepc = 0;
> +    env->scause = 0;
> +    env->stval = 0;
> +    env->mip = 0;
>  }
>
>  void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level)
> diff --git a/target/riscv/kvm_riscv.h b/target/riscv/kvm_riscv.h
> index e3ba935808..3ea68c38e3 100644
> --- a/target/riscv/kvm_riscv.h
> +++ b/target/riscv/kvm_riscv.h
> @@ -22,5 +22,6 @@
>  void kvm_riscv_init_user_properties(Object *cpu_obj);
>  void kvm_riscv_reset_vcpu(RISCVCPU *cpu);
>  void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level);
> +int kvm_riscv_sync_mpstate_to_kvm(RISCVCPU *cpu, int state);
>
>  #endif
> --
> 2.41.0
>