[PATCH] target/riscv: fix the issue of guest reboot then no response or crash in kvm-mode

[liguang.zhang]

From: "liguang.zhang" <liguang.zhang@hexintek.com>

kernel log
```shell
reboot

The system is going down NOW!
Sent SIGTERM to all processes
logout
Sent SIGKILL to all processes
Requesting system reboot

```
then no response

for qemu command:
system_reset:

kernel log:
```shell
[   53.739556] kvm [150]: VCPU exit error -95
[   53.739563] kvm [148]: VCPU exit error -95
[   53.739557] kvm [149]: VCPU exit error -95
[   53.740957] kvm [149]: SEPC=0x0 SSTATUS=0x200004120 HSTATUS=0x2002001c0
[   53.740957] kvm [148]: SEPC=0x0 SSTATUS=0x200004120 HSTATUS=0x2002001c0
[   53.741054] kvm [148]: SCAUSE=0x14 STVAL=0x0 HTVAL=0x0 HTINST=0x0
[   53.741058] kvm [149]: SCAUSE=0x14 STVAL=0x0 HTVAL=0x0 HTINST=0x0
[   53.756187] kvm [150]: SEPC=0x0 SSTATUS=0x200004120 HSTATUS=0x2002001c0
[   53.757797] kvm [150]: SCAUSE=0x14 STVAL=0x0 HTVAL=0x0 HTINST=0x0
```

solution:

add reset csr and context for riscv vcpu
qemu ioctl reset vcpu->arch.power_off state of kvm

tests:

qemu-system-riscv64 -M virt -bios none -kernel Image \
   -smp 4 -enable-kvm \
   -append "rootwait root=/dev/vda ro" \
   -drive file=rootfs.ext2,format=raw,id=hd0 \
   -device virtio-blk-device,drive=hd0

in guest shell:
reboot

qemu command:
system_reset

Signed-off-by: liguang.zhang <liguang.zhang@hexintek.com>
Signed-off-by: liguang.zhang <18622748025@163.com>
---
 target/riscv/kvm.c       | 43 ++++++++++++++++++++++++++++++++++++++++
 target/riscv/kvm_riscv.h |  1 +
 2 files changed, 44 insertions(+)

diff --git a/target/riscv/kvm.c b/target/riscv/kvm.c
index 0f932a5b96..c6a7824c9e 100644
--- a/target/riscv/kvm.c
+++ b/target/riscv/kvm.c
@@ -42,6 +42,8 @@
 #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)
 {
@@ -335,6 +337,25 @@ int kvm_arch_get_registers(CPUState *cs)
     return ret;
 }
 
+int kvm_riscv_set_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 set 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;
@@ -354,6 +375,18 @@ 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_set_mpstate_to_kvm(cpu, KVM_MP_STATE_RUNNABLE);
+        } else {
+            ret = kvm_riscv_set_mpstate_to_kvm(cpu, KVM_MP_STATE_STOPPED);
+        }
+        if (ret) {
+            return ret;
+        }
+    }
+
     return ret;
 }
 
@@ -428,6 +461,7 @@ 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;
 }
 
@@ -506,10 +540,19 @@ 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 ed281bdce0..4a4c262820 100644
--- a/target/riscv/kvm_riscv.h
+++ b/target/riscv/kvm_riscv.h
@@ -21,5 +21,6 @@
 
 void kvm_riscv_reset_vcpu(RISCVCPU *cpu);
 void kvm_riscv_set_irq(RISCVCPU *cpu, int irq, int level);
+int kvm_riscv_set_mpstate_to_kvm(RISCVCPU *cpu, int state);
 
 #endif
-- 
2.17.1