Re: [PATCH 3/3] target/riscv: Add SBI STA state to vmstate

[Daniel Henrique Barboza]

Hi,

On 10/17/2026 11:51 AM, Wang Yechao wrote:

Save and restore the KVM SBI state as a vmstate subsection, so that
a guest using SBI STA keeps working after live migration. Only the
STA shmem address (shmem_lo and shmem_hi) is saved for now; other
SBI state can be appended to kvm_sbi_state as it is added.

Signed-off-by: Wang Yechao <wang.yechao...@zte.com.cn>
---
  target/riscv/machine.c | 18 ++++++++++++++++++
  1 file changed, 18 insertions(+)

diff --git a/target/riscv/machine.c b/target/riscv/machine.c
index 0de06e9588..b8cdca79cc 100644
--- a/target/riscv/machine.c
+++ b/target/riscv/machine.c
@@ -318,6 +318,23 @@ static const VMStateDescription vmstate_kvm_mp_state = {
          VMSTATE_END_OF_LIST()
      }
  };
+
+static bool kvm_sbi_state_needed(void *opaque)
+{
+    return kvm_enabled();
+}

I think kvm_enabled() isn't enough here since there's no guarantee that
the current running kvm driver supports SBI STA.

If we take the existing mp_state as an example, in kvm-cpu.c we have:

bool kvm_riscv_has_mp_state(void)
{
    return cap_has_mp_state;
}

And then, in machine.c:

static bool kvm_mp_state_needed(void *opaque)
{
    return kvm_enabled() && kvm_riscv_has_mp_state();
}


I think we can do the same here.  In patch 1 you're setting 
kvm_sbi_sta.supported
to true if SBI STA is available.  We can add a:

bool kvm_riscv_has_sbi_sta_state(void)
{
    return kvm_sbi_sta.supported;
}

And then you can use it as another check in kvm_sbi_state_needed() too.


Thanks,
Daniel

+
+static const VMStateDescription vmstate_kvm_sbi_state = {
+    .name = "cpu/kvm-sbi-state",
+    .version_id = 1,
+    .minimum_version_id = 1,
+    .needed = kvm_sbi_state_needed,
+    .fields = (const VMStateField[]) {
+        VMSTATE_UINT64(env.kvm_sbi_sta.shmem_lo, RISCVCPU),
+        VMSTATE_UINT64(env.kvm_sbi_sta.shmem_hi, RISCVCPU),
+        VMSTATE_END_OF_LIST()
+    }
+};
  #endif

static bool debug_needed(void *opaque)

@@ -645,6 +662,7 @@ const VMStateDescription vmstate_riscv_cpu = {
          &vmstate_kvm_timer_frequency,
          &vmstate_kvmtimer,
          &vmstate_kvm_mp_state,
+        &vmstate_kvm_sbi_state,
  #endif
          &vmstate_envcfg,
          &vmstate_debug,