Re: [PATCH 2/3] target/riscv/kvm: Sync SBI STA shmem registers with KVM

[Daniel Henrique Barboza]

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

Now that SBI STA support is detected, synchronize the shared memory
address (shmem_lo and shmem_hi) between KVM and QEMU using the
KVM_REG_RISCV_SBI_STA one-reg interface.

The shmem address is configured by the guest, so QEMU does not
need to perform put reg operations during reset.

Signed-off-by: Wang Yechao <wang.yechao...@zte.com.cn>
---

Reviewed-by: Daniel Henrique Barboza <daniel.barb...@oss.qualcomm.com>

  target/riscv/cpu.h         |  6 +++
  target/riscv/kvm/kvm-cpu.c | 97 ++++++++++++++++++++++++++++++++++++++
  2 files changed, 103 insertions(+)

diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index b65d631994..4da7963d3d 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -34,6 +34,9 @@
  #include "cpu_cfg.h"
  #include "qapi/qapi-types-common.h"
  #include "cpu-qom.h"
+#ifdef CONFIG_KVM
+#include <linux/kvm.h>
+#endif

typedef struct CPUArchState CPURISCVState; @@ -550,6 +553,9 @@ struct CPUArchState {

      /* KVM multiprocessor state */
      uint32_t kvm_mp_state;
      bool kvm_mp_state_loaded;
+
+    /* kvm sbi state */
+    struct kvm_riscv_sbi_sta kvm_sbi_sta;
  #endif /* CONFIG_KVM */
  };

diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c

index 8ab43432dd..ba5ba63854 100644
--- a/target/riscv/kvm/kvm-cpu.c
+++ b/target/riscv/kvm/kvm-cpu.c
@@ -123,6 +123,11 @@ static uint64_t kvm_riscv_vector_reg_id(RISCVCPU *cpu,
      KVM_RISCV_REG_ID_ULONG(KVM_REG_RISCV_VECTOR, \
                             KVM_REG_RISCV_VECTOR_CSR_REG(name))

+#define RISCV_SBI_STA_REG(name) \

+    KVM_RISCV_REG_ID_ULONG(KVM_REG_RISCV_SBI_STATE, \
+                           KVM_REG_RISCV_SBI_STA | \
+                           KVM_REG_RISCV_SBI_STA_REG(name))
+
  #define KVM_RISCV_GET_TIMER(cs, name, reg) \
      do { \
          int ret = kvm_get_one_reg(cs, RISCV_TIMER_REG(name), &reg); \
@@ -1010,6 +1015,88 @@ static int kvm_riscv_put_regs_vector(CPUState *cs)
      return ret;
  }

+static int kvm_riscv_get_regs_sbi_sta(CPUState *cs)

+{
+    RISCVCPU *cpu = RISCV_CPU(cs);
+    CPURISCVState *env = &cpu->env;
+    target_ulong reg;
+    int ret = 0;
+
+    if (!kvm_sbi_sta.supported) {
+        return 0;
+    }
+
+    ret = kvm_get_one_reg(cs, RISCV_SBI_STA_REG(shmem_lo), &reg);
+    if (ret) {
+        return ret;
+    }
+    env->kvm_sbi_sta.shmem_lo = reg;
+
+    ret = kvm_get_one_reg(cs, RISCV_SBI_STA_REG(shmem_hi), &reg);
+    if (ret) {
+        return ret;
+    }
+    env->kvm_sbi_sta.shmem_hi = reg;
+
+    return ret;
+}
+
+static int kvm_riscv_get_regs_sbi_state(CPUState *cs)
+{
+    int ret = 0;
+
+    ret = kvm_riscv_get_regs_sbi_sta(cs);
+    if (ret) {
+        return ret;
+    }
+
+    return 0;
+}
+
+static int kvm_riscv_put_regs_sbi_sta(CPUState *cs)
+{
+    RISCVCPU *cpu = RISCV_CPU(cs);
+    CPURISCVState *env = &cpu->env;
+    target_ulong reg;
+    int ret = 0;
+
+    if (!kvm_sbi_sta.supported) {
+        return 0;
+    }
+
+    reg = env->kvm_sbi_sta.shmem_lo;
+    ret = kvm_set_one_reg(cs, RISCV_SBI_STA_REG(shmem_lo), &reg);
+    if (ret) {
+        return ret;
+    }
+
+    reg = env->kvm_sbi_sta.shmem_hi;
+    ret = kvm_set_one_reg(cs, RISCV_SBI_STA_REG(shmem_hi), &reg);
+    if (ret) {
+        return ret;
+    }
+
+    return ret;
+}
+
+static int kvm_riscv_put_regs_sbi_state(CPUState *cs, KvmPutState level)
+{
+    int ret = 0;
+
+    /*
+     * The shmem address of SBI STA is configured by the guest. During reset,
+     * QEMU does not need to perform put reg operations.
+     */
+    if (level != KVM_PUT_RESET_STATE) {
+        ret = kvm_riscv_put_regs_sbi_sta(cs);
+        if (ret) {
+            return ret;
+        }
+    }
+
+    return ret;
+}
+
  typedef struct KVMScratchCPU {
      int kvmfd;
      int vmfd;
@@ -1433,6 +1520,11 @@ int kvm_arch_get_registers(CPUState *cs, Error **errp)
          return ret;
      }

+ ret = kvm_riscv_get_regs_sbi_state(cs);

+    if (ret) {
+        return ret;
+    }
+
      if (cap_has_mp_state) {
          struct kvm_mp_state mp_state;

@@ -1520,6 +1612,11 @@ int kvm_arch_put_registers(CPUState *cs, KvmPutState level, Error **errp)

          return ret;
      }

+ ret = kvm_riscv_put_regs_sbi_state(cs, level);

+    if (ret) {
+        return ret;
+    }
+
      if (KVM_PUT_RESET_STATE == level) {
          CPURISCVState *env = &RISCV_CPU(cs)->env;