target/riscv/kvm: Add SBI STA register sync and migration support

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 <[email protected]>

---

  target/riscv/kvm/kvm-cpu.c   |  5 +++++
  target/riscv/kvm/kvm_riscv.h |  1 +
  target/riscv/machine.c       | 18 ++++++++++++++++++
  3 files changed, 24 insertions(+)

target/riscv/kvm/kvm-cpu.c +5 -0

index ba5ba63854..0586e290dd 100644
@@ -1015,6 +1015,11 @@ static int kvm_riscv_put_regs_vector(CPUState *cs)
      return ret;
  }
 
+bool kvm_riscv_has_sbi_sta_state(void)
+{
+     return kvm_sbi_sta.supported;
+}
+
  static int kvm_riscv_get_regs_sbi_sta(CPUState *cs)
  {
      RISCVCPU *cpu = RISCV_CPU(cs);

target/riscv/kvm/kvm_riscv.h +1 -0

index aef681f0a2..5e17bacad1 100644
@@ -35,6 +35,7 @@ void kvm_riscv_aia_create(MachineState *machine, uint64_t group_shift,
                            uint64_t guest_num);
  void riscv_kvm_aplic_request(void *opaque, int irq, int level);
  bool kvm_riscv_has_mp_state(void);
+bool kvm_riscv_has_sbi_sta_state(void);
  int kvm_riscv_check_timer_frequency(RISCVCPU *cpu);
  void riscv_kvm_cpu_finalize_features(RISCVCPU *cpu, Error **errp);
  uint64_t kvm_riscv_get_timebase_frequency(RISCVCPU *cpu);

target/riscv/machine.c +18 -0

index 0de06e9588..9fc699a482 100644
@@ -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() && kvm_riscv_has_sbi_sta_state();
+}
+
+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,

KVM already exposes the SBI STA extension and its shmem address through
the one-reg interface, but QEMU does not consume it. As a result, the guest-configured shmem address is not kept in sync between KVM and QEMU,
and is lost on migration, breaking STA for the guest after live migration.

This series probes for SBI STA support via get-reg-list, synchronizes the shmem address (shmem_lo/shmem_hi) between KVM and QEMU (skipping the
put at reset, since the address is configured by the guest), and saves
the address in vmstate so STA keeps working after live migration. Only
the STA shmem address is saved for now; other SBI state can be appended
to kvm_sbi_state later.

Changes in v2:
 - patch03, only save the sbi sta state if kvm sbi sta supported.
 - rebase on riscv-to-apply.next.

 - Link to v1:

https://lore.kernel.org/qemu-devel/[email protected]
/

Wang Yechao (3):
  target/riscv/kvm: Detect SBI STA extension support target/riscv/kvm: Sync SBI STA shmem registers with KVM target/riscv: Add SBI STA state to vmstate

 target/riscv/cpu.h           |   6 ++
 target/riscv/kvm/kvm-cpu.c   | 122
+++++++++++++++++++++++++++++++++++
 target/riscv/kvm/kvm_riscv.h |   1 +
 target/riscv/machine.c       |  18 ++++++

 4 files changed, 147 insertions(+)

KVM already exposes the SBI STA extension and its shmem address through
the one-reg interface, but QEMU does not consume it. As a result, the guest-configured shmem address is not kept in sync between KVM and QEMU,
and is lost on migration, breaking STA for the guest after live migration.

This series probes for SBI STA support via get-reg-list, synchronizes the shmem address (shmem_lo/shmem_hi) between KVM and QEMU (skipping the
put at reset, since the address is configured by the guest), and saves
the address in vmstate so STA keeps working after live migration. Only
the STA shmem address is saved for now; other SBI state can be appended
to kvm_sbi_state later.

Changes in v2:
 - patch03, only save the sbi sta state if kvm sbi sta supported.
 - rebase on riscv-to-apply.next.

 - Link to v1:

https://lore.kernel.org/qemu-devel/[email protected]
/

Wang Yechao (3):
  target/riscv/kvm: Detect SBI STA extension support target/riscv/kvm: Sync SBI STA shmem registers with KVM target/riscv: Add SBI STA state to vmstate

 target/riscv/cpu.h           |   6 ++
 target/riscv/kvm/kvm-cpu.c   | 122
+++++++++++++++++++++++++++++++++++
 target/riscv/kvm/kvm_riscv.h |   1 +
 target/riscv/machine.c       |  18 ++++++

 4 files changed, 147 insertions(+)