This patch adds host satp mode while kvm/host cpu satp mode is not
set.

This patch not change the output of errno nor errno strings pattern
like other functions do. See [v3] for further information.

Change in v5:
- Adds R-B comment from Andrew Jones

Change in v4:
- Adds changelog in commit message
- Link to v3: https://lists.nongnu.org/archive/html/qemu-devel/2025-05/msg04629.html

Change in v3:
- Rebase on https://github.com/alistair23/qemu/tree/riscv-to-apply.next
  as requested
- Link to v2: https://lists.nongnu.org/archive/html/qemu-devel/2025-04/msg05203.html

Changes in v2:
- use set_satp_mode_max_supported instead of hard code
- Link to v1: https://lists.nongnu.org/archive/html/qemu-devel/2025-04/msg05094.html

Reviewed-by: Andrew Jones <ajones@ventanamicro.com>
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/2931
Signed-off-by: Meng Zhuo <mengzhuo@iscas.ac.cn>
---
 target/riscv/cpu.c         |  3 +--
 target/riscv/cpu.h         |  1 +
 target/riscv/kvm/kvm-cpu.c | 20 +++++++++++++++++++-
 3 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index d92874baa0..a84edd3a3b 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -433,8 +433,7 @@ const char *satp_mode_str(uint8_t satp_mode, bool is_32_bit)
     g_assert_not_reached();
 }
 
-static void set_satp_mode_max_supported(RISCVCPU *cpu,
-                                        uint8_t satp_mode)
+void set_satp_mode_max_supported(RISCVCPU *cpu, uint8_t satp_mode)
 {
     bool rv32 = riscv_cpu_mxl(&cpu->env) == MXL_RV32;
     const bool *valid_vm = rv32 ? valid_vm_1_10_32 : valid_vm_1_10_64;
diff --git a/target/riscv/cpu.h b/target/riscv/cpu.h
index b56d3afa69..d7136f1d72 100644
--- a/target/riscv/cpu.h
+++ b/target/riscv/cpu.h
@@ -915,6 +915,7 @@ char *riscv_cpu_get_name(RISCVCPU *cpu);
 
 void riscv_cpu_finalize_features(RISCVCPU *cpu, Error **errp);
 void riscv_add_satp_mode_properties(Object *obj);
+void set_satp_mode_max_supported(RISCVCPU *cpu, uint8_t satp_mode);
 bool riscv_cpu_accelerator_compatible(RISCVCPU *cpu);
 
 /* CSR function table */
diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c
index 82f9728636..18fbca1a08 100644
--- a/target/riscv/kvm/kvm-cpu.c
+++ b/target/riscv/kvm/kvm-cpu.c
@@ -999,6 +999,23 @@ static void kvm_riscv_destroy_scratch_vcpu(KVMScratchCPU *scratch)
     close(scratch->kvmfd);
 }
 
+static void kvm_riscv_init_satp_mode(RISCVCPU *cpu, KVMScratchCPU *kvmcpu)
+{
+    CPURISCVState *env = &cpu->env;
+    struct kvm_one_reg reg;
+    int ret;
+    uint64_t val;
+
+    reg.id = RISCV_CONFIG_REG(env, satp_mode);
+    reg.addr = (uint64_t)&val;
+    ret = ioctl(kvmcpu->cpufd, KVM_GET_ONE_REG, &reg);
+    if (ret != 0) {
+        error_report("Unable to retrieve satp from host, error %d", ret);
+    }
+
+    set_satp_mode_max_supported(cpu, val);
+}
+
 static void kvm_riscv_init_machine_ids(RISCVCPU *cpu, KVMScratchCPU *kvmcpu)
 {
     struct kvm_one_reg reg;
@@ -1302,6 +1319,7 @@ static void riscv_init_kvm_registers(Object *cpu_obj)
     kvm_riscv_init_machine_ids(cpu, &kvmcpu);
     kvm_riscv_init_misa_ext_mask(cpu, &kvmcpu);
     kvm_riscv_init_cfg(cpu, &kvmcpu);
+    kvm_riscv_init_satp_mode(cpu, &kvmcpu);
 
     kvm_riscv_destroy_scratch_vcpu(&kvmcpu);
 }
@@ -1980,7 +1998,7 @@ static bool kvm_cpu_realize(CPUState *cs, Error **errp)
         }
     }
 
-   return true;
+    return true;
 }
 
 void riscv_kvm_cpu_finalize_features(RISCVCPU *cpu, Error **errp)
-- 
2.39.5