[PATCH] riscv: disable Smdbltrp for the max cpu

[Clément Léger]

When present, Smdbltrp is enabled by default and MDT needs to be cleared
to avoid generating a double trap. Since not all firmwares are currently
ready to handle that, disable it for the max cpu.

Reported-by: Atish Patra <atishp@rivosinc.com>
Signed-off-by: Clément Léger <cleger@rivosinc.com>

---
 target/riscv/tcg/tcg-cpu.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/target/riscv/tcg/tcg-cpu.c b/target/riscv/tcg/tcg-cpu.c
index 48be24bbbe..0a137281de 100644
--- a/target/riscv/tcg/tcg-cpu.c
+++ b/target/riscv/tcg/tcg-cpu.c
@@ -1439,6 +1439,16 @@ static void riscv_init_max_cpu_extensions(Object *obj)
         isa_ext_update_enabled(cpu, CPU_CFG_OFFSET(ext_smrnmi), false);
         qemu_log("Smrnmi is disabled in the 'max' type CPU\n");
     }
+
+    /*
+     * ext_smdbltrp requires the firmware to clear MSTATUS.MDT on startup to
+     * avoid generating a double trap. OpenSBI does not currently support it,
+     * disable it for now.
+     */
+    if (cpu->cfg.ext_smdbltrp) {
+        isa_ext_update_enabled(cpu, CPU_CFG_OFFSET(ext_smdbltrp), false);
+        qemu_log("Smdbltrp is disabled in the 'max' type CPU\n");
+    }
 }
 
 static bool riscv_cpu_has_max_extensions(Object *cpu_obj)
-- 
2.47.1