Le 03/09/2026 à 06:45, 54weasels a écrit :
Why this change is made & How it will be used:
The Sun-3 ROM expects the Cache Control Register (CAAR) to exist on the 68020.
Reading/writing this register currently aborts QEMU. This patch provides a
dummy implementation that simply ignores writes and returns 0 on reads,
allowing the ROM to continue booting.
Impact on existing functionality:
No impact on existing targets. ColdFire and Mac targets do not access CAAR in a
way that currently aborts, and providing a safe dummy implementation ensures
robustness across M68k boards.
Signed-off-by: 54weasels <[email protected]>
---
target/m68k/helper.c | 8 ++++++--
1 file changed, 6 insertions(+), 2 deletions(-)
diff --git a/target/m68k/helper.c b/target/m68k/helper.c
index 5f91d206f5..68f523ea84 100644
--- a/target/m68k/helper.c
+++ b/target/m68k/helper.c
@@ -281,8 +281,10 @@ void HELPER(m68k_movec_to)(CPUM68KState *env, uint32_t
reg, uint32_t val)
return;
}
break;
- /* Unimplemented Registers */
+ /* Dummy implementation for CAAR */
case M68K_CR_CAAR:
CAAR is only supported on 020 and 030, use m68k_feature() here to check them and return. Otherwise
use break to go to raise_exception_ra()
+ return;
+ /* Unimplemented Registers */
case M68K_CR_PCR:
case M68K_CR_BUSCR:
cpu_abort(env_cpu(env),
@@ -385,8 +387,10 @@ uint32_t HELPER(m68k_movec_from)(CPUM68KState *env,
uint32_t reg)
return env->mmu.ttr[M68K_DTTR1];
}
break;
- /* Unimplemented Registers */
+ /* Dummy implementation for CAAR */
case M68K_CR_CAAR:
+ return 0;
Same comment as for m68k_movec_to()
+ /* Unimplemented Registers */
case M68K_CR_PCR:
case M68K_CR_BUSCR:
cpu_abort(env_cpu(env), "Unimplemented control register read 0x%x\n",
Thanks,
Laurent
