[PATCH v2 4/4] target/ppc: Implement attn instruction on BookS 64-bit processors

[Nicholas Piggin <npiggin@gmail.com>]

attn is an implementation-specific instruction that on POWER (and G5/
970) can be enabled with a HID bit (disabled = illegal), and executing
it causes the host processor to stop and the service processor to be
notified. Generally used for debugging.

Implement attn and make it checkstop the system, which should be good
enough for QEMU debugging.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
Since v1:
- New patch that also uses checkstop function. Works with skiboot.

 target/ppc/cpu.h         |  2 ++
 target/ppc/excp_helper.c | 28 ++++++++++++++++++++++++++++
 target/ppc/helper.h      |  2 ++
 target/ppc/translate.c   |  7 +++++++
 4 files changed, 39 insertions(+)

diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index 94497aa115..f6e93dec5f 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -2116,6 +2116,8 @@ void ppc_compat_add_property(Object *obj, const char *name,
 #define HID0_NAP            (1 << 22)           /* pre-2.06 */
 #define HID0_HILE           PPC_BIT(19) /* POWER8 */
 #define HID0_POWER9_HILE    PPC_BIT(4)
+#define HID0_ENABLE_ATTN    PPC_BIT(31) /* POWER8 */
+#define HID0_POWER9_ENABLE_ATTN PPC_BIT(3)
 
 /*****************************************************************************/
 /* PowerPC Instructions types definitions                                    */
diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 28d8a9b212..f46fdd2ee6 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -208,6 +208,34 @@ static void powerpc_checkstop(CPUPPCState *env, const char *reason)
 }
 
 #if defined(TARGET_PPC64)
+void helper_attn(CPUPPCState *env)
+{
+    CPUState *cs = env_cpu(env);
+    target_ulong hid0_attn = 0;
+
+    switch (env->excp_model) {
+    case POWERPC_EXCP_970:
+    case POWERPC_EXCP_POWER7:
+    case POWERPC_EXCP_POWER8:
+        hid0_attn = HID0_ENABLE_ATTN;
+        break;
+    case POWERPC_EXCP_POWER9:
+    case POWERPC_EXCP_POWER10:
+        hid0_attn = HID0_POWER9_ENABLE_ATTN;
+        break;
+    default:
+        break;
+    }
+
+    if (env->spr[SPR_HID0] & hid0_attn) {
+        powerpc_checkstop(env, "host executed attn");
+        cpu_loop_exit_noexc(cs);
+    } else {
+        raise_exception_err(env, POWERPC_EXCP_HV_EMU,
+                            POWERPC_EXCP_INVAL | POWERPC_EXCP_INVAL_INVAL);
+    }
+}
+
 static int powerpc_reset_wakeup(CPUState *cs, CPUPPCState *env, int excp,
                                 target_ulong *msr)
 {
diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index fda40b8a60..50bb105c08 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -812,3 +812,5 @@ DEF_HELPER_4(DSCLIQ, void, env, fprp, fprp, i32)
 
 DEF_HELPER_1(tbegin, void, env)
 DEF_HELPER_FLAGS_1(fixup_thrm, TCG_CALL_NO_RWG, void, env)
+
+DEF_HELPER_1(attn, void, env)
diff --git a/target/ppc/translate.c b/target/ppc/translate.c
index 372ee600b2..4e9e606d77 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -6382,6 +6382,12 @@ static void gen_dform3D(DisasContext *ctx)
 }
 
 #if defined(TARGET_PPC64)
+/* attn */
+static void gen_attn(DisasContext *ctx)
+{
+    gen_helper_attn(cpu_env);
+}
+
 /* brd */
 static void gen_brd(DisasContext *ctx)
 {
@@ -6413,6 +6419,7 @@ static void gen_brh(DisasContext *ctx)
 
 static opcode_t opcodes[] = {
 #if defined(TARGET_PPC64)
+GEN_HANDLER_E(attn, 0x00, 0x00, 0x08, 0xFFFFFDFF, PPC_NONE, PPC2_ISA207S),
 GEN_HANDLER_E(brd, 0x1F, 0x1B, 0x05, 0x0000F801, PPC_NONE, PPC2_ISA310),
 GEN_HANDLER_E(brw, 0x1F, 0x1B, 0x04, 0x0000F801, PPC_NONE, PPC2_ISA310),
 GEN_HANDLER_E(brh, 0x1F, 0x1B, 0x06, 0x0000F801, PPC_NONE, PPC2_ISA310),
-- 
2.40.1