target-alpha: Add high-resolution access to wall clock and an alarm.

The alarm is a fully general one-shot time comparator, which will be
usable under Linux as a hrtimer source.  It's much more flexible than
the RTC source available on real hardware.

The wall clock allows the guest access to the host timekeeping.  Much
like the KVM wall clock source for other guests.

Both are accessed via the PALcode Cserve entry point.

Signed-off-by: Richard Henderson <rth@twiddle.net>

4 files changed, 48 insertions, 4 deletions

diff --git a/target-alpha/cpu.h b/target-alpha/cpu.h
index c2e7bb3..9d61d45 100644
--- a/target-alpha/cpu.h
+++ b/target-alpha/cpu.h
@@ -265,6 +265,10 @@ struct CPUAlphaState {
     uint64_t scratch[24];
 #endif
 
+    /* This alarm doesn't exist in real hardware; we wish it did.  */
+    struct QEMUTimer *alarm_timer;
+    uint64_t alarm_expire;
+
 #if TARGET_LONG_BITS > HOST_LONG_BITS
     /* temporary fixed-point registers
      * used to emulate 64 bits target on 32 bits hosts
diff --git a/target-alpha/helper.h b/target-alpha/helper.h
index c352c24..b693cee 100644
--- a/target-alpha/helper.h
+++ b/target-alpha/helper.h
@@ -113,7 +113,11 @@ DEF_HELPER_2(stq_c_phys, i64, i64, i64)
 
 DEF_HELPER_FLAGS_0(tbia, TCG_CALL_CONST, void)
 DEF_HELPER_FLAGS_1(tbis, TCG_CALL_CONST, void, i64)
+
 DEF_HELPER_1(halt, void, i64);
+
+DEF_HELPER_FLAGS_0(get_time, TCG_CALL_CONST, i64)
+DEF_HELPER_FLAGS_1(set_alarm, TCG_CALL_CONST, void, i64)
 #endif
 
 #include "def-helper.h"
diff --git a/target-alpha/op_helper.c b/target-alpha/op_helper.c
index 1896ab8..cc102db 100644
--- a/target-alpha/op_helper.c
+++ b/target-alpha/op_helper.c
@@ -1228,6 +1228,21 @@ void helper_halt(uint64_t restart)
         qemu_system_shutdown_request();
     }
 }
+
+uint64_t helper_get_time(void)
+{
+    return qemu_get_clock_ns(rtc_clock);
+}
+
+void helper_set_alarm(uint64_t expire)
+{
+    if (expire) {
+        env->alarm_expire = expire;
+        qemu_mod_timer(env->alarm_timer, expire);
+    } else {
+        qemu_del_timer(env->alarm_timer);
+    }
+}
 #endif
 
 /*****************************************************************************/
diff --git a/target-alpha/translate.c b/target-alpha/translate.c
index 0acbd68..a961159 100644
--- a/target-alpha/translate.c
+++ b/target-alpha/translate.c
@@ -1590,18 +1590,34 @@ static int cpu_pr_data(int pr)
         return offsetof(CPUAlphaState, shadow[pr - 32]);
     case 40 ... 63:
         return offsetof(CPUAlphaState, scratch[pr - 40]);
+
+    case 251:
+        return offsetof(CPUAlphaState, alarm_expire);
     }
     return 0;
 }
 
-static void gen_mfpr(int ra, int regno)
+static ExitStatus gen_mfpr(int ra, int regno)
 {
     int data = cpu_pr_data(regno);
 
     /* In our emulated PALcode, these processor registers have no
        side effects from reading.  */
     if (ra == 31) {
-        return;
+        return NO_EXIT;
+    }
+
+    if (regno == 250) {
+        /* WALL_TIME */
+        if (use_icount) {
+            gen_io_start();
+            gen_helper_get_time(cpu_ir[ra]);
+            gen_io_end();
+            return EXIT_PC_STALE;
+        } else {
+            gen_helper_get_time(cpu_ir[ra]);
+            return NO_EXIT;
+        }
     }
 
     /* The basic registers are data only, and unknown registers
@@ -1615,6 +1631,7 @@ static void gen_mfpr(int ra, int regno)
     } else {
         tcg_gen_ld_i64(cpu_ir[ra], cpu_env, data);
     }
+    return NO_EXIT;
 }
 
 static ExitStatus gen_mtpr(DisasContext *ctx, int rb, int regno)
@@ -1650,6 +1667,11 @@ static ExitStatus gen_mtpr(DisasContext *ctx, int rb, int regno)
         gen_helper_halt(tmp);
         return EXIT_PC_STALE;
 
+    case 251:
+        /* ALARM */
+        gen_helper_set_alarm(tmp);
+        break;
+
     default:
         /* The basic registers are data only, and unknown registers
            are read-zero, write-ignore.  */
@@ -2772,8 +2794,7 @@ static ExitStatus translate_one(DisasContext *ctx, uint32_t insn)
         /* HW_MFPR (PALcode) */
 #ifndef CONFIG_USER_ONLY
         if (ctx->tb->flags & TB_FLAGS_PAL_MODE) {
-            gen_mfpr(ra, insn & 0xffff);
-            break;
+            return gen_mfpr(ra, insn & 0xffff);
         }
 #endif
         goto invalid_opc;