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>

1 files changed, 25 insertions, 4 deletions

diff --git a/target-alpha/translate.c b/target-alpha/translate.c
index 0acbd682d3..a961159d5d 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;