[MIPS] Add Goldfish target support

Basic Goldfish support for MIPS.

Also, Fix host CPU consumption when guest is idle

When the CPU is in wait state, do not wake-up if an interrupt can't be
taken. This avoid host CPU running at 100% if a device (e.g. timer) has
an interrupt line left enabled.

Also factorize code to check if interrupts are enabled in
cpu_mips_hw_interrupts_pending().

CPU consumption based on a patch from
Edgar E. Iglesias <edgar.iglesias@gmail.com>

Change-Id: Ie8371c8d0c9af1e0c8ba4cac419979350de0f5d9
Signed-off-by: yajin <yajin@mips.com.cm>
Signed-off-by: Douglas Leung <douglas@mips.com>
Signed-off-by: Bhanu Chetlapalli <bhanu@mips.com>
Signed-off-by: Chris Dearman <chris@mips.com>

2 files changed, 46 insertions, 3 deletions

diff --git a/target-mips/cpu.h b/target-mips/cpu.h
index 27bdc95..7c04fbe 100644
--- a/target-mips/cpu.h
+++ b/target-mips/cpu.h
@@ -518,6 +518,37 @@ static inline void cpu_clone_regs(CPUState *env, target_ulong newsp)
     env->active_tc.gpr[2] = 0;
 }
 
+static inline int cpu_mips_hw_interrupts_pending(CPUState *env)
+{
+    int32_t pending;
+    int32_t status;
+    int r;
+
+    if (!(env->CP0_Status & (1 << CP0St_IE)) ||
+        (env->CP0_Status & (1 << CP0St_EXL)) ||
+        (env->CP0_Status & (1 << CP0St_ERL)) ||
+        (env->hflags & MIPS_HFLAG_DM)) {
+        /* Interrupts are disabled */
+        return 0;
+    }
+
+    pending = env->CP0_Cause & CP0Ca_IP_mask;
+    status = env->CP0_Status & CP0Ca_IP_mask;
+
+    if (env->CP0_Config3 & (1 << CP0C3_VEIC)) {
+        /* A MIPS configured with a vectorizing external interrupt controller
+           will feed a vector into the Cause pending lines. The core treats
+           the status lines as a vector level, not as indiviual masks.  */
+        r = pending > status;
+    } else {
+        /* A MIPS configured with compatibility or VInt (Vectored Interrupts)
+           treats the pending lines as individual interrupt lines, the status
+           lines are individual masks.  */
+        r = pending & status;
+    }
+    return r;
+}
+
 #include "cpu-all.h"
 #include "exec-all.h"
 
diff --git a/target-mips/exec.h b/target-mips/exec.h
index 8a118bb..0720366 100644
--- a/target-mips/exec.h
+++ b/target-mips/exec.h
@@ -35,10 +35,22 @@ static inline void regs_to_env(void)
 
 static inline int cpu_has_work(CPUState *env)
 {
-    return (env->interrupt_request &
-            (CPU_INTERRUPT_HARD | CPU_INTERRUPT_TIMER));
-}
+    int has_work = 0;
+
+    /* It is implementation dependent if non-enabled interrupts
+       wake-up the CPU, however most of the implementations only
+       check for interrupts that can be taken. */
+    if ((env->interrupt_request & CPU_INTERRUPT_HARD) &&
+        cpu_mips_hw_interrupts_pending(env)) {
+        has_work = 1;
+    }
 
+    if (env->interrupt_request & CPU_INTERRUPT_TIMER) {
+        has_work = 1;
+    }
+
+    return has_work;
+}
 
 static inline int cpu_halted(CPUState *env)
 {