ppc: Initial HDEC support

The current behaviour isn't completely right, as for the DEC, we
don't properly re-arm when wrapping around, but I will fix this
in a separate patch.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
[clg: fixed checkpatch.pl errors ]
Signed-off-by: Cédric Le Goater <clg@kaod.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

hw/ppc/ppc.c

@@ -699,9 +699,18 @@ static inline void cpu_ppc_decr_lower(PowerPCCPU *cpu)
 
 static inline void cpu_ppc_hdecr_excp(PowerPCCPU *cpu)
 {
+    CPUPPCState *env = &cpu->env;
+
     /* Raise it */
-    LOG_TB("raise decrementer exception\n");
-    ppc_set_irq(cpu, PPC_INTERRUPT_HDECR, 1);
+    LOG_TB("raise hv decrementer exception\n");
+
+    /* The architecture specifies that we don't deliver HDEC
+     * interrupts in a PM state. Not only they don't cause a
+     * wakeup but they also get effectively discarded.
+     */
+    if (!env->in_pm_state) {
+        ppc_set_irq(cpu, PPC_INTERRUPT_HDECR, 1);
+    }
 }
 
 static inline void cpu_ppc_hdecr_lower(PowerPCCPU *cpu)
@@ -928,9 +937,7 @@ clk_setup_cb cpu_ppc_tb_init (CPUPPCState *env, uint32_t freq)
     }
     /* Create new timer */
     tb_env->decr_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, &cpu_ppc_decr_cb, cpu);
-    if (0) {
-        /* XXX: find a suitable condition to enable the hypervisor decrementer
-         */
+    if (env->has_hv_mode) {
         tb_env->hdecr_timer = timer_new_ns(QEMU_CLOCK_VIRTUAL, &cpu_ppc_hdecr_cb,
                                                 cpu);
     } else {

target-ppc/excp_helper.c

@@ -753,7 +753,6 @@ void ppc_cpu_do_interrupt(CPUState *cs)
 static void ppc_hw_interrupt(CPUPPCState *env)
 {
     PowerPCCPU *cpu = ppc_env_get_cpu(env);
-    int hdice;
 #if 0
     CPUState *cs = CPU(cpu);
 
@@ -781,15 +780,13 @@ static void ppc_hw_interrupt(CPUPPCState *env)
         return;
     }
 #endif
-    if (0) {
-        /* XXX: find a suitable condition to enable the hypervisor mode */
-        hdice = env->spr[SPR_LPCR] & 1;
-    } else {
-        hdice = 0;
-    }
-    if ((msr_ee != 0 || msr_hv == 0 || msr_pr != 0) && hdice != 0) {
-        /* Hypervisor decrementer exception */
-        if (env->pending_interrupts & (1 << PPC_INTERRUPT_HDECR)) {
+    /* Hypervisor decrementer exception */
+    if (env->pending_interrupts & (1 << PPC_INTERRUPT_HDECR)) {
+        /* LPCR will be clear when not supported so this will work */
+        bool hdice = !!(env->spr[SPR_LPCR] & LPCR_HDICE);
+        if ((msr_ee != 0 || msr_hv == 0) && hdice) {
+            /* HDEC clears on delivery */
+            env->pending_interrupts &= ~(1 << PPC_INTERRUPT_HDECR);
             powerpc_excp(cpu, env->excp_model, POWERPC_EXCP_HDECR);
             return;
         }
@@ -941,6 +938,11 @@ void helper_pminsn(CPUPPCState *env, powerpc_pm_insn_t insn)
     cs->halted = 1;
     env->in_pm_state = true;
 
+    /* The architecture specifies that HDEC interrupts are
+     * discarded in PM states
+     */
+    env->pending_interrupts &= ~(1 << PPC_INTERRUPT_HDECR);
+
     /* Technically, nap doesn't set EE, but if we don't set it
      * then ppc_hw_interrupt() won't deliver. We could add some
      * other tests there based on LPCR but it's simpler to just

target-ppc/helper.h

@@ -600,6 +600,8 @@ DEF_HELPER_2(store_601_rtcl, void, env, tl)
 DEF_HELPER_2(store_601_rtcu, void, env, tl)
 DEF_HELPER_1(load_decr, tl, env)
 DEF_HELPER_2(store_decr, void, env, tl)
+DEF_HELPER_1(load_hdecr, tl, env)
+DEF_HELPER_2(store_hdecr, void, env, tl)
 DEF_HELPER_2(store_hid0_601, void, env, tl)
 DEF_HELPER_3(store_403_pbr, void, env, i32, tl)
 DEF_HELPER_1(load_40x_pit, tl, env)

target-ppc/timebase_helper.c

@@ -102,6 +102,16 @@ void helper_store_decr(CPUPPCState *env, target_ulong val)
     cpu_ppc_store_decr(env, val);
 }
 
+target_ulong helper_load_hdecr(CPUPPCState *env)
+{
+    return cpu_ppc_load_hdecr(env);
+}
+
+void helper_store_hdecr(CPUPPCState *env, target_ulong val)
+{
+    cpu_ppc_store_hdecr(env, val);
+}
+
 target_ulong helper_load_40x_pit(CPUPPCState *env)
 {
     return load_40x_pit(env);

target-ppc/translate_init.c

@@ -277,6 +277,32 @@ static void spr_read_purr (DisasContext *ctx, int gprn, int sprn)
 {
     gen_helper_load_purr(cpu_gpr[gprn], cpu_env);
 }
+
+/* HDECR */
+static void spr_read_hdecr(DisasContext *ctx, int gprn, int sprn)
+{
+    if (ctx->tb->cflags & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
+    gen_helper_load_hdecr(cpu_gpr[gprn], cpu_env);
+    if (ctx->tb->cflags & CF_USE_ICOUNT) {
+        gen_io_end();
+        gen_stop_exception(ctx);
+    }
+}
+
+static void spr_write_hdecr(DisasContext *ctx, int sprn, int gprn)
+{
+    if (ctx->tb->cflags & CF_USE_ICOUNT) {
+        gen_io_start();
+    }
+    gen_helper_store_hdecr(cpu_env, cpu_gpr[gprn]);
+    if (ctx->tb->cflags & CF_USE_ICOUNT) {
+        gen_io_end();
+        gen_stop_exception(ctx);
+    }
+}
+
 #endif
 #endif
 
@@ -7824,6 +7850,10 @@ static void gen_spr_power5p_lpar(CPUPPCState *env)
                      SPR_NOACCESS, SPR_NOACCESS,
                      &spr_read_generic, &spr_write_lpcr,
                      KVM_REG_PPC_LPCR, LPCR_LPES0 | LPCR_LPES1);
+    spr_register_hv(env, SPR_HDEC, "HDEC",
+                    SPR_NOACCESS, SPR_NOACCESS,
+                    SPR_NOACCESS, SPR_NOACCESS,
+                    &spr_read_hdecr, &spr_write_hdecr, 0);
 #endif
 }