target/ppc: introduce PMUEventType and PMU overflow timers

This patch starts an IBM Power8+ compatible PMU implementation by adding
the representation of PMU events that we are going to sample,
PMUEventType. This enum represents a Perf event that is being sampled by
a specific counter 'sprn'. Events that aren't available (i.e. no event
was set in MMCR1) will be of type 'PMU_EVENT_INVALID'. Events that are
inactive due to frozen counter bits state are of type
'PMU_EVENT_INACTIVE'. Other types added in this patch are
PMU_EVENT_CYCLES and PMU_EVENT_INSTRUCTIONS.  More types will be added
later on.

Let's also add the required PMU cycle overflow timers. They will be used
to trigger cycle overflows when cycle events are being sampled. This
timer will call cpu_ppc_pmu_timer_cb(), which in turn calls
fire_PMC_interrupt().  Both functions are stubs that will be implemented
later on when EBB support is added.

Two new helper files are created to host this new logic.
cpu_ppc_pmu_init() will init all overflow timers during CPU init time.

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <20211201151734.654994-2-danielhb413@gmail.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>

hw/ppc/spapr_cpu_core.c

@@ -20,6 +20,7 @@
 #include "target/ppc/kvm_ppc.h"
 #include "hw/ppc/ppc.h"
 #include "target/ppc/mmu-hash64.h"
+#include "target/ppc/power8-pmu.h"
 #include "sysemu/numa.h"
 #include "sysemu/reset.h"
 #include "sysemu/hw_accel.h"

target/ppc/cpu.h

@@ -296,6 +296,15 @@ typedef struct ppc_v3_pate_t {
     uint64_t dw1;
 } ppc_v3_pate_t;
 
+/* PMU related structs and defines */
+#define PMU_COUNTERS_NUM 6
+typedef enum {
+    PMU_EVENT_INVALID = 0,
+    PMU_EVENT_INACTIVE,
+    PMU_EVENT_CYCLES,
+    PMU_EVENT_INSTRUCTIONS,
+} PMUEventType;
+
 /*****************************************************************************/
 /* Machine state register bits definition                                    */
 #define MSR_SF   63 /* Sixty-four-bit mode                            hflags */
@@ -1195,6 +1204,12 @@ struct CPUPPCState {
     uint32_t tm_vscr;
     uint64_t tm_dscr;
     uint64_t tm_tar;
+
+    /*
+     * Timers used to fire performance monitor alerts
+     * when counting cycles.
+     */
+    QEMUTimer *pmu_cyc_overflow_timers[PMU_COUNTERS_NUM];
 };
 
 #define SET_FIT_PERIOD(a_, b_, c_, d_)          \

target/ppc/cpu_init.c

@@ -45,6 +45,7 @@
 #include "helper_regs.h"
 #include "internal.h"
 #include "spr_tcg.h"
+#include "power8-pmu.h"
 
 /* #define PPC_DEBUG_SPR */
 /* #define USE_APPLE_GDB */
@@ -6810,6 +6811,20 @@ static void register_power9_mmu_sprs(CPUPPCState *env)
 #endif
 }
 
+/*
+ * Initialize PMU counter overflow timers for Power8 and
+ * newer Power chips when using TCG.
+ */
+static void init_tcg_pmu_power8(CPUPPCState *env)
+{
+#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
+    /* Init PMU overflow timers */
+    if (!kvm_enabled()) {
+        cpu_ppc_pmu_init(env);
+    }
+#endif
+}
+
 static void init_proc_book3s_common(CPUPPCState *env)
 {
     register_ne_601_sprs(env);
@@ -7127,6 +7142,9 @@ static void init_proc_POWER8(CPUPPCState *env)
     register_sdr1_sprs(env);
     register_book3s_207_dbg_sprs(env);
 
+    /* Common TCG PMU */
+    init_tcg_pmu_power8(env);
+
     /* POWER8 Specific Registers */
     register_book3s_ids_sprs(env);
     register_rmor_sprs(env);
@@ -7321,6 +7339,9 @@ static void init_proc_POWER9(CPUPPCState *env)
     init_proc_book3s_common(env);
     register_book3s_207_dbg_sprs(env);
 
+    /* Common TCG PMU */
+    init_tcg_pmu_power8(env);
+
     /* POWER8 Specific Registers */
     register_book3s_ids_sprs(env);
     register_amr_sprs(env);
@@ -7537,6 +7558,9 @@ static void init_proc_POWER10(CPUPPCState *env)
     init_proc_book3s_common(env);
     register_book3s_207_dbg_sprs(env);
 
+    /* Common TCG PMU */
+    init_tcg_pmu_power8(env);
+
     /* POWER8 Specific Registers */
     register_book3s_ids_sprs(env);
     register_amr_sprs(env);

target/ppc/meson.build

@@ -51,6 +51,7 @@ ppc_softmmu_ss.add(when: 'TARGET_PPC64', if_true: files(
   'mmu-book3s-v3.c',
   'mmu-hash64.c',
   'mmu-radix64.c',
+  'power8-pmu.c',
 ))
 
 target_arch += {'ppc': ppc_ss}

target/ppc/power8-pmu.c

@@ -0,0 +1,62 @@
+/*
+ * PMU emulation helpers for TCG IBM POWER chips
+ *
+ *  Copyright IBM Corp. 2021
+ *
+ * Authors:
+ *  Daniel Henrique Barboza      <danielhb413@gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#include "qemu/osdep.h"
+
+#include "power8-pmu.h"
+#include "cpu.h"
+#include "helper_regs.h"
+#include "exec/exec-all.h"
+#include "exec/helper-proto.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+#include "hw/ppc/ppc.h"
+
+#if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY)
+
+static void fire_PMC_interrupt(PowerPCCPU *cpu)
+{
+    CPUPPCState *env = &cpu->env;
+
+    if (!(env->spr[SPR_POWER_MMCR0] & MMCR0_EBE)) {
+        return;
+    }
+
+    /* PMC interrupt not implemented yet */
+    return;
+}
+
+static void cpu_ppc_pmu_timer_cb(void *opaque)
+{
+    PowerPCCPU *cpu = opaque;
+
+    fire_PMC_interrupt(cpu);
+}
+
+void cpu_ppc_pmu_init(CPUPPCState *env)
+{
+    PowerPCCPU *cpu = env_archcpu(env);
+    int i, sprn;
+
+    for (sprn = SPR_POWER_PMC1; sprn <= SPR_POWER_PMC6; sprn++) {
+        if (sprn == SPR_POWER_PMC5) {
+            continue;
+        }
+
+        i = sprn - SPR_POWER_PMC1;
+
+        env->pmu_cyc_overflow_timers[i] = timer_new_ns(QEMU_CLOCK_VIRTUAL,
+                                                       &cpu_ppc_pmu_timer_cb,
+                                                       cpu);
+    }
+}
+#endif /* defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) */

target/ppc/power8-pmu.h

@@ -0,0 +1,25 @@
+/*
+ * PMU emulation helpers for TCG IBM POWER chips
+ *
+ *  Copyright IBM Corp. 2021
+ *
+ * Authors:
+ *  Daniel Henrique Barboza      <danielhb413@gmail.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2 or later.
+ * See the COPYING file in the top-level directory.
+ */
+
+#ifndef POWER8_PMU
+#define POWER8_PMU
+
+#include "qemu/osdep.h"
+#include "cpu.h"
+#include "exec/exec-all.h"
+#include "exec/helper-proto.h"
+#include "qemu/error-report.h"
+#include "qemu/main-loop.h"
+
+void cpu_ppc_pmu_init(CPUPPCState *env);
+
+#endif