Re: [RFC PATCH 4/5] target/ppc: Add msgsnd/p and DPDES SMT support

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Re: [RFC PATCH 4/5] target/ppc: Add msgsnd/p and DPDES SMT support

From:	Cédric Le Goater
Subject:	Re: [RFC PATCH 4/5] target/ppc: Add msgsnd/p and DPDES SMT support
Date:	Thu, 1 Jun 2023 09:13:17 +0200
User-agent:	Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.10.0

On 5/31/23 03:23, Nicholas Piggin wrote:

Doorbells in SMT need to coordinate msgsnd/msgclr and DPDES access from
multiple threads that affect the same state.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
  hw/ppc/ppc.c                                  |  6 ++
  include/hw/ppc/ppc.h                          |  1 +
  target/ppc/cpu.h                              |  7 +-
  target/ppc/excp_helper.c                      | 86 +++++++++++++------
  target/ppc/gdbstub.c                          |  2 +-
  target/ppc/helper.h                           |  2 +-
  target/ppc/misc_helper.c                      | 60 +++++++++++--
  target/ppc/translate.c                        |  8 ++
  .../ppc/translate/processor-ctrl-impl.c.inc   |  2 +-
  9 files changed, 140 insertions(+), 34 deletions(-)

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index 80b4706db2..e30853413b 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -1434,6 +1434,12 @@ int ppc_cpu_pir(PowerPCCPU *cpu)
      return env->spr_cb[SPR_PIR].default_value;
  }

+int ppc_cpu_tir(PowerPCCPU *cpu)

+{
+    CPUPPCState *env = &cpu->env;
+    return env->spr_cb[SPR_PIR].default_value;


PIR or TIR ?

+}
+
  PowerPCCPU *ppc_get_vcpu_by_pir(int pir)
  {
      CPUState *cs;
diff --git a/include/hw/ppc/ppc.h b/include/hw/ppc/ppc.h
index 02af03ada2..e095c002dc 100644
--- a/include/hw/ppc/ppc.h
+++ b/include/hw/ppc/ppc.h
@@ -6,6 +6,7 @@
  void ppc_set_irq(PowerPCCPU *cpu, int n_IRQ, int level);
  PowerPCCPU *ppc_get_vcpu_by_pir(int pir);
  int ppc_cpu_pir(PowerPCCPU *cpu);
+int ppc_cpu_tir(PowerPCCPU *cpu);

/* PowerPC hardware exceptions management helpers */

  typedef void (*clk_setup_cb)(void *opaque, uint32_t freq);
diff --git a/target/ppc/cpu.h b/target/ppc/cpu.h
index b594408a8d..b04b309c71 100644
--- a/target/ppc/cpu.h
+++ b/target/ppc/cpu.h
@@ -1056,7 +1056,12 @@ FIELD(FPSCR, FI, FPSCR_FI, 1)

#define DBELL_TYPE_DBELL_SERVER (0x05 << DBELL_TYPE_SHIFT)-#define DBELL_BRDCAST PPC_BIT(37)

+/* XXX: make sure this does not break BookE */
+#define DBELL_BRDCAST_MASK             PPC_BITMASK(37, 38)
+#define DBELL_BRDCAST_SHIFT            25
+#define DBELL_BRDCAST_SUBPROC          (0x1 << DBELL_BRDCAST_SHIFT)
+#define DBELL_BRDCAST_CORE             (0x2 << DBELL_BRDCAST_SHIFT)
+
  #define DBELL_LPIDTAG_SHIFT            14
  #define DBELL_LPIDTAG_MASK             (0xfff << DBELL_LPIDTAG_SHIFT)
  #define DBELL_PIRTAG_MASK              0x3fff
diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 4925996cf3..5fc2e17269 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -3085,7 +3085,7 @@ void helper_msgsnd(target_ulong rb)
          PowerPCCPU *cpu = POWERPC_CPU(cs);
          CPUPPCState *cenv = &cpu->env;

- if ((rb & DBELL_BRDCAST) || (cenv->spr[SPR_BOOKE_PIR] == pir)) {

+        if ((rb & DBELL_BRDCAST_MASK) || (cenv->spr[SPR_BOOKE_PIR] == pir)) {
              ppc_set_irq(cpu, irq, 1);
          }
      }
@@ -3104,6 +3104,16 @@ static bool dbell_type_server(target_ulong rb)
      return (rb & DBELL_TYPE_MASK) == DBELL_TYPE_DBELL_SERVER;
  }

+static inline bool dbell_type_bcast_core(target_ulong rb)

+{
+    return (rb & DBELL_BRDCAST_MASK) == DBELL_BRDCAST_CORE;
+}
+
+static inline bool dbell_type_bcast_subproc(target_ulong rb)
+{
+    return (rb & DBELL_BRDCAST_MASK) == DBELL_BRDCAST_SUBPROC;
+}
+
  void helper_book3s_msgclr(CPUPPCState *env, target_ulong rb)
  {
      if (!dbell_type_server(rb)) {
@@ -3113,32 +3123,40 @@ void helper_book3s_msgclr(CPUPPCState *env, 
target_ulong rb)
      ppc_set_irq(env_archcpu(env), PPC_INTERRUPT_HDOORBELL, 0);
  }

-static void book3s_msgsnd_common(int pir, int irq)

+void helper_book3s_msgsnd(CPUPPCState *env, target_ulong rb)
  {
-    CPUState *cs;
-
-    qemu_mutex_lock_iothread();
-    CPU_FOREACH(cs) {
-        PowerPCCPU *cpu = POWERPC_CPU(cs);
-        CPUPPCState *cenv = &cpu->env;
+    int pir = rb & DBELL_PROCIDTAG_MASK;
+    int brdcast = rb & DBELL_BRDCAST_MASK;
+    CPUState *cs, *ccs;
+    PowerPCCPU *cpu;

- /* TODO: broadcast message to all threads of the same processor */

-        if (cenv->spr_cb[SPR_PIR].default_value == pir) {
-            ppc_set_irq(cpu, irq, 1);
-        }
+    if (!dbell_type_server(rb)) {
+        return;
      }
-    qemu_mutex_unlock_iothread();
-}

-void helper_book3s_msgsnd(target_ulong rb)

-{
-    int pir = rb & DBELL_PROCIDTAG_MASK;
+    cpu = ppc_get_vcpu_by_pir(pir);
+    if (!cpu) {
+        return;
+    }
+    cs = CPU(cpu);

- if (!dbell_type_server(rb)) {

+    if (cs->nr_threads == 1 || !brdcast) {
+        ppc_set_irq(cpu, PPC_INTERRUPT_HDOORBELL, 1);
          return;
      }

- book3s_msgsnd_common(pir, PPC_INTERRUPT_HDOORBELL);

+    /* WHy does iothread need to be locked for walking CPU list? */
+    /* Answer seems to be because ppc irq handling needs it, but it now takes
+     * the lock itself if needed. Could remove this then.
+     */
+    qemu_mutex_lock_iothread();
+    THREAD_SIBLING_FOREACH(cs, ccs) {
+        PowerPCCPU *ccpu = POWERPC_CPU(ccs);
+        if (cpu != ccpu) {
+            ppc_set_irq(ccpu, PPC_INTERRUPT_HDOORBELL, 1);
+        }
+    }
+    qemu_mutex_unlock_iothread();
  }

#if defined(TARGET_PPC64)

@@ -3154,22 +3172,42 @@ void helper_book3s_msgclrp(CPUPPCState *env, 
target_ulong rb)
  }

/*

- * sends a message to other threads that are on the same
+ * sends a message to another thread  on the same
   * multi-threaded processor
   */
  void helper_book3s_msgsndp(CPUPPCState *env, target_ulong rb)
  {
-    int pir = env->spr_cb[SPR_PIR].default_value;
+    CPUState *cs = env_cpu(env);
+    PowerPCCPU *cpu = POWERPC_CPU(cs);
+    CPUState *ccs;
+    uint32_t nr_threads = cs->nr_threads;
+    int ttir = rb & PPC_BITMASK(57, 63);

helper_hfscr_facility_check(env, HFSCR_MSGP, "msgsndp", HFSCR_IC_MSGP);- if (!dbell_type_server(rb)) {

+    if (!dbell_type_server(rb) || ttir >= nr_threads) {


may be log bad ttir values ? even if the insn is a no-op in that case,
telling the user would be good since it should be a guest os issue

+        return;
+    }
+
+    if (nr_threads == 1) {
+        ppc_set_irq(cpu, PPC_INTERRUPT_DOORBELL, 1);
          return;
      }

- /* TODO: TCG supports only one thread */

+    /* WHy does iothread need to be locked for walking CPU list? */
+    qemu_mutex_lock_iothread();
+    THREAD_SIBLING_FOREACH(cs, ccs) {
+        PowerPCCPU *ccpu = POWERPC_CPU(ccs);
+        uint32_t thread_id = ppc_cpu_tir(ccpu);
+
+        if (ttir == thread_id) {
+            ppc_set_irq(ccpu, PPC_INTERRUPT_DOORBELL, 1);
+            qemu_mutex_unlock_iothread();
+            return;
+        }
+    }

- book3s_msgsnd_common(pir, PPC_INTERRUPT_DOORBELL);

+    assert(0);
  }
  #endif /* TARGET_PPC64 */

diff --git a/target/ppc/gdbstub.c b/target/ppc/gdbstub.c

index ca39efdc35..f0304e5bb6 100644
--- a/target/ppc/gdbstub.c
+++ b/target/ppc/gdbstub.c
@@ -117,7 +117,7 @@ void ppc_maybe_bswap_register(CPUPPCState *env, uint8_t 
*mem_buf, int len)
   * regs and PC, MSR, CR, and so forth.  We hack round this by giving
   * the FP regs zero size when talking to a newer gdb.
   */
-
+/* XXX: read/write dpdes correctly */
  int ppc_cpu_gdb_read_register(CPUState *cs, GByteArray *buf, int n)
  {
      PowerPCCPU *cpu = POWERPC_CPU(cs);
diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index fda40b8a60..5ce49c7ebc 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -690,7 +690,7 @@ DEF_HELPER_FLAGS_3(store_sr, TCG_CALL_NO_RWG, void, env, 
tl, tl)

DEF_HELPER_1(msgsnd, void, tl)

  DEF_HELPER_2(msgclr, void, env, tl)
-DEF_HELPER_1(book3s_msgsnd, void, tl)
+DEF_HELPER_2(book3s_msgsnd, void, env, tl)
  DEF_HELPER_2(book3s_msgclr, void, env, tl)
  #endif

diff --git a/target/ppc/misc_helper.c b/target/ppc/misc_helper.c

index ffe54a4310..ca84f1b134 100644
--- a/target/ppc/misc_helper.c
+++ b/target/ppc/misc_helper.c
@@ -192,14 +192,38 @@ void helper_store_pcr(CPUPPCState *env, target_ulong 
value)
   */
  target_ulong helper_load_dpdes(CPUPPCState *env)
  {
+    CPUState *cs = env_cpu(env);
+    CPUState *ccs;
+    uint32_t nr_threads = cs->nr_threads;
+    uint32_t core_id = env->spr[SPR_PIR] & ~(nr_threads - 1);


you could add an helper for the above.

      target_ulong dpdes = 0;

+ assert(core_id == env->spr[SPR_PIR] - env->spr[SPR_TIR]);

+
      helper_hfscr_facility_check(env, HFSCR_MSGP, "load DPDES", HFSCR_IC_MSGP);

- /* TODO: TCG supports only one thread */

-    if (env->pending_interrupts & PPC_INTERRUPT_DOORBELL) {
-        dpdes = 1;
+    if (nr_threads == 1) {
+        if (env->pending_interrupts & PPC_INTERRUPT_DOORBELL) {
+            dpdes = 1;
+        }
+        return dpdes;
+    }
+
+    qemu_mutex_lock_iothread();
+    CPU_FOREACH(ccs) {
+        CPUPPCState *cenv = &POWERPC_CPU(ccs)->env;
+        uint32_t ccore_id = cenv->spr[SPR_PIR] & ~(nr_threads - 1);
+        uint32_t thread_id = cenv->spr[SPR_TIR];
+
+        assert(ccore_id == cenv->spr[SPR_PIR] - cenv->spr[SPR_TIR]);
+
+        if (ccore_id == core_id) {
+            if (cenv->pending_interrupts & PPC_INTERRUPT_DOORBELL) {
+                dpdes |= (0x1 << thread_id);
+            }
+        }
      }
+    qemu_mutex_unlock_iothread();

return dpdes;

  }
@@ -207,17 +231,41 @@ target_ulong helper_load_dpdes(CPUPPCState *env)
  void helper_store_dpdes(CPUPPCState *env, target_ulong val)
  {
      PowerPCCPU *cpu = env_archcpu(env);
+    CPUState *cs = env_cpu(env);
+    CPUState *ccs;
+    uint32_t nr_threads = cs->nr_threads;
+    uint32_t core_id = env->spr[SPR_PIR] & ~(nr_threads - 1);
+
+    assert(core_id == env->spr[SPR_PIR] - env->spr[SPR_TIR]);

helper_hfscr_facility_check(env, HFSCR_MSGP, "store DPDES", HFSCR_IC_MSGP);- /* TODO: TCG supports only one thread */

-    if (val & ~0x1) {
+    if (val & ~(nr_threads - 1)) {
          qemu_log_mask(LOG_GUEST_ERROR, "Invalid DPDES register value "
                        TARGET_FMT_lx"\n", val);
+        val &= ~(nr_threads - 1);
+        /* Ignore the invalid bits */
+    }
+
+    if (nr_threads == 1) {
+        /* XXX: don't need iothread lock? */
+        ppc_set_irq(cpu, PPC_INTERRUPT_DOORBELL, val & 0x1);
          return;
      }

- ppc_set_irq(cpu, PPC_INTERRUPT_DOORBELL, val & 0x1);

+    qemu_mutex_lock_iothread();
+    CPU_FOREACH(ccs) {
+        CPUPPCState *cenv = &POWERPC_CPU(ccs)->env;
+        uint32_t ccore_id = cenv->spr[SPR_PIR] & ~(nr_threads - 1);
+        uint32_t thread_id = cenv->spr[SPR_TIR];
+
+        assert(ccore_id == cenv->spr[SPR_PIR] - cenv->spr[SPR_TIR]);
+
+        if (ccore_id == core_id) {
+            ppc_set_irq(cpu, PPC_INTERRUPT_DOORBELL, val & (0x1 << thread_id));
+        }
+    }
+    qemu_mutex_unlock_iothread();
  }
  #endif /* defined(TARGET_PPC64) */

diff --git a/target/ppc/translate.c b/target/ppc/translate.c

index 31821f92f5..0aa49323d3 100644
--- a/target/ppc/translate.c
+++ b/target/ppc/translate.c
@@ -820,11 +820,19 @@ void spr_write_pcr(DisasContext *ctx, int sprn, int gprn)
  /* DPDES */
  void spr_read_dpdes(DisasContext *ctx, int gprn, int sprn)
  {
+    if (!gen_serialize_core(ctx)) {
+        return;
+    }
+
      gen_helper_load_dpdes(cpu_gpr[gprn], cpu_env);
  }

void spr_write_dpdes(DisasContext *ctx, int sprn, int gprn)

  {
+    if (!gen_serialize_core(ctx)) {
+        return;
+    }
+
      gen_helper_store_dpdes(cpu_env, cpu_gpr[gprn]);
  }
  #endif
diff --git a/target/ppc/translate/processor-ctrl-impl.c.inc 
b/target/ppc/translate/processor-ctrl-impl.c.inc
index cc7a50d579..7dfbcd781f 100644
--- a/target/ppc/translate/processor-ctrl-impl.c.inc
+++ b/target/ppc/translate/processor-ctrl-impl.c.inc
@@ -59,7 +59,7 @@ static bool trans_MSGSND(DisasContext *ctx, arg_X_rb *a)

#if !defined(CONFIG_USER_ONLY)

      if (is_book3s_arch2x(ctx)) {
-        gen_helper_book3s_msgsnd(cpu_gpr[a->rb]);
+        gen_helper_book3s_msgsnd(cpu_env, cpu_gpr[a->rb]);
      } else {
          gen_helper_msgsnd(cpu_gpr[a->rb]);
      }

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