From 7f516cdeef6d62e78ee769855dff95666e6b8c1d Mon Sep 17 00:00:00 2001
From: Nicholas Piggin <npiggin@gmail.com>
Date: Sat, 6 Jul 2024 13:22:58 +1000
Subject: [PATCH] target/ppc: Fix msgsnd for POWER8
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POWER8 (ISA v2.07S) introduced the doorbell facility, the msgsnd
instruction behaved mostly like msgsndp, it was addressed by TIR
and could only send interrupts between threads on the core.

ISA v3.0 changed msgsnd to be addressed by PIR and can interrupt
any thread in the system.

msgsnd only implements the v3.0 semantics, which can make
multi-threaded POWER8 hang when booting Linux (due to IPIs
failing). This change adds v2.07 semantics.

Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 target/ppc/excp_helper.c | 74 ++++++++++++++++++++++++----------------
 1 file changed, 44 insertions(+), 30 deletions(-)

diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c
index 0cd542675f..c0120c8a88 100644
--- a/target/ppc/excp_helper.c
+++ b/target/ppc/excp_helper.c
@@ -2998,6 +2998,41 @@ static inline bool dbell_bcast_subproc(target_ulong rb)
     return (rb & DBELL_BRDCAST_MASK) == DBELL_BRDCAST_SUBPROC;
 }
 
+/*
+ * Send an interrupt to a thread in the same core as env).
+ */
+static void msgsnd_core_tir(CPUPPCState *env, uint32_t target_tir, int irq)
+{
+    PowerPCCPU *cpu = env_archcpu(env);
+    CPUState *cs = env_cpu(env);
+    uint32_t nr_threads = cs->nr_threads;
+
+    if (!(env->flags & POWERPC_FLAG_SMT_1LPAR)) {
+        nr_threads = 1; /* msgsndp behaves as 1-thread in LPAR-per-thread mode*/
+    }
+
+    if (target_tir >= nr_threads) {
+        return;
+    }
+
+    if (nr_threads == 1) {
+        ppc_set_irq(cpu, irq, 1);
+    } else {
+        CPUState *ccs;
+
+        /* Does iothread need to be locked for walking CPU list? */
+        bql_lock();
+        THREAD_SIBLING_FOREACH(cs, ccs) {
+            PowerPCCPU *ccpu = POWERPC_CPU(ccs);
+            if (target_tir == ppc_cpu_tir(ccpu)) {
+                ppc_set_irq(ccpu, irq, 1);
+                break;
+            }
+        }
+        bql_unlock();
+    }
+}
+
 void helper_book3s_msgclr(CPUPPCState *env, target_ulong rb)
 {
     if (!dbell_type_server(rb)) {
@@ -3018,6 +3053,13 @@ void helper_book3s_msgsnd(CPUPPCState *env, target_ulong rb)
         return;
     }
 
+    /* POWER8 msgsnd is like msgsndp (targets a thread within core) */
+    if (!(env->insns_flags2 & PPC2_ISA300)) {
+        msgsnd_core_tir(env, rb & PPC_BITMASK(57, 63), PPC_INTERRUPT_HDOORBELL);
+        return;
+    }
+
+    /* POWER9 and later msgsnd is a global (targets any thread) */
     cpu = ppc_get_vcpu_by_pir(pir);
     if (!cpu) {
         return;
@@ -3064,41 +3106,13 @@ void helper_book3s_msgclrp(CPUPPCState *env, target_ulong rb)
  */
 void helper_book3s_msgsndp(CPUPPCState *env, target_ulong rb)
 {
-    CPUState *cs = env_cpu(env);
-    PowerPCCPU *cpu = env_archcpu(env);
-    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 (!(env->flags & POWERPC_FLAG_SMT_1LPAR)) {
-        nr_threads = 1; /* msgsndp behaves as 1-thread in LPAR-per-thread mode*/
-    }
-
-    if (!dbell_type_server(rb) || ttir >= nr_threads) {
+    if (!dbell_type_server(rb)) {
         return;
     }
 
-    if (nr_threads == 1) {
-        ppc_set_irq(cpu, PPC_INTERRUPT_DOORBELL, 1);
-        return;
-    }
-
-    /* Does iothread need to be locked for walking CPU list? */
-    bql_lock();
-    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);
-            bql_unlock();
-            return;
-        }
-    }
-
-    g_assert_not_reached();
+    msgsnd_core_tir(env, rb & PPC_BITMASK(57, 63), PPC_INTERRUPT_DOORBELL);
 }
 #endif /* TARGET_PPC64 */