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[PULL,16/67] hw/ppc: fix decrementer with BookE timers

Message ID 20241104001900.682660-17-npiggin@gmail.com (mailing list archive)
State New
Headers show
Series [PULL,01/67] target/ppc: Set ctx->opcode for decode_insn32() | expand

Commit Message

Nicholas Piggin Nov. 4, 2024, 12:18 a.m. UTC 
From: Clément Chigot <chigot@adacore.com>

The BookE decrementer stops at 0, meaning that it won't decremented
towards "negative" values. However, the current logic is inverted: decr
is updated solely when the resulting value would be negative.

Signed-off-by: Clément Chigot <chigot@adacore.com>
Fixes: 8e0a5ac87800 ("hw/ppc: Avoid decrementer rounding errors")
Reviewed-by: Cédric Le Goater <clg@redhat.com>
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 hw/ppc/ppc.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)
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Patch

diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c
index fde4619412..b86b5847de 100644
--- a/hw/ppc/ppc.c
+++ b/hw/ppc/ppc.c
@@ -728,7 +728,9 @@  static inline int64_t __cpu_ppc_load_decr(CPUPPCState *env, int64_t now,
     int64_t decr;
 
     n = ns_to_tb(tb_env->decr_freq, now);
-    if (next > n && tb_env->flags & PPC_TIMER_BOOKE) {
+
+    /* BookE timers stop when reaching 0.  */
+    if (next < n && tb_env->flags & PPC_TIMER_BOOKE) {
         decr = 0;
     } else {
         decr = next - n;