From e8291ec16da80566c121c68d9112be458954d90b Mon Sep 17 00:00:00 2001 From: Nicholas Piggin Date: Thu, 19 Dec 2024 13:40:31 +1000 Subject: [PATCH] target/ppc: fix timebase register reset state (H)DEC and PURR get reset before icount does, which causes them to be skewed and not match the init state. This can cause replay to not match the recorded trace exactly. For DEC and HDEC this is usually not noticable since they tend to get programmed before affecting the target machine. PURR has been observed to cause replay bugs when running Linux. Fix this by resetting using a time of 0. Message-ID: <20241219034035.1826173-2-npiggin@gmail.com> Signed-off-by: Nicholas Piggin --- hw/ppc/ppc.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/hw/ppc/ppc.c b/hw/ppc/ppc.c index 90e3db5cfe..3a80931538 100644 --- a/hw/ppc/ppc.c +++ b/hw/ppc/ppc.c @@ -1123,16 +1123,21 @@ void cpu_ppc_tb_reset(CPUPPCState *env) timer_del(tb_env->hdecr_timer); ppc_set_irq(cpu, PPC_INTERRUPT_HDECR, 0); tb_env->hdecr_next = 0; + _cpu_ppc_store_hdecr(cpu, 0, 0, 0, 64); } /* * There is a bug in Linux 2.4 kernels: * if a decrementer exception is pending when it enables msr_ee at startup, * it's not ready to handle it... + * + * On machine reset, this is called before icount is reset, so for + * icount-mode, setting TB registers using now == qemu_clock_get_ns() + * results in them being garbage after icount is reset. Use an + * explicit now == 0 to get a consistent reset state. */ - cpu_ppc_store_decr(env, -1); - cpu_ppc_store_hdecr(env, -1); - cpu_ppc_store_purr(env, 0x0000000000000000ULL); + _cpu_ppc_store_decr(cpu, 0, 0, -1, 64); + _cpu_ppc_store_purr(env, 0, 0); } void cpu_ppc_tb_free(CPUPPCState *env) -- 2.39.5