From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:47097) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cRUkG-0003Fk-Tn for qemu-devel@nongnu.org; Wed, 11 Jan 2017 21:04:08 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cRUkD-0006pO-U4 for qemu-devel@nongnu.org; Wed, 11 Jan 2017 21:04:04 -0500 From: David Gibson Date: Thu, 12 Jan 2017 13:03:26 +1100 Message-Id: <20170112020327.24882-67-david@gibson.dropbear.id.au> In-Reply-To: <20170112020327.24882-1-david@gibson.dropbear.id.au> References: <20170112020327.24882-1-david@gibson.dropbear.id.au> Subject: [Qemu-devel] [PULL 66/67] ppc: Prevent inifnite loop in decrementer auto-reload. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: peter.maydell@linaro.org Cc: agraf@suse.de, qemu-ppc@nongnu.org, qemu-devel@nongnu.org, thuth@redhat.com, lvivier@redhat.com, aik@ozlabs.ru, mdroth@linux.vnet.ibm.com, Roman Kapl , David Gibson From: Roman Kapl If the DECAR register is set to 0, QEMU tries to reload the decrementer with zero in an inifinite loop. According to PPC documentation, the decrementer is triggered on 1->0 transition, so avoid reloading the decrementer if if is already zero. The problem does not manifest under Linux, but it is valid to set DECAR to zero (and may make sense as part of decrementer initialization when interrupts are disabled). Signed-off-by: Roman Kapl [dwg: Fixed style nit] Signed-off-by: David Gibson --- hw/ppc/ppc_booke.c | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) diff --git a/hw/ppc/ppc_booke.c b/hw/ppc/ppc_booke.c index ab8d026..60baffa 100644 --- a/hw/ppc/ppc_booke.c +++ b/hw/ppc/ppc_booke.c @@ -198,8 +198,12 @@ static void booke_decr_cb(void *opaque) booke_update_irq(cpu); if (env->spr[SPR_BOOKE_TCR] & TCR_ARE) { - /* Auto Reload */ - cpu_ppc_store_decr(env, env->spr[SPR_BOOKE_DECAR]); + /* Do not reload 0, it is already there. It would just trigger + * the timer again and lead to infinite loop */ + if (env->spr[SPR_BOOKE_DECAR] != 0) { + /* Auto Reload */ + cpu_ppc_store_decr(env, env->spr[SPR_BOOKE_DECAR]); + } } } -- 2.9.3