From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:38506) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WH4LH-0007mv-6m for qemu-devel@nongnu.org; Fri, 21 Feb 2014 23:37:40 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WH4LC-0006hA-64 for qemu-devel@nongnu.org; Fri, 21 Feb 2014 23:37:35 -0500 Received: from legacy.ddn.com ([64.47.133.206]:6991 helo=dermtp01.datadirect.datadirectnet.com) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WH4LC-0006gh-0S for qemu-devel@nongnu.org; Fri, 21 Feb 2014 23:37:30 -0500 Message-ID: <53082983.4090000@ddn.com> Date: Fri, 21 Feb 2014 21:37:23 -0700 From: Matt Lupfer MIME-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Subject: [Qemu-devel] [PATCH] Don't enable a HPET timer if HPET is disabled List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: QEMU Developers Cc: pbonzini@redhat.com, Alex Bligh A HPET timer can be started when HPET is not yet enabled. This will not generate an interrupt to the guest, but causes problems when HPET is later enabled. A timer that is created and expires at least once before HPET is enabled will have an initialized comparator based on a hpet_offset of 0 (uninitialized). When HPET is enabled, hpet_set_timer() is called a second time, which modifies the timer expiry to a time based on the difference between current ticks (measured with the newly initialized hpet_offset) and the timer's comparator (which was generated before hpet_offset was initialized). This results in a long period of no HPET timer ticks. When this occurs with a CentOS 5.x guest, the guest may not receive timer interrupts during its narrow timer check window and panic on boot. Signed-off-by: Matt Lupfer --- hw/timer/hpet.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/hw/timer/hpet.c b/hw/timer/hpet.c index 1264dfd..e15d6bc 100644 --- a/hw/timer/hpet.c +++ b/hw/timer/hpet.c @@ -506,7 +506,8 @@ static void hpet_ram_write(void *opaque, hwaddr addr, timer->cmp = (uint32_t)timer->cmp; timer->period = (uint32_t)timer->period; } - if (activating_bit(old_val, new_val, HPET_TN_ENABLE)) { + if (activating_bit(old_val, new_val, HPET_TN_ENABLE) && + hpet_enabled(s)) { hpet_set_timer(timer); } else if (deactivating_bit(old_val, new_val, HPET_TN_ENABLE)) { hpet_del_timer(timer); -- 1.8.5.3