From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:44383) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TZjjD-00054Z-U6 for qemu-devel@nongnu.org; Sat, 17 Nov 2012 09:50:42 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TZjjA-0003QA-S3 for qemu-devel@nongnu.org; Sat, 17 Nov 2012 09:50:39 -0500 Received: from indium.canonical.com ([91.189.90.7]:52153) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TZjjA-0003Q3-MI for qemu-devel@nongnu.org; Sat, 17 Nov 2012 09:50:36 -0500 Received: from loganberry.canonical.com ([91.189.90.37]) by indium.canonical.com with esmtp (Exim 4.71 #1 (Debian)) id 1TZjj9-0002E4-4s for ; Sat, 17 Nov 2012 14:50:35 +0000 Received: from loganberry.canonical.com (localhost [127.0.0.1]) by loganberry.canonical.com (Postfix) with ESMTP id 165982E8070 for ; Sat, 17 Nov 2012 14:50:35 +0000 (UTC) MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: quoted-printable Date: Sat, 17 Nov 2012 14:41:35 -0000 From: Alex Horn Sender: bounces@canonical.com References: <20121117144135.13758.80176.malonedeb@wampee.canonical.com> Message-Id: <20121117144135.13758.80176.malonedeb@wampee.canonical.com> Errors-To: bounces@canonical.com Subject: [Qemu-devel] [Bug 1080086] [NEW] MC146818 RTC breaks when SET bit in Register B is on. Reply-To: Bug 1080086 <1080086@bugs.launchpad.net> List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Public bug reported: This bug occurs when the SET flag of Register B is enabled. When an RTC data register (i.e. any of the 10 bytes of time/calender data in CMOS) is s= et, the data is (as expected) correctly stored in the cmos_data array. However, since the SET flag is enabled, the function rtc_set_time is not invoked. As a result, the field base_rtc in RTCState remains uninitialized. This app= ears to cause a problem on subsequent writes which can end up overwriting data. To see this, consider writing data to Register A after having written data to any of the RTC data registers; the following figure illustrates the call stack for the Register A write operation: +- cmos_io_port_write +-- check_update_timer +---- get_next_alarm +------ rtc_update_time In rtc_update_time, get_guest_rtc calculates the wrong time and overwrites the previously written RTC data register values. I have created a standalone test case which exposes this bug: https://github.com/ahorn/benchmarks/commit/fff1ca40694bbef6f7f9de323bb0bed6= 3419ef99 ** Affects: qemu Importance: Undecided Status: New ** Tags: rtc -- = You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1080086 Title: MC146818 RTC breaks when SET bit in Register B is on. Status in QEMU: New Bug description: This bug occurs when the SET flag of Register B is enabled. When an RTC data register (i.e. any of the 10 bytes of time/calender data in CMOS) is= set, the data is (as expected) correctly stored in the cmos_data array. Howeve= r, since the SET flag is enabled, the function rtc_set_time is not invoked. As a result, the field base_rtc in RTCState remains uninitialized. This a= ppears to cause a problem on subsequent writes which can end up overwriting data. To see this, consider writing data to Register A after having written data to any of the RTC data registers; the following figure illustrates the call stack for the Register A write operation: +- cmos_io_port_write +-- check_update_timer +---- get_next_alarm +------ rtc_update_time In rtc_update_time, get_guest_rtc calculates the wrong time and overwrites the previously written RTC data register values. I have created a standalone test case which exposes this bug: https://github.com/ahorn/benchmarks/commit/fff1ca40694bbef6f7f9de323bb0be= d63419ef99 To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1080086/+subscriptions