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Date: Mon, 09 Jan 2012 09:19:02 +0100
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Subject: Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer
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To: "Zhang, Yang Z" <yang.z.zhang@intel.com>
Cc: "aliguori@us.ibm.com" <aliguori@us.ibm.com>, "kvm@vger.kernel.org" <kvm@vger.kernel.org>, "Shan,
	Haitao" <haitao.shan@intel.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "avi@redhat.com" <avi@redhat.com>

On 01/06/2012 08:37 AM, Zhang, Yang Z wrote:
>           VMSTATE_BUFFER(cmos_data, RTCState),
>           VMSTATE_UINT8(cmos_index, RTCState),
> -        VMSTATE_INT32(current_tm.tm_sec, RTCState),
> -        VMSTATE_INT32(current_tm.tm_min, RTCState),
> -        VMSTATE_INT32(current_tm.tm_hour, RTCState),
> -        VMSTATE_INT32(current_tm.tm_wday, RTCState),
> -        VMSTATE_INT32(current_tm.tm_mday, RTCState),
> -        VMSTATE_INT32(current_tm.tm_mon, RTCState),
> -        VMSTATE_INT32(current_tm.tm_year, RTCState),
> +        VMSTATE_INT64(offset, RTCState),
>           VMSTATE_TIMER(periodic_timer, RTCState),
>           VMSTATE_INT64(next_periodic_time, RTCState),
> -        VMSTATE_INT64(next_second_time, RTCState),
> -        VMSTATE_TIMER(second_timer, RTCState),
> -        VMSTATE_TIMER(second_timer2, RTCState),
> +        VMSTATE_TIMER(update_timer, RTCState),
> +        VMSTATE_INT64(next_update_time, RTCState),
> +        VMSTATE_TIMER(alarm_timer, RTCState),
> +        VMSTATE_INT64(next_alarm_time, RTCState),

Hi Yang,

this looks like a very nice piece of work, but this unfortunately breaks 
migration.  Also, I'm not sure if the update in progress flag still 
works.  Clients are supposed to wait for UIP=0 before reading the RTC, 
and an update is supposed to be at least 220 microseconds away when UIP=0.

Also, it would be nice if you could based these patches on the 4-patch 
series I sent recently that fixes some bugs with interrupts and 12-hour 
emulation.

There is another aspect of RTC emulation that is missing in the current 
code; after setting the clock, the next second tick will occur in 
exactly 500 ms.  I have patches to fix this, but it looks like it could 
be incorporated in your series, too.

Paolo