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Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer
From: |
Marcelo Tosatti |
Subject: |
Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer |
Date: |
Thu, 12 Jan 2012 08:03:08 -0200 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
On Thu, Jan 12, 2012 at 07:59:06AM -0200, Marcelo Tosatti wrote:
> On Thu, Jan 12, 2012 at 12:00:06AM +0000, Zhang, Yang Z wrote:
> > > -----Original Message-----
> > > From: Marcelo Tosatti [mailto:address@hidden
> > >
> > > Regarding the UIP bit, a guest could read it in a loop and wait for the
> > > value to
> > > change. But you can emulate it in cmos_ioport_read by reading the host
> > > time,
> > > that is, return 1 during 244us, 0 for remaining of the second, and have
> > > that in sync
> > > with update-cycle-ended interrupt if its enabled.
> > Yes. Guest may use the loop to read RTC, but the point is the guest is
> > waiting for the UIP changed to 0. If this bit always equal to 0 , guest
> > will never go into the loop. For real RTC, this may wrong, because the RTC
> > cannot give you the valid value during the update cycle. But the virtual
> > RTC doesn't' need this logic, whenever you read it, it will always return
> > the right value to you.
>
> Can't it wait a change from 0 to 1?
The point is the guest can use the hardware as it pleases,
not only as is suggested in the hardware documentation.
- Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, (continued)
- Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Zhang, Yang Z, 2012/01/10
- Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Philipp Hahn, 2012/01/11
- Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Paolo Bonzini, 2012/01/11
- Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Zhang, Yang Z, 2012/01/11
Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Marcelo Tosatti, 2012/01/11
Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Marcelo Tosatti, 2012/01/12
Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer,
Marcelo Tosatti <=
Re: [Qemu-devel] [PATCH 3/3] stop the periodic RTC update timer, Zhang, Yang Z, 2012/01/12