Re: LAPIC soft-disable vs. LVT masking

[Sheng Yang <yasker@gmail.com>]

On Mon, Oct 20, 2008 at 05:46:35PM +0800, Yang, Sheng wrote:
> On Monday 20 October 2008 16:49:11 Jan Kiszka wrote:
> > Hi Sheng,
> >
> > obviously, I meditated too long over the APIC specs and VAPIC code of
> > KVM: When the guest resets the soft-enable bit in SVR, the in-kernel
> > APIC implementation also set the LVT masked bits - so far, so fine
> > (according to specs). But I failed to read out of that doc if those mask
> > bits are permanently set (until the guest clears them again) or only
> > until the soft-disabling ends (ie. they are restored to their previous
> > state - QEMU goes this way). Can you clarify?
> >
> > Thanks,
> > Jan
> >
> Hi Jan
> 
> I also can't find related info in the spec. But I think, when software enable 
> bit is cleaned, the spec said the mask bits are set, which means the content 
> of register is changed. And no words for what happen if set software enable 
> bit, so I think it maybe retain the mask state after software enable (a 
> little more possibility).
> 
> I will give a update if I got more infos.

Find some info:

SDM 3A 8.5.1 Local Vector Table
Mask:
[...] This flag would remain set until software clears it.

I think this can explain it.

If you got some interesting circumstance, please share with us. :)

--
regards
Yang, Sheng