Re: [Xen-devel] [PATCH] Improve the current FLR logic

[Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>]

> Yuji Shimada wrote:
> > On Wed, 23 Jul 2008 11:16:31 +0800
> > "Cui, Dexuan" <dexuan.cui@xxxxxxxxx> wrote:
> >> I think xenstore seems to be a little ugly place to remember the
> >> proper values of all or part of registers of all the devices in the
> >> system. 
> >> I agree pciback is a good place.
> >> Yes. Now I realize pciback seems to be the best place to do most of
> >> the FLR logic. But this needs modify pciback and add interfaces for
> >> Control Panel. I'm not sure the changes can be small enought to be
> >> in 3.3. 
> > 
> > Hi Cui,
> > 
> > What do you think about the following idea?
> >   - For 3.3, modify xend to have limited saving/restoring and
> >     resetting functions.
> >   - For 3.4, modify pciback to have proper saving/restoring and
> >     resetting functions.
> Hi Yuji,
> Thanks very much for the suggestions!
> I agree.
> 
> > The purpose of saving is to save the values configured by firmware. So
> > the best timing of saving the value is when dom0 starts. But if saving
> > the values when dom0 starts, pciback is the best place to
> > save/restore. If pciback saves/restores the values, we need many
> > codings. So it is difficult to achieve it in 3.3.
> > 
> > So for 3.3, there is a way that saving the value just before
> > resetting. It is possible xend saves/restores the value, I think. In
> 
> In current code of xend,
> The steps are:
> 1) save the current values of the configuration space registers
> 2) do_FLR
> 3) restore the values of the registers
> 
> "a way that saving the value just before resetting." -- do you mean the
> same thing? 
> 

Hi Cui,

Yes, I mean the same thing. But in current code of xend, xend saves all
Configuration Registers. The only registers I suggested before should be
saved. Small modification is needed.

> > this case, xend don't need saving the values in xenstore. Because
> > interval between saving and restoring is small.
> > 
> > My idea is summarized as follows:
> > 
> > Xen    Timing              Where      Difficulty
> > 3.3    before resetting    xend       easy
> > 3.4    when Dom0 starts    pciback    hard
> > 
> I exactly agree with you.
> 

Thanks.
--
Yuji Shimada

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