Re: [Xen-devel] [V10 PATCH 10/23] PVH xen: domain create, context switch related code changes

[Mukesh Rathor <mukesh.rathor@xxxxxxxxxx>]

On Fri, 16 Aug 2013 17:11:21 +0100
"Jan Beulich" <JBeulich@xxxxxxxx> wrote:

> >>> On 16.08.13 at 17:32, George Dunlap <George.Dunlap@xxxxxxxxxxxxx>
> >>> wrote:
> > On Wed, Jul 24, 2013 at 2:59 AM, Mukesh Rathor
......
> >>
> >>      set_bit(_VPF_in_reset, &v->pause_flags);
> >>
> >> + pvh_skip_pv_stuff:
> > 
> > Any idea what this set_bit(_VPF_in_reset) stuff is?  It looks like
> > it's set above, and cleared down near the bottom of the function if
> > nothing gets screwed up.
> 
> This is related to the preemptible vCPU reset (which
> arch_set_info_guest() just re-uses), making sure that while there
> is an incomplete state update for a vCPU 8because it may have got
> preempted) the vCPU can't be unpaused.
> 
> > It seems like if that set/clear pair is important, then PVH should
> > do them both as well, shouldn't it?
> 
> I thought I had checked this once - does it now bypass one of the
> two?
> 
> But then again, this is all about PV memory management, so perhaps
> it was that way when I checked, and I decided it was fine.

Ok, I'll just leave it as it is then. Setting it might confuse someone
why it's being set for PVH. Clearing is harmless anyways :).

thanks
mukesh

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