Re: [Xen-devel] [RFC Patch v2 45/45] x86/hvm: Always set pending event injection when loading VMC[BS] state.

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxx [mailto:xen-devel-
> bounces@xxxxxxxxxxxxx] On Behalf Of Wen Congyang
> Sent: 28 August 2014 12:18
> To: Andrew Cooper; Aravind Gopalakrishnan; Jan Beulich
> Cc: Kevin Tian; Yang Hongyang; Ian Campbell; Eddie Dong; Ian Jackson; Tim
> (Xen.org); Jun Nakajima; Boris Ostrovsky; xen devel;
> suravee.suthikulpanit@xxxxxxx; Lai Jiangshan
> Subject: Re: [Xen-devel] [RFC Patch v2 45/45] x86/hvm: Always set pending
> event injection when loading VMC[BS] state.
> 
> At 08/28/2014 04:54 PM, Andrew Cooper Write:
> > On 28/08/14 02:04, Wen Congyang wrote:
> >> At 08/27/2014 10:58 PM, Aravind Gopalakrishnan Write:
> >>> On 8/26/2014 7:46 PM, Wen Congyang wrote:
> >>>> At 08/27/2014 12:02 AM, Jan Beulich Write:
> >>>>>>>> On 08.08.14 at 09:01, <wency@xxxxxxxxxxxxxx> wrote:
> >>>>>> In colo mode, secondary vm is running, so VM_ENTRY_INTR_INFO
> may
> >>>>>> valid before restoring vmcs. If there is no pending event after
> >>>>>> restoring vm, we should clear it.
> >>>>>>
> >>>>>> Signed-off-by: Wen Congyang <wency@xxxxxxxxxxxxxx>
> >>>>>>
> >>>>>> Also clear pending software exceptions.
> >>>>>> Copy the fix to SVM as well.
> >>>>>>
> >>>>>> Signed-off-by: Tim Deegan <tim@xxxxxxx>
> >>>>> I only now realized that it's no surprise we're not getting acks from
> >>>>> the VMX maintainers on this - the majority of them wasn't Cc-ed.
> >>>>> Now done, but please take care to do so yourself in the future.
> >>>>>
> >>>>> As to the SVM maintainers - Ping (I Cc-ed you on an earlier reply)?
> >>>> Thanks for doing this.
> >>>> I have repost it in the bugfix patchset, and cc vmx and svm maintainers
> >>>>
> >>> Hi,
> >>> Apologies for the delay.
> >>>
> >>> As for the svm changes, the patch seems fairly straightforward and
> harmless.
> >>> However, I am not familiar with 'colo mode', so I'm not sure I understand
> the problem..
> >> In colo mode, secondary vm runs like this:
> >> 1. suspend
> >> 2. update the vm's state(All state is transfered from primary)
> >> 3. resume
> >
> > Is this accurate?  From previous review, I seem to remember that you are
> > pausing the vm, not suspending it, which is where all of these event
> > issues derive from.
> 
> Not pause. We suspend the guest(not save the state). Pausing vm meant
> that
> the vm is not running, but the state cannot be updated. For example, if the
> vm uses pvdriver(not supported now), the backend and frontend share
> some
> information, and we only update frontend(backend state is not transfered
> from primary dom0)...
> 

If you're doing suspend/resume then PV drivers should re-attached to backends 
anyway so any state you did transfer would be somewhat pointless. Because of 
the re-attach though, resume is a pretty heavyweight operation. Is that really 
what you are doing?

  Paul


> Thanks
> Wen Congyang
> 
> >
> > ~Andrew
> > .
> >
> 
> 
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