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Re: [libvirt] [PATCH 09/14] Fix check for whether a suspend target is supported



On Tue, Nov 29, 2011 at 10:23:25PM +0530, Srivatsa S. Bhat wrote:
> On 11/29/2011 10:10 PM, Daniel P. Berrange wrote:
> 
> > On Tue, Nov 29, 2011 at 09:33:09AM -0700, Eric Blake wrote:
> >> On 11/29/2011 08:44 AM, Daniel P. Berrange wrote:
> >>> From: "Daniel P. Berrange" <berrange redhat com>
> >>>
> >>> hostPMFeatures is a bitmask, but the VIR_NODE_SUSPEND_TARGET
> >>> constants are from an enum. Thus the code was checking the
> >>> wrong bit values
> >>
> >> Yep - regression introduced in patch 1/14.  Maybe you should squash this
> >> in to that patch, so that bisecting doesn't hit the regression (although
> >> that would mean patching a different file, since you moved the function
> >> location in the meantime).  Up to you if you want to go to the hassle.
> > 
> > It wasn't a regression actually. This code was still using the
> > duplicate enum at that point:
> > 
> >   enum virHostPMCapability {
> >      VIR_HOST_PM_S3,              /* Suspend-to-RAM */
> >      VIR_HOST_PM_S4,              /* Suspend-to-Disk */
> >      VIR_HOST_PM_HYBRID_SUSPEND,  /* Hybrid-Suspend */
> > 
> >      VIR_HOST_PM_LAST
> >  };
> > 
> > So AFAICT, it was broken from the start.
> > 
> 
> 
> I beg to differ here. It was a bit weird, but definitely not broken.
> Since VIR_HOST_PM_S3 etc were linear (0,1,2), a bit-wise OR operation
> was carried out like this: *bitmask |= 1U << feature; where feature
> was one of the above.
> 
> And while checking this, we used to do:
> hostPMFeatures & VIR_NODE_SUSPEND_TARGET_HYBRID
> 
> where VIR_NODE_SUSPEND_TARGET_HYBRID etc were like 1 << 0, 1 << 1 etc
> 
> Thus, this was ugly, but not broken. Otherwise, it would have surely
> failed my suspend tests which I ran every time before submitting the
> patches :-)

Actually yes you are right. I was confusing two bits of code

Daniel
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