Re: [Xen-devel] [PATCH v3] gcov: add new interface and 3.4 and 4.7 format support

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Wed, Oct 12, 2016 at 02:26:26PM +0100, George Dunlap wrote:
[...]
> >>
> >> There is a version field in gcov_info, so we can compare that and reject
> >> incompatible version.
> >>
> >> We need to use hooks in livepatching to call the constructor /
> >> destructor when applying / reverting a live-patch.  We might need to be
> >> cautious about locks or whatever, but I'm sure it can be figured out.
> >>
> >> But I have no idea how useful it would be to use gcov and livepatching
> >> together.  For now the easiest thing to do is to
> >>
> >>    depends on !LIVEPATCH
> >>
> >> in Kconfig.
> > 
> > Wouldn't it be just as easy, and more useful, to set a "has been
> > livepatched" flag, and return errors for all gcov hypercalls if its' set?
> > 
> > I would expect most users to want to build a single hypervisor that can
> > be used for both gcov testing and live patching (under different
> > circumstances).
> 
> I mean software provider, not user, of course.  That's what I would want
> for CentOS, and I'm sure that's what the XenServer (and probably Oracle)
> guys want as well.
> 

The usefulness of such build is not as big as you might think I'm
afraid -- it wouldn't be useful until we figure out how to apply a
livepatch generated with gcov support built in.

Wei.

>  -George
> 

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