Re: [Xen-devel] [PATCH] tools: libxl: do not set the PoD target on ARM

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2014-01-28 at 14:28 +0000, George Dunlap wrote:
> On Tue, Jan 28, 2014 at 10:47 AM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> 
> wrote:
> > On Thu, 2014-01-16 at 15:27 +0000, Ian Campbell wrote:
> >> ARM does not implemented PoD and so returns ENOSYS from 
> >> XENMEM_set_pod_target.
> >>
> >> The correct solution here would be to check for ENOSYS in libxl, 
> >> unfortunately
> >> xc_domain_set_pod_target suffers from the same broken error reporting as 
> >> the
> >> rest of libxc and throws away the errno.
> >>
> >> So for now conditionally define xc_domain_set_pod_target to return success
> >> (which is what PoD does if nothing needs doing). xc_domain_get_pod_target 
> >> sets
> >> errno==-1 and returns -1, which matches the broken error reporting of the
> >> existing function. It appears to have no in tree callers in any case.
> >>
> >> The conditional should be removed once libxc has been fixed.
> >>
> >> This makes ballooning (xl mem-set) work for ARM domains.
> >>
> >> Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>
> >> Cc: george.dunlap@xxxxxxxxxx
> >> ---
> >> I'd be generally wary of modifying the error handling in a piecemeal way, 
> >> but
> >> certainly doing so for 4.4 now would be inapropriate.
> >>
> >> IIRC Ian J was planning a thorough sweep of the libxc error paths in 4.5 
> >> time
> >> frame, at which point this conditional stuff could be dropped.
> >>
> >> In terms of the 4.4 release, obviously ballooning would be very nice to 
> >> have
> >> for ARM guests, on the other hand I'm aware that while the patch is fairly
> >> small/contained and safe it is also pretty skanky and likely wouldn't be
> >> accepted outside of the rc period.
> >
> > George -- what do you think of this?
> 
> So is this actually called in the arm domain build code at the moment?

It is common code in libxl which calls into it. I originally had the
ifdef there instead.

(I've just noticed that I forgot to update $subject when I moved the
#ifdef from libxl to libxc)

Ian.


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