Re: [Xen-devel] Compilation error crossbuilding tools.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Tue, 9 Apr 2013, Sander Bogaert wrote:
> On 8 April 2013 19:08, Stefano Stabellini
> <stefano.stabellini@xxxxxxxxxxxxx> wrote:
> >
> > On Mon, 8 Apr 2013, Ian Jackson wrote:
> > > Stefano Stabellini writes ("Re: [Xen-devel] Compilation error 
> > > crossbuilding tools."):
> > > > On Mon, 8 Apr 2013, Ian Jackson wrote:
> > > > > The problem seems to be that the return
> > > > > value from lseek is being passed to printf(PRIx64).  I guess we have
> > > > > FILE_OFFSET_BITS=64 or some such so that the return value from lseek
> > > > > is 32-bit.
> > >
> > > I meant =32 of course.
> > >
> > > > Yes, you are right.
> > >
> > > tools/blktap is never going to be supported on arm, is it ?
> >
> > Correct
> >
> >
> > > So perhaps the right answer is just to disable the build.
> >
> > I agree, we should just disable it.
> >
> >
> > > But we should figure out how to set FILE_OFFSET_BITS=64 anyway perhaps ?
> >
> > indeed
> 
> I disabled blktap and blktap2 in Makefile & Rules.mk, I would attach a
> patch but what I did is not very clean :-) It would be disabled for
> all linux builds. I didn't see a way to differentiate in architectures
> in those files. The tools build fine now.
> 
> In response to Julien, after a relogin things worked as described.
> I'll add this small caveat to the wiki.
> 
> A question: why is it blktap wouldn't be used on ARM?
> 
> I think I fail to see the big difference between blktap and the
> 'classic' blkback & blkfront split driver approach. I read the wiki
> entry and the original notes from the blktap author. Is this correct:
> the domU blktap driver is like dom0's blkback driver and the userspace
> tools replace the classic domU's blkfront part?

blktap is just the block backend, alternative to blkback.
However blktap has a complex architecture and needs a kernel module as
well as some userspace libraries.


> This provides a more
> abstract interface to userspace allowing more 'freedom' in accessing
> the disk from domU userspace?

The blktap kernel module has never gone upstream in Linux.
xl can use QEMU as block backend, providing most of the features
bltkap provides, without the need for a kernel module.

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