Re: [Xen-devel] Device pass through on XEN on ARM

[Gordan Bobic <gordan@xxxxxxxxxx>]

On 2014-06-11 10:42, Ian Campbell wrote:
> On Wed, 2014-06-11 at 11:16 +0200, Khandelwal, Shubham wrote:
> > Just to try out the passthrough using the hacks you mentioned, I made
> > changes in xen to assign a GPIO controlled LED to domU by calling
> > map_mmio_regions() in the domain creation path. After domU boots, when
> > I try to access the LED using ioremap, ioread and iowrite from kernel
> > space I see that I am not able to control the LED,
> How does it fail? Does it give a fault in the hypervisor or the guest
> kernel or just silently eat the MMIO writes and not do anything?
>
> >  also when I try to control LED using sysfs from user space it shows
> > 'no such device' error.
> >
> > I am using xen 4.5 unstable and I have made the following changes in
> > xen/common/domctl.c :: do_domctl(), after line 473:
> >
> >
> >
> > int passthrough = map_mmio_regions(d, 0x4805B000, 0x4805B000 + 0x1000, 
> > 0x4805B000);
> > if (passthrough)
> >         printk("Failed to map passthrough_LED @ 0x4805B000 to 
> > dom%d\n", d->domain_id);
> >
> >
> > While booting domU, in the logs I can see there is no error in
> > map_mmio_regions(). Am I missing something here.
> 0x4xxxxxxx is a RAM region on 4.5 (see the end of
> xen/include/public/arch-arm.h), I suspect your mmio mapping is being
> clobbered by a RAM mapping (and therefore that your answer above is
> "silently does nothing".
>
> Do you need this to be a 1:1 mapping or could you move it to some free
> space? Most of the low GB is free (but do check arch-arm.h) to be used
> for MMIO mappings.
I have a sneaky suspicion that part of the problem is that the
offending BAR is 16GB in size.

Gordan

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel