Re: [Xen-devel] Basic bare metal ARM domain interface

[Julien Grall <julien.grall@xxxxxxx>]

On 07/06/16 00:31, Ivan Pavic wrote:
> Hello Julien,
Hello Ivan,

> On Fri, Jun 03, 2016 at 11:23:33AM +0100, Julien Grall wrote:
> > On 02/06/16 20:09, Ivan Pavic wrote:
> > > Hello Julien,
> > Hello Ivan,
> >
> > > On Thu, Jun 02, 2016 at 12:41:02PM +0100, Julien Grall wrote:
> > > > Which compiler led to use a data abort? And where was the data
> > > > abort? In Xen or the guest?
> > > When I compile app directly on ODROID I used:
> > > arm-linux-gnueabihf
> > > gcc version 4.8.4 (Ubuntu/Linaro 4.8.4-2ubuntu1~14.04.1)
> > >
> > > HVC instruction works form assembler, but when I call it from main, for
> > > example:
> > > HYPERVISOR_console_io (HYPERCALL_WRITE, SYSTEM_UP_LEN, SYSTEM_UP_MSG);
> > > then I get this in xl dmesg:
> > > traps.c:2450:d2v0 HSR=0x90000046 pc=0x40008250 gva=0 gpa=0000000000000000
> > To be honest this looks like a latent issue in your app rather than
> > a bug in the compiler.
> >
> > I would try to find which instruction is causing the data abort.
> > Also is your app running with page table and cache enabled?
> Page table and cache are related to MMU, right? I didn't initialize MMU
> so far.
All the memory buffer passed to the hypercall should be cacheable (see 
xen/include/public/asm-arm.h for more details). I.e the MMU should be 
enabled.
Otherwise, the behavior is unreliable because the memory attribute will 
be different in Xen and the guest. Xen is mapping the region cacheable.
Regards,

--
Julien Grall

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