Re: [Xen-devel] [PATCH 15/15] xen/arm: traps: Move the implementation of GUEST_BUG_ON in traps.h

[Julien Grall <julien.grall@xxxxxxxxxx>]

Hi Stefano,

On Thu, 16 Aug 2018, 19:17 Stefano Stabellini, <sstabellini@xxxxxxxxxx> wrote:

On Thu, 16 Aug 2018, Julien Grall wrote:
> Hi Stefano,
>
> On 08/14/2018 10:43 PM, Stefano Stabellini wrote:
> > On Mon, 16 Jul 2018, Julien Grall wrote:
> > > GUEST_BUG_ON may be used in other files doing guest emulation.
> > >
> > > Signed-off-by: Julien Grall <julien.grall@xxxxxxxxxx>
> >
> > Given that GUEST_BUG_ON is not actually used in any other files in this
> > patch series, I assume you are referring to one of your future series?
>
> It is going to be used later. However, I don't really refer to any series in
> particular. It is just that this macros could be helpful in any emulation code
> to catch what we think is a invalid architectural behavior.

It is only that a concrete use-case helps. The idea of moving
GUEST_BUG_ON is good, but where to? For instance, wouldn't it be better
to move it to guest_access.h? I am just trying to point to an existing
header which is more widely used across the emulators (vpl011,
vgic-v3-its.c, hvm.c, ...)

Definitely not in guest_access.h or any wider in includes. If you look at the implementation and documentation, it will crash the hypervisor because the goal is to catch hardware bug or misunderstanding of the spec. This is not meant to be used in emulation. We should not crash the guest/hypervisor in bad behavior but inject an exception.

So trap.h is the best places for it as hardware trap are now split accros multiples files.

Cheers,

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