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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Mon, 20 Aug 2018, Julien Grall wrote:
> 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.

OK

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