Re: [PATCH 6/7] KVM: arm64: re-factor hyp.S debug register code

From: Christoffer Dall
Date: Tue Dec 02 2014 - 08:22:59 EST

On Mon, Dec 01, 2014 at 11:52:44AM +0000, Alex Bennée wrote:
> Christoffer Dall <christoffer.dall@xxxxxxxxxx> writes:
> > On Tue, Nov 25, 2014 at 04:10:04PM +0000, Alex Bennée wrote:
> >> This is a pre-cursor to sharing the code with the guest debug support.
> >> This replaces the big macro that fishes data out of a fixed location
> >> with a more general helper macro to restore a set of debug registers. It
> >> uses macro substitution so it can be re-used for debug control and value
> >> registers. It does however rely on the debug registers being 64 bit
> >> aligned (as they happen to be in the hyp ABI).
> >
> > can you enforce that somewhere?
> There is a comment in kvm_asm.h:
> /*
> * 0 is reserved as an invalid value.
> * Order *must* be kept in sync with the hyp switch code.
> */
> But I'm not sure how to enforce it in assembly. Is there a #pragma or
> something I can use?

You can add a BUG_ON somewhere at runtime, but I wouldn't bother, you
can stick a note in that existing comment just so people don't change
the declaration of the registers to be 32-bit aligned or something else.

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