From mboxrd@z Thu Jan  1 00:00:00 1970
From: Christoffer Dall <christoffer.dall@linaro.org>
Subject: Re: [PATCH 6/7] KVM: arm64: re-factor hyp.S debug register code
Date: Tue, 2 Dec 2014 14:23:37 +0100
Message-ID: <20141202132337.GD545@cbox>
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Cc: kvm@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, marc.zyngier@arm.com,
	peter.maydell@linaro.org, agraf@suse.de, jan.kiszka@siemens.com,
	dahi@linux.vnet.ibm.com, r65777@freescale.com, bp@suse.de,
	pbonzini@redhat.com, Gleb Natapov <gleb@kernel.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>,
	open list <linux-kernel@vger.kernel.org>
To: Alex =?iso-8859-1?Q?Benn=E9e?= <alex.bennee@linaro.org>
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On Mon, Dec 01, 2014 at 11:52:44AM +0000, Alex Benn=E9e wrote:
>=20
> Christoffer Dall <christoffer.dall@linaro.org> writes:
>=20
> > On Tue, Nov 25, 2014 at 04:10:04PM +0000, Alex Benn=E9e wrote:
> >> This is a pre-cursor to sharing the code with the guest debug supp=
ort.
> >> This replaces the big macro that fishes data out of a fixed locati=
on
> >> with a more general helper macro to restore a set of debug registe=
rs. 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 bi=
t
> >> aligned (as they happen to be in the hyp ABI).
> >
> > can you enforce that somewhere?
>=20
> There is a comment in kvm_asm.h:
>=20
> /*
>  * 0 is reserved as an invalid value.
>  * Order *must* be kept in sync with the hyp switch code.
>  */
>=20
> But I'm not sure how to enforce it in assembly. Is there a #pragma or
> something I can use?
>=20

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=
=2E

-Christoffer