Subject: Re: [RFC PATCH v2 11/26] KVM: arm64: Stub CONFIG_DEBUG_LIST at Hyp

From: Quentin Perret <[email-masked]>
Date: Tue, 2 Feb 2021 09:57:36 +0000

On Monday 01 Feb 2021 at 19:06:20 (+0000), Will Deacon wrote:
> On Fri, Jan 08, 2021 at 12:15:09PM +0000, Quentin Perret wrote:
> > In order to use the kernel list library at EL2, introduce stubs for the
> > CONFIG_DEBUG_LIST out-of-lines calls.
> > 
> > Signed-off-by: Quentin Perret <[email-masked]>
> > ---
> >  arch/arm64/kvm/hyp/nvhe/Makefile |  2 +-
> >  arch/arm64/kvm/hyp/nvhe/stub.c   | 22 ++++++++++++++++++++++
> >  2 files changed, 23 insertions(+), 1 deletion(-)
> >  create mode 100644 arch/arm64/kvm/hyp/nvhe/stub.c
> > 
> > diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile b/arch/arm64/kvm/hyp/nvhe/Makefile
> > index 1fc0684a7678..33bd381d8f73 100644
> > --- a/arch/arm64/kvm/hyp/nvhe/Makefile
> > +++ b/arch/arm64/kvm/hyp/nvhe/Makefile
> > @@ -10,7 +10,7 @@ lib-objs := clear_page.o copy_page.o memcpy.o memset.o
> >  lib-objs := $(addprefix ../../../lib/, $(lib-objs))
> >  
> >  obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o host.o \
> > -	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o
> > +	 hyp-main.o hyp-smp.o psci-relay.o early_alloc.o stub.o
> >  obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o ../entry.o \
> >  	 ../fpsimd.o ../hyp-entry.o ../exception.o
> >  obj-y += $(lib-objs)
> > diff --git a/arch/arm64/kvm/hyp/nvhe/stub.c b/arch/arm64/kvm/hyp/nvhe/stub.c
> > new file mode 100644
> > index 000000000000..c0aa6bbfd79d
> > --- /dev/null
> > +++ b/arch/arm64/kvm/hyp/nvhe/stub.c
> > @@ -0,0 +1,22 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Stubs for out-of-line function calls caused by re-using kernel
> > + * infrastructure at EL2.
> > + *
> > + * Copyright (C) 2020 - Google LLC
> > + */
> > +
> > +#include <linux/list.h>
> > +
> > +#ifdef CONFIG_DEBUG_LIST
> > +bool __list_add_valid(struct list_head *new, struct list_head *prev,
> > +		      struct list_head *next)
> > +{
> > +		return true;
> > +}
> > +
> > +bool __list_del_entry_valid(struct list_head *entry)
> > +{
> > +		return true;
> > +}
> > +#endif
> 
> Can we get away with defining our own CHECK_DATA_CORRUPTION macro instead?

Yes I think eventually it'd be nice to get there, but that has other
implications (e.g. how do you report something in dmesg from EL2?) so
perhaps we can keep that a separate series?

Cheers,
Quentin

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