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

[Quentin Perret]

On Tuesday 02 Feb 2021 at 10:00:29 (+0000), Will Deacon wrote:
> On Tue, Feb 02, 2021 at 09:57:36AM +0000, Quentin Perret wrote:
> > 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 <qperret at google.com>
> > > > ---
> > > >  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?
> 
> We wouldn't necessarily have to report anything, but having the return value
> of these functions be based off the generic checks would be great if we can
> do it (i.e. we'd avoid corrupting the list).

Ah, I see what you mean. Happy to have a go a it, there are a few other
small things that make that it a bit annoying e.g. CHECK_DATA_CORRUPTION
is unconditionally defined in bug.h, and I'll need to stub EXPORT_SYMBOL
as well, which may both require changing core files, but maybe that's
fine. And if that is too painful I think it would make sense to keep
this a separate and self-contained series which would be a nice
incremental improvement over the simple approach I have here :)

Cheers,
Quentin