linux-kernel - Re: [PATCH v4 11/34] KVM: arm64: Stub CONFIG_DEBUG

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Message-ID: <20210311161127.GB31206@willie-the-truck>
Date:   Thu, 11 Mar 2021 16:11:28 +0000
From:   Will Deacon <will@...nel.org>
To:     Quentin Perret <qperret@...gle.com>
Cc:     catalin.marinas@....com, maz@...nel.org, james.morse@....com,
        julien.thierry.kdev@...il.com, suzuki.poulose@....com,
        android-kvm@...gle.com, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org, tabba@...gle.com,
        mark.rutland@....com, dbrazdil@...gle.com, mate.toth-pal@....com,
        seanjc@...gle.com, robh+dt@...nel.org, ardb@...nel.org
Subject: Re: [PATCH v4 11/34] KVM: arm64: Stub CONFIG_DEBUG_LIST at Hyp

On Wed, Mar 10, 2021 at 05:57:28PM +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@...gle.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 24ff99e2eac5..144da72ad510 100644
> --- a/arch/arm64/kvm/hyp/nvhe/Makefile
> +++ b/arch/arm64/kvm/hyp/nvhe/Makefile
> @@ -13,7 +13,7 @@ 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

This isn't any worse than disabling DEBUG_LIST for the EL2 object, so as
an initial implementation:

Acked-by: Will Deacon <will@...nel.org>

but we really should have the debug list checks on (probably
unconditionally) for the EL2 code in my opinion.

Will