Re: [PATCH] kvm: arm64: use BUG() instead of BUG_ON(1)

Nathan Chancellor
2025-08-07T15:59:18Z

On Thu, Aug 07, 2025 at 09:21:28AM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> The BUG_ON() macro adds a little bit of complexity over BUG(), and in
> some cases this ends up confusing the compiler's control flow analysis
> in a way that results in a warning. This one now shows up with clang-21:
>
> arch/arm64/kvm/vgic/vgic-mmio.c:1094:3: error: variable 'len' is used uninitialized whenever 'if' condition is false [-Werror,-Wsometimes-uninitialized]
> 1094 | BUG_ON(1);
>
> Change both instances of BUG_ON(1) to a plain BUG() in the arm64 kvm
> code, to avoid the false-positive warning.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

Yeah I had responded to a build report around this but I never followed
up on seeing if it got fixed.

https://lore.kernel.org/20250714171559.GA1364710@ax162/

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

> ---
> arch/arm64/kvm/hyp/nvhe/list_debug.c | 2 +-
> arch/arm64/kvm/vgic/vgic-mmio.c | 2 +-
> 2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp/nvhe/list_debug.c b/arch/arm64/kvm/hyp/nvhe/list_debug.c
> index 46a2d4f2b3c6..baa6260f88dc 100644
> --- a/arch/arm64/kvm/hyp/nvhe/list_debug.c
> +++ b/arch/arm64/kvm/hyp/nvhe/list_debug.c
> @@ -17,7 +17,7 @@ static inline __must_check bool nvhe_check_data_corruption(bool v)
> bool corruption = unlikely(condition); \
> if (corruption) { \
> if (IS_ENABLED(CONFIG_BUG_ON_DATA_CORRUPTION)) { \
> - BUG_ON(1); \
> + BUG(); \
> } else \
> WARN_ON(1); \
> } \
> diff --git a/arch/arm64/kvm/vgic/vgic-mmio.c b/arch/arm64/kvm/vgic/vgic-mmio.c
> index e416e433baff..a573b1f0c6cb 100644
> --- a/arch/arm64/kvm/vgic/vgic-mmio.c
> +++ b/arch/arm64/kvm/vgic/vgic-mmio.c
> @@ -1091,7 +1091,7 @@ int vgic_register_dist_iodev(struct kvm *kvm, gpa_t dist_base_address,
> len = vgic_v3_init_dist_iodev(io_device);
> break;
> default:
> - BUG_ON(1);
> + BUG();
> }
>
> io_device->base_addr = dist_base_address;
> --
> 2.39.5
>
>