linux-kernel - Re: [PATCH 5.15.y] KVM: arm64: sys_regs: disable -Wuninitialized-const-pointer warning

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Message-ID: <20250806222624.GB1654483@ax162>
Date: Wed, 6 Aug 2025 15:26:24 -0700
From: Nathan Chancellor <nathan@...nel.org>
To: Justin Stitt <justinstitt@...gle.com>
Cc: Marc Zyngier <maz@...nel.org>, James Morse <james.morse@....com>,
	Alexandru Elisei <alexandru.elisei@....com>,
	Suzuki K Poulose <suzuki.poulose@....com>,
	Catalin Marinas <catalin.marinas@....com>,
	Will Deacon <will@...nel.org>,
	Nick Desaulniers <ndesaulniers@...gle.com>,
	Christopher Covington <cov@...eaurora.org>,
	linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu,
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev,
	stable@...r.kernel.org
Subject: Re: [PATCH 5.15.y] KVM: arm64: sys_regs: disable
 -Wuninitialized-const-pointer warning

On Mon, Jul 28, 2025 at 02:04:24PM -0700, Justin Stitt wrote:
> A new warning in Clang 22 [1] complains that @clidr passed to
> get_clidr_el1() is an uninitialized const pointer. get_clidr_el1()
> doesn't really care since it casts away the const-ness anyways -- it is
> a false positive.
> 
> |  ../arch/arm64/kvm/sys_regs.c:2838:23: warning: variable 'clidr' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
> |   2838 |         get_clidr_el1(NULL, &clidr); /* Ugly... */
> |        |                              ^~~~~
> 
> Disable this warning for sys_regs.o with an iron fist as it doesn't make
> sense to waste maintainer's time or potentially break builds by
> backporting large changelists from 6.2+.
> 
> This patch isn't needed for anything past 6.1 as this code section was
> reworked in Commit 7af0c2534f4c ("KVM: arm64: Normalize cache
> configuration").
> 
> Cc: stable@...r.kernel.org
> Fixes: 7c8c5e6a9101e ("arm64: KVM: system register handling")
> Link: https://github.com/llvm/llvm-project/commit/00dacf8c22f065cb52efb14cd091d441f19b319e [1]
> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> ---

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

> ---
>  arch/arm64/kvm/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 989bb5dad2c8..109cca425d3e 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -25,3 +25,6 @@ kvm-y := $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o \
>  	 vgic/vgic-its.o vgic/vgic-debug.o
>  
>  kvm-$(CONFIG_HW_PERF_EVENTS)  += pmu-emul.o
> +
> +# Work around a false positive Clang 22 -Wuninitialized-const-pointer warning
> +CFLAGS_sys_regs.o := $(call cc-disable-warning, uninitialized-const-pointer)
> 
> ---
> base-commit: 8bb7eca972ad531c9b149c0a51ab43a417385813
> change-id: 20250728-b4-stable-disable-uninit-ptr-warn-5-15-c0c9db3df206
> 
> Best regards,
> --
> Justin Stitt <justinstitt@...gle.com>
> 
>