[PATCH 6.1.y] KVM: arm64: sys_regs: disable -Wuninitialized-const-pointer warning

[PATCH 6.1.y] KVM: arm64: sys_regs: disable -Wuninitialized-const-pointer warning

[Justin Stitt]

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:2978:23: warning: variable 'clidr' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
|   2978 |         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@vger.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@google.com>
---
I've sent a similar patch for 5.15.
---
 arch/arm64/kvm/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 5e33c2d4645a..5fdb5331bfad 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -24,6 +24,9 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
 
 kvm-$(CONFIG_HW_PERF_EVENTS)  += pmu-emul.o pmu.o
 
+# Work around a false positive Clang 22 -Wuninitialized-const-pointer warning
+CFLAGS_sys_regs.o := $(call cc-disable-warning, uninitialized-const-pointer)
+
 always-y := hyp_constants.h hyp-constants.s
 
 define rule_gen_hyp_constants

---
base-commit: 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
change-id: 20250728-stable-disable-unit-ptr-warn-281fee82539c

Best regards,
--
Justin Stitt <justinstitt@google.com>

Re: [PATCH 6.1.y] KVM: arm64: sys_regs: disable -Wuninitialized-const-pointer warning

[Nathan Chancellor]

On Mon, Jul 28, 2025 at 02:07:36PM -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:2978:23: warning: variable 'clidr' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer]
> |   2978 |         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@vger.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@google.com>
> ---

Yes, I think this is an appropriate way to address this for stable.

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

> ---
>  arch/arm64/kvm/Makefile | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 5e33c2d4645a..5fdb5331bfad 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -24,6 +24,9 @@ kvm-y += arm.o mmu.o mmio.o psci.o hypercalls.o pvtime.o \
>  
>  kvm-$(CONFIG_HW_PERF_EVENTS)  += pmu-emul.o pmu.o
>  
> +# Work around a false positive Clang 22 -Wuninitialized-const-pointer warning
> +CFLAGS_sys_regs.o := $(call cc-disable-warning, uninitialized-const-pointer)
> +
>  always-y := hyp_constants.h hyp-constants.s
>  
>  define rule_gen_hyp_constants
> 
> ---
> base-commit: 830b3c68c1fb1e9176028d02ef86f3cf76aa2476
> change-id: 20250728-stable-disable-unit-ptr-warn-281fee82539c
> 
> Best regards,
> --
> Justin Stitt <justinstitt@google.com>
>