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

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Message-ID: <20251204-b4-stable-disable-uninit-ptr-warn-5-15-v1-1-41212e2c6409@google.com>
Date: Thu, 04 Dec 2025 12:44:48 -0800
From: Justin Stitt <justinstitt@...gle.com>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
	Alexandru Elisei <alexandru.elisei@....com>, Joey Gouly <joey.gouly@....com>, 
	Suzuki K Poulose <suzuki.poulose@....com>, Catalin Marinas <catalin.marinas@....com>, 
	Zenghui Yu <yuzenghui@...wei.com>, Will Deacon <will@...nel.org>, 
	Nathan Chancellor <nathan@...nel.org>, Christopher Covington <cov@...eaurora.org>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.cs.columbia.edu, 
	linux-kernel@...r.kernel.org, llvm@...ts.linux.dev, stable@...r.kernel.org, 
	Justin Stitt <justinstitt@...gle.com>
Subject: [PATCH 5.15.y RESEND] KVM: arm64: sys_regs: disable
 -Wuninitialized-const-pointer warning

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... */
|        |                              ^~~~~

This patch isn't needed for anything past 6.1 as this code section was
reworked in Commit 7af0c2534f4c ("KVM: arm64: Normalize cache
configuration"). Since there is no upstream equivalent, this patch just
needs to be applied to 5.15.

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+.

Cc: stable@...r.kernel.org
Fixes: 7c8c5e6a9101e ("arm64: KVM: system register handling")
Link: https://github.com/llvm/llvm-project/commit/00dacf8c22f065cb52efb14cd091d441f19b319e [1]
Reviewed-by: Nathan Chancellor <nathan@...nel.org>
Signed-off-by: Justin Stitt <justinstitt@...gle.com>
---
Resending this with Nathan's RB tag, an updated commit log and better
recipients from checkpatch.pl.

I'm also sending a similar patch resend for 6.1.
---
 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>