linux-kernel - [PATCH 6.1.y RESEND v2] KVM: arm64: sys_regs: disable -Wuninitialized-const-pointer warning

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Message-ID: <20251205-stable-disable-unit-ptr-warn-v2-1-cec53a8f736b@google.com>
Date: Fri, 05 Dec 2025 14:51:41 -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 6.1.y RESEND v2] 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.

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

Disable this warning for sys_regs.o instead of backporting the patches
from 6.2+ that modified this code area.

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>
---
Changes in v2:
- disable warning for TU instead of initialising the struct
- update commit message
- Link to v1: https://lore.kernel.org/all/20250724-b4-clidr-unint-const-ptr-v1-1-67c4d620b6b6@google.com/
- Link to v1 resend (sent wrong diff, thanks Nathan): https://lore.kernel.org/all/20251204-b4-clidr-unint-const-ptr-v1-1-95161315ad92@google.com/
---
 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@...gle.com>