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Compilers only recognise that __val was initialised with a constant zero after constant propagation. With optimisation disabled, the fallback path therefore selects an arbitrary general-purpose register. This is incorrect for instructions such as GIC CDEOI, where Rt must be XZR rather than a register containing zero. Test the macro argument directly so that constant zero selects XZR regardless of the optimisation level. Fixes: e9ad390a4812 ("arm64/sysreg: Fix GIC CDEOI instruction encoding") Signed-off-by: Sascha Bischoff --- arch/arm64/include/asm/sysreg.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysre= g.h index 7aa08d59d4944..a80bede50f865 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -1204,7 +1204,7 @@ #define write_sysreg_s(v, r) do { \ u64 __val =3D (u64)(v); \ u32 __maybe_unused __check_r =3D (u32)(r); \ - if (__builtin_constant_p(__val) && __val =3D=3D 0) \ + if (__builtin_constant_p(v) && (u64)(v) =3D=3D 0) \ asm volatile(__msr_s(r, "xzr")); \ else \ asm volatile(__msr_s(r, "%x0") : : "r" (__val)); \ --=20 2.34.1