| Message ID | 1473339339-32334-2-git-send-email-mark.rutland@arm.com |
|---|---|
| State | Accepted |
| Commit | 7aff4a2dd3db4e519c636f43aa863078e3b30d0f |
| Headers | show |
diff --git a/arch/arm64/include/asm/sysreg.h b/arch/arm64/include/asm/sysreg.h index cc06794..39fed2e 100644 --- a/arch/arm64/include/asm/sysreg.h +++ b/arch/arm64/include/asm/sysreg.h @@ -273,10 +273,14 @@ static inline void config_sctlr_el1(u32 clear, u32 set) __val; \ }) +/* + * The "Z" constraint normally means a zero immediate, but when combined with + * the "%x0" template means XZR. + */ #define write_sysreg(v, r) do { \ u64 __val = (u64)v; \ - asm volatile("msr " __stringify(r) ", %0" \ - : : "r" (__val)); \ + asm volatile("msr " __stringify(r) ", %x0" \ + : : "rZ" (__val)); \ } while (0) #endif
Currently write_sysreg has to allocate a temporary register to write zero to a system register, which is unfortunate given that the MSR instruction accepts XZR as an operand. Allow XZR to be used when appropriate by fiddling with the assembly constraints. Signed-off-by: Mark Rutland <mark.rutland@arm.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Marc Zyngier <marc.zyngier@arm.com> Cc: Robin Murphy <robin.murphy@arm.com> Cc: Suzuki K Poulose <suzuki.poulose@arm.com> Cc: Will Deacon <will.deacon@arm.com> --- arch/arm64/include/asm/sysreg.h | 8 ++++++-- 1 file changed, 6 insertions(+), 2 deletions(-) -- 1.9.1 _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel