Commit 7aff4a2d authored Sep 08, 2016 by Mark Rutland Committed by Will Deacon Sep 09, 2016

arm64: sysreg: allow write_sysreg to use XZR



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.

Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Cc: Suzuki K Poulose <suzuki.poulose@arm.com>
Reviewed-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>

parent ee5e41b5

arch/arm64/include/asm/sysreg.h

+6 −2

Original line number	Diff line number	Diff line
		@@ -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