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| author | Mark Rutland <mark.rutland@arm.com> | 2016-09-08 12:55:34 (GMT) |
|---|---|---|
| committer | Will Deacon <will.deacon@arm.com> | 2016-09-09 10:40:39 (GMT) |
| commit | 7aff4a2dd3db4e519c636f43aa863078e3b30d0f (patch) | |
| tree | 04647ea7e4ff76116cdfd25cd63d83436e388cb9 | |
| parent | ee5e41b5f21a5438664effce1ba5bdd11e03ee24 (diff) | |
| download | linux-7aff4a2dd3db4e519c636f43aa863078e3b30d0f.tar.xz | |
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>
| -rw-r--r-- | arch/arm64/include/asm/sysreg.h | 8 |
1 files changed, 6 insertions, 2 deletions
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 |