A common pattern is to conditionally update ZCR_ELx in order to avoid the "self-synchronizing" effect that writing to this register has.
Let's provide an accessor that does exactly this. Signed-off-by: Marc Zyngier <[email protected]> --- arch/arm64/include/asm/fpsimd.h | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index bec5f14b622a..05c9c55768b8 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -130,6 +130,15 @@ static inline void sve_user_enable(void) sysreg_clear_set(cpacr_el1, 0, CPACR_EL1_ZEN_EL0EN); } +#define sve_cond_update_zcr_vq(val, reg) \ + do { \ + u64 __zcr = read_sysreg_s((reg)); \ + u64 __new = __zcr & ~ZCR_ELx_LEN_MASK; \ + __new |= (val) & ZCR_ELx_LEN_MASK; \ + if (__zcr != __new) \ + write_sysreg_s(__new, (reg)); \ + } while (0) + /* * Probing and setup functions. * Calls to these functions must be serialised with one another. -- 2.29.2 _______________________________________________ kvmarm mailing list [email protected] https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
