From df8261a46e9614f92023bb575fad7873b9d77302 Mon Sep 17 00:00:00 2001 From: Kinsey Moore Date: Fri, 4 Mar 2022 13:47:40 -0600 Subject: cpu-supplement: Add note about device memory Add information about restricted use of device memory for ARM and AArch64. --- cpu-supplement/arm.rst | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'cpu-supplement/arm.rst') diff --git a/cpu-supplement/arm.rst b/cpu-supplement/arm.rst index ac9e8c6..b92e6d6 100644 --- a/cpu-supplement/arm.rst +++ b/cpu-supplement/arm.rst @@ -132,6 +132,12 @@ Memory Model A flat 32-bit memory model is supported. The board support package must take care of initializing the MMU if necessary. +Note that architecture variants which support unaligned accesses must not use +memcpy() or memset() on device memory as those functions are hand-optimized and +will take advantage of unaligned accesses where available. *As per ARM* +(https://developer.arm.com/documentation/ddi0406/c/Application-Level-Architecture/Application-Level-Memory-Model/Alignment-support/Unaligned-data-access-restrictions-in-ARMv7-and-ARMv6), +unaligned accesses are not permitted for device memory. + Interrupt Processing ==================== -- cgit v1.2.3