Module Name: src
Committed By: riastradh
Date: Mon Dec 2 08:33:52 UTC 2019
Modified Files:
src/sys/arch/x86/x86: bus_space.c
Log Message:
Use LFENCE/SFENCE/MFENCE in x86 bus_space_barrier.
These are needed for BUS_SPACE_MAP_PREFETCHABLE mappings. On x86,
these are WC-type memory regions, which means -- unlike normal
WB-type memory regions -- loads can be reordered with loads,
requiring LFENCE, and stores can be reordered with stores, requiring
SFENCE.
Reference: AMD64 Architecture Programmer's Manual, Volume 2: System
Programming, Sec. 7.4.1 `Memory Barrier Interaction with Memory
Types', Table 7-3 `Memory Access Ordering Rules'.
To generate a diff of this commit:
cvs rdiff -u -r1.41 -r1.42 src/sys/arch/x86/x86/bus_space.c
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
