Revision bd0e162d0312aa95e8b85ba883efddebf27be121 authored by Linus Torvalds on 31 May 2012, 19:09:07 UTC, committed by Linus Torvalds on 31 May 2012, 19:09:07 UTC
Pull two small kvm fixes from Avi Kivity: "A build fix for non-kvm archs and a transparent hugepage refcount bugfix on hosts with 4M pages." * git://git.kernel.org/pub/scm/virt/kvm/kvm: KVM: Export asm-generic/kvm_para.h KVM: MMU: fix huge page adapted on non-PAE host
swp_emulation
Software emulation of deprecated SWP instruction (CONFIG_SWP_EMULATE)
---------------------------------------------------------------------
ARMv6 architecture deprecates use of the SWP/SWPB instructions, and recommeds
moving to the load-locked/store-conditional instructions LDREX and STREX.
ARMv7 multiprocessing extensions introduce the ability to disable these
instructions, triggering an undefined instruction exception when executed.
Trapped instructions are emulated using an LDREX/STREX or LDREXB/STREXB
sequence. If a memory access fault (an abort) occurs, a segmentation fault is
signalled to the triggering process.
/proc/cpu/swp_emulation holds some statistics/information, including the PID of
the last process to trigger the emulation to be invocated. For example:
---
Emulated SWP: 12
Emulated SWPB: 0
Aborted SWP{B}: 1
Last process: 314
---
NOTE: when accessing uncached shared regions, LDREX/STREX rely on an external
transaction monitoring block called a global monitor to maintain update
atomicity. If your system does not implement a global monitor, this option can
cause programs that perform SWP operations to uncached memory to deadlock, as
the STREX operation will always fail.
Computing file changes ...
