Paul Mackerras 23316316c1 powerpc: Revert "Use the POWER8 Micro Partition Prefetch Engine in KVM HV on POWER8" ... This reverts commit 9678cdaae9 ("Use the POWER8 Micro Partition Prefetch Engine in KVM HV on POWER8") because the original commit had multiple, partly self-cancelling bugs, that could cause occasional memory corruption. In fact the logmpp instruction was incorrectly using register r0 as the source of the buffer address and operation code, and depending on what was in r0, it would either do nothing or corrupt the 64k page pointed to by r0. The logmpp instruction encoding and the operation code definitions could be corrected, but then there is the problem that there is no clearly defined way to know when the hardware has finished writing to the buffer. The original commit attempted to work around this by aborting the write-out before starting the prefetch, but this is ineffective in the case where the virtual core is now executing on a different physical core from the one where the write-out was initiated. These problems plus advice from the hardware designers not to use the function (since the measured performance improvement from using the feature was actually mostly negative), mean that reverting the code is the best option. Fixes: 9678cdaae9 ("Use the POWER8 Micro Partition Prefetch Engine in KVM HV on POWER8") Signed-off-by: Paul Mackerras <paulus@samba.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>		2015-10-21 20:50:30 +11:00
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asm	powerpc: Revert "Use the POWER8 Micro Partition Prefetch Engine in KVM HV on POWER8"	2015-10-21 20:50:30 +11:00
uapi/asm	powerpc: Wire up sys_membarrier()	2015-09-21 17:27:08 +10:00