The starting point for this series was the intention to interleave the register clearing with register PUSH or MOV instructions, in order to minimize the cost of the additional instructions required for the register clearing. While at it, I noticed that a couple of macros in arch/x86/entry/calling.h are unused and can be cleaned up.
Based on a preliminary version of this patch,[*] Linus suggested to merge further codepaths and to use PUSH instead of MOV, as this should be faster on newer CPUs. [*] http://lkml.kernel.org/r/20180206212546.ga2...@light.dominikbrodowski.net and http://lkml.kernel.org/r/20180206213202.gb2...@light.dominikbrodowski.net NOTE / WARNING: Please be *extremely* stringent in reviewing these patches, *especially* concerning patch 6/7 (x86/entry: get rid of ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS). Dominik Brodowski (7): x86/entry: merge SAVE_C_REGS and SAVE_EXTRA_REGS, remove unused extensions x86/entry: merge POP_C_REGS and POP_EXTRA_REGS x86/entry: interleave XOR register clearing with PUSH instructions x86/entry: introduce PUSH_AND_CLEAN_REGS x86/entry: use PUSH_AND_CLEAN_REGS in more cases x86/entry: get rid of ALLOC_PT_GPREGS_ON_STACK and SAVE_AND_CLEAR_REGS x86/entry: indent PUSH_AND_CLEAR_REGS and POP_REGS properly arch/x86/entry/calling.h | 118 ++++++++++++++++++---------------------------- arch/x86/entry/entry_64.S | 104 +++++++--------------------------------- 2 files changed, 62 insertions(+), 160 deletions(-) -- 2.16.1
