RFC x86/mm: PCID and INVPCID

Here's my PCID and INVPCID work-in-progress. It seems to work well enough to play with it. (That is, I'm not aware of anything wrong with it, although it may eat your data.)

PCID and INVPCID use are orthogonal here. INVPCID is a straightforward speedup for global TLB flushes. Other than that, I don't use INVPCID at all, since it seems slower than just manipulating CR3 carefully, at least on my Skylake laptop.

Please play around and suggest (and run?) good benchmarks. It seems to save around 100ns on cross-process context switches for me. Unfortunately, we suck at context switches in general, so this is, at best, a little over a 10% speedup. Most of the time is spent in the scheduler, not in arch code.

Andy Lutomirski (13):
x86/paravirt: Turn KASAN off for parvirt.o
x86/mm: Add INVPCID helpers
x86/mm: Add a noinvpcid option to turn off INVPCID x86/mm: If INVPCID is available, use it to flush global mappings x86/mm: Add barriers and document switch_mm-vs-flush synchronization x86/mm: Disable PCID on 32-bit kernels
x86/mm: Add nopcid to turn off PCID
x86/mm: Teach CR3 readers about PCID
x86/mm: Disable interrupts when flushing the TLB using CR3 x86/mm: Factor out remote TLB flushing
x86/mm: Build arch/x86/mm/tlb.c even on !SMP
x86/mm: Uninline switch_mm
x86/mm: Try to preserve old TLB entries using PCID

 Documentation/kernel-parameters.txt      |   4 +
 arch/x86/include/asm/disabled-features.h |   4 +-
 arch/x86/include/asm/mmu.h               |   7 +-
 arch/x86/include/asm/mmu_context.h       |  62 +-----
 arch/x86/include/asm/tlbflush.h          |  86 ++++++++
 arch/x86/kernel/Makefile                 |   1 +
 arch/x86/kernel/cpu/bugs.c               |   6 +
 arch/x86/kernel/cpu/common.c             |  38 ++++
 arch/x86/kernel/head64.c                 |   3 +-
 arch/x86/kernel/ldt.c                    |   2 +
 arch/x86/kernel/process_64.c             |   2 +
 arch/x86/mm/Makefile                     |   3 +-
 arch/x86/mm/fault.c                      |   8 +-
 arch/x86/mm/tlb.c                        | 324 +++++++++++++++++++++++++++++--
 14 files changed, 467 insertions(+), 83 deletions(-)

2.5.0

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