[RFC 00/10] x86 TLB flush cleanups, moving toward PCID support

Andy Lutomirski
2017-05-07T22:06:55Z

As I've been working on polishing my PCID code, a major problem I've
encountered is that there are too many x86 TLB flushing code paths and
that they have too many inconsequential differences. The result was
that earlier versions of the PCID code were a colossal mess and very
difficult to understand.

This series goes a long way toward cleaning up the mess. With all the
patches applied, there is a single function that contains the meat of
the code to flush the TLB on a given CPU, and all the tlb flushing
APIs call it for both local and remote CPUs.

This series should only adversely affect the kernel in a couple of
minor ways:

- It makes smp_mb() unconditional when flushing TLBs. We used to
use the TLB flush itself to mostly avoid smp_mb() on the initiating
CPU.

- On UP kernels, we lose the dubious optimization of inlining nerfed
variants of all the TLB flush APIs. This bloats the kernel a tiny
bit, although it should increase performance, since the SMP
versions were better.

Patch 10 in here is a little bit off topic. It's a cleanup that's
also needed before PCID can go in, but it's not directly about
TLB flushing.

Thoughts?

This applies to tip:x86/mm. You can see it fully applied here:

https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/commit/?h=x86/tlbflush_cleanup&id=59ea83a0a78025439e3d15e09b693846fa1f4770

Andy Lutomirski (10):
x86/mm: Reimplement flush_tlb_page() using flush_tlb_mm_range()
x86/mm: Reduce indentation in flush_tlb_func()
x86/mm: Make the batched unmap TLB flush API more generic
x86/mm: Pass flush_tlb_info to flush_tlb_others() etc
x86/mm: Change the leave_mm() condition for local TLB flushes
x86/mm: Refactor flush_tlb_mm_range() to merge local and remote cases
x86/mm: Use new merged flush logic in arch_tlbbatch_flush()
x86/mm: Remove the UP tlbflush code; always use the formerly SMP code
x86/mm: Rework lazy TLB to track the actual loaded mm
x86,kvm: Teach KVM's VMX code that CR3 isn't a constant

arch/x86/Kconfig | 2 +-
arch/x86/events/core.c | 3 +-
arch/x86/include/asm/hardirq.h | 2 +-
arch/x86/include/asm/mmu.h | 6 -
arch/x86/include/asm/mmu_context.h | 21 +-
arch/x86/include/asm/paravirt.h | 6 +-
arch/x86/include/asm/paravirt_types.h | 5 +-
arch/x86/include/asm/tlbbatch.h | 14 ++
arch/x86/include/asm/tlbflush.h | 116 +++------
arch/x86/include/asm/uv/uv.h | 9 +-
arch/x86/kernel/ldt.c | 5 +-
arch/x86/kvm/vmx.c | 21 +-
arch/x86/mm/init.c | 4 +-
arch/x86/mm/tlb.c | 429 +++++++++++++++-------------------
arch/x86/platform/uv/tlb_uv.c | 8 +-
arch/x86/xen/mmu.c | 61 +++--
include/linux/mm_types_task.h | 15 +-
mm/rmap.c | 15 +-
18 files changed, 334 insertions(+), 408 deletions(-)
create mode 100644 arch/x86/include/asm/tlbbatch.h

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2.9.3