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  1. 03 Jul, 2019 2 commits
    • Nicholas Piggin's avatar
      powerpc/64s/exception: sreset move trampoline ahead of common code · acc8da44
      Nicholas Piggin authored 
      Follow convention and move tramp ahead of common.
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      acc8da44
    • Nicholas Piggin's avatar
      powerpc/64s/exception: optimise system_reset for idle, clean up non-idle case · 0e10be2b
      Nicholas Piggin authored 
      The idle wake up code in the system reset interrupt is not very
optimal. There are two requirements: perform idle wake up quickly;
and save everything including CFAR for non-idle interrupts, with
no performance requirement.

The problem with placing the idle test in the middle of the handler
and using the normal handler code to save CFAR, is that it's quite
costly (e.g., mfcfar is serialising, speculative workarounds get
applied, SRR1 has to be reloaded, etc). It also prevents the standard
interrupt handler boilerplate being used.

This pain can be avoided by using a dedicated idle interrupt handler
at the start of the interrupt handler, which restores all registers
back to the way they were in case it was not an idle wake up. CFAR
is preserved without saving it before the non-idle case by making that
the fall-through, and idle is a taken branch.

Performance seems to be in the noise, but possibly around 0.5% faster,
the executed instructions certainly look better. The bigger benefit is
being able to drop in standard interrupt handlers after the idle code,
which helps with subsequent cleanup and consolidation.
Signed-off-by: default avatarNicholas Piggin <npiggin@gmail.com>
[mpe: Fixup BE by using DOTSYM for idle_return_gpr_loss call]
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
      0e10be2b
  3. 02 Jul, 2019 38 commits
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