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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: Nicholas Piggin <npiggin@gmail.com> [mpe: Fixup BE by using DOTSYM for idle_return_gpr_loss call] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> |
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.