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Re: [PATCH v2] Avoid address_space_rw() with a constant is_write argumen

From: Philippe Mathieu-Daudé
Subject: Re: [PATCH v2] Avoid address_space_rw() with a constant is_write argument
Date: Thu, 20 Feb 2020 10:27:14 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1

On 2/18/20 1:56 PM, Philippe Mathieu-Daudé wrote:
On 2/18/20 12:24 PM, Peter Maydell wrote:
The address_space_rw() function allows either reads or writes
depending on the is_write argument passed to it; this is useful
when the direction of the access is determined programmatically
(as for instance when handling the KVM_EXIT_MMIO exit reason).
Under the hood it just calls either address_space_write() or

We also use it a lot with a constant is_write argument, though,
which has two issues:
  * when reading "address_space_rw(..., 1)" this is less
    immediately clear to the reader as being a write than
  * calling address_space_rw() bypasses the optimization
    in address_space_read() that fast-paths reads of a
    fixed length

This commit was produced with the included Coccinelle script

Script is "scripts/coccinelle/as_rw_const.cocci".

I plan to respin this patch (fixed) in a larger series.

Two lines in hw/net/dp8393x.c that Coccinelle produced that
were over 80 characters were re-wrapped by hand.

Signed-off-by: Peter Maydell <address@hidden>
I could break this down into separate patches by submaintainer,
but the patch is not that large and I would argue that it's
better for the project if we can try to avoid introducing too
much friction into the process of doing 'safe' tree-wide
minor refactorings.

v1->v2: put the coccinelle script in scripts/coccinelle rather
than just in the commit message.
  accel/kvm/kvm-all.c                  |  6 +--
  dma-helpers.c                        |  4 +-
  exec.c                               |  4 +-
  hw/dma/xlnx-zdma.c                   | 11 ++---
  hw/net/dp8393x.c                     | 68 ++++++++++++++--------------
  hw/net/i82596.c                      | 25 +++++-----
  hw/net/lasi_i82596.c                 |  5 +-
  hw/ppc/pnv_lpc.c                     |  8 ++--
  hw/s390x/css.c                       | 12 ++---
  qtest.c                              | 52 ++++++++++-----------
  target/i386/hvf/x86_mmu.c            | 12 ++---
  scripts/coccinelle/as_rw_const.cocci | 30 ++++++++++++
  12 files changed, 133 insertions(+), 104 deletions(-)
  create mode 100644 scripts/coccinelle/as_rw_const.cocci

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