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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

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
>> address_space_read_full().
>>
>> 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
>>     "address_space_write(...)"
>>   * 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
>> scripts/coccinelle/as-rw-const.patch.

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 <peter.maydell@linaro.org>
>> ---
>> 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