Re: [PATCH v2 0/3] Convert sparc devices to new ptimer API

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

On 10/21/19 3:43 PM, Peter Maydell wrote:
> This patchset converts the devices used by sparc machines to the new
> ptimer API.
> 
> Currently the ptimer design uses a QEMU bottom-half as its mechanism
> for calling back into the device model using the ptimer when the
> timer has expired.  Unfortunately this design is fatally flawed,
> because it means that there is a lag between the ptimer updating its
> own state and the device callback function updating device state, and
> guest accesses to device registers between the two can return
> inconsistent device state. This was reported as a bug in a specific
> timer device but it's a problem with the generic ptimer code:
> https://bugs.launchpad.net/qemu/+bug/1777777
> 
> The updates to the individual ptimer devices are straightforward:
> we need to add begin/commit calls around the various places that
> modify the ptimer state, and use the new ptimer_init() function
> to create the timer.
> 
> Changes v1->v2:
>   * patches 2 and 3 are the old 1 and 2 and have been reviewed
>   * patch 1 is new and removes a pointless NULL check; without
>     this we'd probably have got Coverity errors when patch 3
>     added a use of t->timer before the check for it being NULL
> 
> thanks
> --PMM
> 
> 
> MIME-Version: 1.0
> Content-Type: text/plain; charset=UTF-8
> Content-Transfer-Encoding: 8bit
> 
> *** BLURB HERE ***
> 
> Peter Maydell (3):
>    hw/timer/slavio_timer: Remove useless check for NULL t->timer
>    hw/timer/grlib_gptimer.c: Switch to transaction-based ptimer API
>    hw/timer/slavio_timer.c: Switch to transaction-based ptimer API

Nitpicking, maybe reorder the grlib_gptimer patch last:

   hw/timer/slavio_timer: Remove useless check for NULL t->timer
   hw/timer/slavio_timer.c: Switch to transaction-based ptimer API
   hw/timer/grlib_gptimer.c: Switch to transaction-based ptimer API