Re: [Qemu-devel] DMA active hw_error

[Peter Maydell]

On 28 December 2011 06:44, Richard Cole <address@hidden> wrote:
> I'll have to learn quite a bit more about QEMU and arm before I'll be
> able to contribute back any patches. I bought a beagle board today so
> that at least is a start, being able to compare QEMU to some real
> hardware.

There's no beagle board model in qemu at the moment (there is one
in qemu-linaro but it's taking me a long time to get the patches
cleaned up to submit upstream).

> Is there an issues list for QEMU.

There's https://bugs.launchpad.net/qemu, although it mostly contains
user-reported bugs rather than "things the developer community
knows are broken" issues.

> Does anyone use github features like
> being able to comment on particular sources lines or create issues
> refer to specific lines of code? That would seem a good way to track
> bugs discovered in the code.

The github mirror is a very recent development. I'm not sure
we want to have two different bug trackers on two different sites...

> A more broad question. Does anyone know why linux doesn't use the DMA?
> Is the DMA really old school (I grew up with an Amiga that was full of
> them), or is it just for portability, i.e that DMA differ from
> platform to platform too much?

The bugs we've been talking about are specific to the PL180 (which
is used on the ARM dev boards like vexpress, realview, etc).
Since these are only dev boards, I think nobody has ever got round
to implementing the DMA support in Linux for them. Other platforms
have different DMA setups and get more attention because there is
more interest in tuning the performance on those platforms. (eg OMAP
has its own DMA infrastructure, which is modelled in QEMU, because
the kernel uses it.)

-- PMM