Re: [PATCH v15 11/11] RFC: fw_cfg: do DMA read operation

[Marc-Andrà Lureau]

Hi

On Wed, Feb 28, 2018 at 4:48 PM, Michael S. Tsirkin <mst@xxxxxxxxxx> wrote:
> On Wed, Feb 28, 2018 at 04:41:51PM +0100, Marc-Andrà Lureau wrote:
>> I don't know if it's always safe to enable dma in read_raw(), how
>> could we know? Is there a check we could use to choose one or ther
>> other (and thus avoiding explicit dma/readfn argument)?
>
> I'm not sure - but does it really matter? Is anyone reading large files
> like this in production where speed matters?
> Why even bother with DMA?

The difference is quite significante for not so small files, as shown above.

And if they access the fw_cfg entries at boot time, or when starting
things etc, this may speed things up.