[lkml]   [2018]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [RFC 0/4] Virtio uses DMA API for all devices
On Sun, Aug 05, 2018 at 03:09:55AM +0300, Michael S. Tsirkin wrote:
> So in this case however I'm not sure what exactly do we want to add. It
> seems that from point of view of the device, there is nothing special -
> it just gets a PA and writes there. It also seems that guest does not
> need to get any info from the device either. Instead guest itself needs
> device to DMA into specific addresses, for its own reasons.
> It seems that the fact that within guest it's implemented using a bounce
> buffer and that it's easiest to do by switching virtio to use the DMA API
> isn't something virtio spec concerns itself with.

And that is exactly what we added bus_dma_mask for - the case where
the device itself has not limitation (or a bigger limitation), but
the platform limits the accessible dma ranges. One typical case is
a PCIe root port that is only connected to the CPU through an
interconnect that is limited to 32 address bits for example.

 \ /
  Last update: 2018-08-05 09:25    [W:0.104 / U:5.216 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site