On 24.02.20 18:16, Christoph Hellwig wrote:
On Sat, Feb 22, 2020 at 02:07:58PM -0500, Michael S. Tsirkin wrote:
On Fri, Feb 21, 2020 at 03:33:40PM +0100, Halil Pasic wrote:
AFAIU you have a positive attitude towards the idea, that
!F_VIRTIO_PLATFORM implies 'no DMA API is used by virtio'
should be scrapped.
I would like to accomplish that without adverse effects to virtio-ccw
(because caring for virtio-ccw is a part of job description).
Regards,
Halil
It is possible, in theory. IIRC the main challenge is that DMA API
has overhead of indirect function calls even when all it
does it return back the PA without changes.
That overhead is gone now, the DMA direct calls are direct calls these
days.
Michael, would that mitigate your concerns to just always use the DMA
API? If not, wouldn't it make sense to benchmark and pinpoint Christoph
to paths that do slow things down, so we can finally move virtio into a
world where it doesn't bypass the kernel DMA infrastructure.
Alex
Amazon Development Center Germany GmbH
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10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
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