[Qemu-devel] Re: [kvm-devel] [PATCH 2/6] PCI DMA API

[Anthony Liguori]

Avi Kivity wrote:
> Anthony Liguori wrote:
> > This patch introduces a PCI DMA API and some generic code to support 
> > other DMA
> > APIs.  Two types are introduced: PhysIOVector and IOVector.  A DMA API
> > maps a PhysIOVector, which is composed of target_phys_addr_t, into an 
> > IOVector,
> > which is composed of void *.
> >
> > This enables zero-copy IO to be preformed without introducing 
> > assumptions of
> > phys_ram_base.  This API is at the PCI device level to enable support of
> > per-device IOMMU remapping.
> >
> >
> > +
> > +typedef struct IOVector
> > +{
> > +    int num;
> > +    struct IOVectorElement {
> > +    void *base;
> > +    size_t len;
> > +    } sg[0];
> > +} IOVector;
> > +
> >   
>
> Can we use 'struct iovec' for the element type (with accessors for 
> setting base+len, and reading base or len, so we can substitute the 
> Windows version for that platform)? That will allow using the vector 
> without additional translation or casts.

If we switch to PhysIOVector => PhysIOVector, then the IO infrastructure 
can convert it to whatever it wants (including a struct iovec).

Regards,

Anthony Liguori