On Wednesday 30 June 2010 09:16:23 pm Alex Williamson wrote:
> On Tue, 2010-06-08 at 14:21 -0700, Tom Lyon wrote:
> > +int vfio_dma_unmap_dm(struct vfio_listener *listener, struct vfio_dma_map *dmp)
> > +{
> > + unsigned long start, npage;
> > + struct dma_map_page *mlp;
> > + struct list_head *pos, *pos2;
> > + int ret;
> > +
> > + start = dmp->vaddr & ~PAGE_SIZE;
> > + npage = dmp->size >> PAGE_SHIFT;
> > +
> > + ret = -ENXIO;
> > + mutex_lock(&listener->vdev->dgate);
> > + list_for_each_safe(pos, pos2, &listener->dm_list) {
> > + mlp = list_entry(pos, struct dma_map_page, list);
> > + if (dmp->vaddr != mlp->vaddr || mlp->npage != npage)
> > + continue;
> > + ret = 0;
> > + vfio_dma_unmap(listener, mlp);
> > + break;
> > + }
>
> Hi Tom,
>
> Shouldn't we be matching the mlp based on daddr instead of vaddr? We
> can have multiple dma address pointing at the same virtual address, so
> dma address is the unique element. I'm also nervous about this dm_list.
> For qemu device assignment, we're potentially statically mapping many GB
> of iova space. It seems like this could get incredibly bloated and
> slow. Thanks,
>
> Alex
In weird circumstances, differing user vaddrs could reolve to the same physical address,
so the uniqueness of any mapping is the <vaddr,len>.
Yes, a linear list is slow, but does qemu need a lot of mappings, or just big ones?
>
>
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