Messages in this thread | | | From | Tom Lyon <> | Subject | Re: [PATCH V2] VFIO driver: Non-privileged user level PCI drivers | Date | Wed, 30 Jun 2010 21:30:38 -0700 |
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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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