On Thursday 01 July 2010 08:48:41 am Alex Williamson wrote: > On Thu, 2010-07-01 at 18:31 +0300, Michael S. Tsirkin wrote: > > On Thu, Jul 01, 2010 at 09:29:04AM -0600, Alex Williamson wrote: > > > On Tue, 2010-06-08 at 14:21 -0700, Tom Lyon wrote: > > > > +The VFIO_DMA_MASK ioctl is used to set the maximum permissible DMA address > > > > +(device dependent). It takes a single unsigned 64 bit integer as an argument. > > > > +This call also has the side effect of enabling PCI bus mastership. > > > > > > Hi Tom, > > > > > > This interface doesn't make sense for the MAP_IOVA user. Especially in > > > qemu, we have no idea what the DMA mask is for the device we're > > > assigning. It doesn't really matter though because the guest will use > > > bounce buffers internally once it loads the device specific drivers and > > > discovers the DMA mask. This only seems relevant if we're using a > > > DMA_MAP call that gets to pick the dmaaddr, so I'd propose we only make > > > this a required call for that interface, and create a separate ioctl for > > > actually enabling bus master. Thanks, > > > > > > Alex > > > > I expect there's no need for a separate ioctl to do this: > > you can do this by write to the control register. > > Nope, vfio only allows direct writes to the memory and io space bits of > the command register, all other bits are virtualized. I wonder if > that's necessary though since we require the device to be attached to an > iommu domain before we allow config space access. > I had already gotten rid of the mask setting & master mode ioctl. It was a remnant of using the dma_map_sg API which is no longer in there. And I tweaked the config stuff to allow writing the master bit. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
