On Wed, Jan 14, 2015 at 11:23:10AM -0600, Michael Roth wrote: > Quoting David Gibson (2015-01-13 20:33:39) > > pseries guests can have large numbers of PCI host bridges. To avoid the > > user having to specify a number of different configuration values for every > > one, the device supports an "index" property which is a shorthand setting > > the various window and configuration addresses from a predefined sensible > > set. > > > > There are some problems with the details at present: > > * The "index" propery is signed, but negative values will create PCI > > windows below where we expect, potentially colliding with other devices > > * No limit is imposed on the "index" property and large values can > > translate to extremely large window addresses. With PCI passthrough in > > particular this can mean we exceed various mapping and physical address > > limits causing the guest host bridge to not work in strange ways. > > > > This patch addresses this, by making "index" unsigned, and imposing a > > limit. Currently the limit allows indices from 0..255 which is probably > > enough host bridges for the time being. It's fairly easy to extend if > > we discover we need more. > > > > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au> > > I think the limit makes sense, but since the check isn't triggered in cases > where 'index' isn't specified and '[io,mem]_win_[size,offset]' are set > explicitly, maybe it makes sense to sanity-check the final calculation for > those values as well? We could actually drop the index limit in that case > (if we decided we wanted to). > > But I think it's okay to assume such users know what they're doing in the > meantime, so:
Yeah, that was my assumption, that if you're explicitly setting the
windows, then you know what you're doing.
> Reviewed-by: Michael Roth <mdr...@linux.vnet.ibm.com>
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David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
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