On Tue, 19 Dec 2017 14:44:51 +1100 Alexey Kardashevskiy <a...@ozlabs.ru> wrote:
> On 18/12/17 16:02, Alex Williamson wrote: > > Add one more layer to our stack of MemoryRegions, this base region > > allows us to register BARs independently of the vfio region or to > > extend the size of BARs which do map to a region. This will be > > useful when we want hypervisor defined BARs or sections of BARs, > > for purposes such as relocating MSI-X emulation. We therefore call > > msix_init() based on this new base MemoryRegion, while the quirks, > > which only modify regions still operate on those sub-MemoryRegions. > > > Looks ok, one worry though - the default config produces this: > > > memory-region: p...@800000020000000.mmio > 0000000000000000-ffffffffffffffff (prio 0, i/o): p...@800000020000000.mmio > 0000210000000000-000021000000ffff (prio 1, i/o): 0001:03:00.0 base BAR 1 > 0000210000000000-000021000000ffff (prio 0, i/o): 0001:03:00.0 BAR 1 > 000021000000e000-000021000000e5ff (prio 0, i/o): msix-table > 000021000000f000-000021000000f00f (prio 0, i/o): msix-pba [disabled] > 0000210000040000-000021000007ffff (prio 1, i/o): 0001:03:00.0 base BAR 3 > 0000210000040000-000021000007ffff (prio 0, i/o): 0001:03:00.0 BAR 3 > 0000210000040000-000021000007ffff (prio 0, ramd): 0001:03:00.0 BAR > 3 mmaps[0] > > > Where "BAR 1" and "msix-table" overlap. It resolves correctly: > > > FlatView #1 > AS "memory", root: system > AS "cpu-memory", root: system > Root memory region: system > 0000000000000000-000000007fffffff (prio 0, ram): ppc_spapr.ram > 0000210000000000-000021000000dfff (prio 0, i/o): 0001:03:00.0 BAR 1 > 000021000000e000-000021000000e5ff (prio 0, i/o): msix-table > 000021000000e600-000021000000ffff (prio 0, i/o): 0001:03:00.0 BAR 1 > @000000000000e600 > 0000210000040000-000021000007ffff (prio 0, ramd): 0001:03:00.0 BAR 3 > mmaps[0] > > > but this looks like an accident - should not we raise the msix-table > priority or lower the BAR1 priority (to -1)? I was worried about this too, but the way I read the code is that the last registered subregion with the same priority wins. Therefore so long as msix_init() is called after we layer anything else onto the base BAR MemoryRegion that might interfere with it, everything should work correctly. It certainly might make sense for msix_init() to add subregions with a higher priority, but then you immediately get into the road block of what priority should it use, which is a bit of a rat hole since we can make it work as-is with proper ordering. Thanks, Alex
