On 05/21/2014 06:40 PM, Alexander Graf wrote: > > On 15.05.14 11:59, Alexey Kardashevskiy wrote: >> Currently SPAPR PHB keeps track of all allocated MSI/MISX interrupt as >> XICS used to be unable to reuse interrupts which becomes a problem for >> dynamic MSI reconfiguration which is happening on guest driver reload or >> PCI hot (un)plug. Another problem is that PHB has a limit of devices >> supporting MSI/MSIX (SPAPR_MSIX_MAX_DEVS=32) and there is no good reason >> for that. >> >> This makes use of new XICS ability to reuse interrupts. >> >> This removes cached MSI configuration from SPAPR PHB so the first IRQ number >> of a device is stored in MSI/MSIX config space so there is no need to store >> this anywhere else. From now on, SPAPR PHB only keeps flags telling what >> type >> of interrupt for which device it has configured in order to return error if >> (for example) MSIX was enabled and the guest is trying to disable MSI which >> it has not enabled. >> >> This removes a limit for the maximum number of MSIX-enabled devices per PHB, >> now XICS and PCI bus capacity are the only limitation. >> >> This changes migration stream as it fixes vmstate_spapr_pci_msi::name >> which was >> wrong since the beginning. >> >> This fixed traces to be more informative. >> >> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> >> --- >> >> In reality either MSIX or MSI is enabled, never both. So I could remove >> msi/msix >> bitmaps from this patch, would it make sense? > > Is this a hard requirement? Does a device have to choose between MSIX and > MSI or could it theoretically have both enabled? Is this a PCI limitation, > a PAPR/XICS limitation or just a limitation of your implementation?
My implementation does not have this limitation, I asked if I can simplify code by introducing one :) I cannot see any reason why PCI cannot have both MSI and MSIX enabled but it does not seem to be used by anyone => cannot debug and confirm. PAPR spec assumes that if the guest tries enabling MSIX when MSI is already enabled, this is a "change", not enabling both types. But it also says MSI and MSIX vector numbers are not shared. Hm. -- Alexey
