On Thu, Jul 15, 2010 at 07:45:06AM -0500, Anthony Liguori wrote: > > No. PCI devices should never call cpu_physical_memory*. > > PCI devices should call pci_memory*. > > ISA devices should call isa_memory*. > > All device memory accesses should go through their respective buses. > There can be multiple IOMMUs at different levels of the device > hierarchy. If you don't provide bus-level memory access functions that > chain through the hierarchy, it's extremely difficult to implement all > the necessary hooks to perform the translations at different places. > > Regards, > > Anthony Liguori > I liked Paul's initial approach more, at least if I understood him correctly. Basically I'm suggesting a single memory_* function that simply asks the bus for I/O and translation. Say you have something like this: + Bus 1 | ---- Memory 1 | ---+ Bus 2 bridge | ---- Memory 2 | ---+ Bus 3 bridge | ---- Device Say Device wants to write to memory. If we have the DeviceState we needn't concern whether this is a BusOneDevice or BusTwoDevice from device code itself. We would just call memory_rw(dev_state, addr, buf, size, is_write); which simply recurses through DeviceState's and BusState's through their parent pointers. The actual bus can set up those to provide identification information and perhaps hooks for translation and access checking. So memory_rw() looks like this (pseudocode): static void memory_rw(DeviceState *dev, target_phys_addr_t addr, uint8_t *buf, int size, int is_write) { BusState *bus = get_parent_bus_of_dev(dev); DeviceState *pdev = get_parent_dev(dev); target_phys_addr_t taddr; if (!bus) { /* This shouldn't happen. */ assert(0); } if (bus->responsible_for(addr)) { raw_physical_memory_rw(addr, buf, size, is_write); return; } taddr = bus->translate(dev, addr); memory_rw(pdev, taddr, buf, size, is_write); } If we do this, it seems there's no need to provide separate functions. The actual buses must instead initialize those hooks properly. Translation here is something inherent to the bus, that handles arbitration between possibly multiple IOMMUs. Our memory would normally reside on / belong to the top-level bus. What do you think? (Naming could be better though.) Eduard -- 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