On 21.06.2013, at 11:22, Alexey Kardashevskiy wrote: > Previously every PCI host bridge implemented its own MSI memory window > in order to catch msi_notify()/msix_notify() calls from various QEMU > MSI-capable devives such as virtio-pci or vfio and redirect them to > the guest via qemu_pulse_irq().
That's how hardware works, no? > > The encoded MSIMessage used to be encoded as: > * .addr - address in a MSI window, this is how QEMU knows which PHB > is the message for; > * .data - number of a device on a specific PHB and vector number. > > As a PHB has a destriptor for every device, and every descriptor has > first IRQ number and the number of IRQs, it can calculate global IRQ > number to use in qemu_pulse_irq(). How does this work on real hardware? Alex > However the total number of IRQs is not really big (at the moment it is > 1024 IRQs which start from 4096) and the existing system looks overdesigned. > The patch simplifies it. Specifically: > > 1. MSI windows were removed from PHB. > 2. Added one memory region for all MSIs. > 3. Now MSIMessage::addr is a number of first IRQ of a device, > MSIMessage:data is a number of a vector. > > Putting IRQ number to .data and not using .addr would make it even simpler > for MSI-X but it will not work for MSI with multiple vectors unless a first > IRQ number of a device is aligned to the MSI vectors number. > > The simplified scheme also allows easier MSIMessage->IRQ translation > for upcoming IRQFD support. > > Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru>
