Alexey Kardashevskiy <a...@ozlabs.ru> writes: > On 06/21/2013 08:31 PM, Alexander Graf wrote: >> >> 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? > > > I do not understand the question, really. Here we are emulating pHyp which > is not real hardware and never pretended to be. Our guests do not touch MSI > records in the config space and use RTAS MSI calls instead.
But RTAS is implemented as guest code. I suspect it's doing region access to generate the actual MSI events. Regards, Anthony Liguori > > >> >> >> 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> >> > > > -- > Alexey
