On Thu, May 21, 2009 at 02:31:26PM +0100, Paul Brook wrote:> On Thursday 21 May 2009, Paul Brook wrote:> > > > MSI provides multiple edge triggered interrupts, whereas traditional> > > > mode provides a single level triggered interrupt. My guess is most> > > > devices will want to treat these differently anyway.> > >> > > So, is qemu_send_msi better than qemu_set_irq.> >> > Neither. pci_send_msi, which is a trivial wrapper around stl_phys.> > To clarify, you seem to be trying to fuse two largely separate features > together.> > MSI is a standard PCI device capability[1] that involves the device performing > a 32-bit memory write when something interesting occurs. These writes may or > may not be directed at a APIC.> > The x86 APIC has a memory mapped interface that allows generation of CPU > interrupts in response response to memory writes. These may or may not come > from an MSI capable PCI device.> > Paul> > [1] Note a *device* capability, not a bus capability. Paul, so I went over specs, and what you say about APIC here does notseem to be what Intel actually implemented. Specifically, Intelimplemented *MSI support in APIC*. This lets PCI devices, but not the CPU,signal interrupts by memory writes. For example, after reset, when CPU writes to address 0xfee00000 thisis an access to a reserved register in APIC, but when PCI devicedoes write to 0xfee00000, this triggers an interrupt to destination 0. See section 9.12 in Intel® 64 and IA-32 Architectures SoftwareDeveloper’s Manual Volume 3A: System Programming Guide, Part 1http://www.intel.com/Assets/PDF/manual/253668.pdf So it seems that what we need to do in pci is: if (!msi_ops || msi_ops->send_msi(address, data)) stl_phy(address, data); where send_msi is wired to apic_send_msi andwhere apic_send_msi returns an error for an addressoutside of the MSI range 0xfee00000 - 0xfeefffff Makes sense? -- MST_______________________________________________Virtualization mailing listVirtualization@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx://lists.linux-foundation.org/mailman/listinfo/virtualization
