On Sat, 2012-12-15 at 01:46 +0100, Alexander Graf wrote:
On 05.11.2012, at 04:18, Paul Mackerras wrote:
This series implements in-kernel emulation of the XICS interrupt
controller specified in the PAPR specification and used by pseries
guests. Since the XICS is organized a bit differently to the
interrupt controllers used on x86 machines, I have defined some new
ioctls for setting up the XICS and for saving and restoring its
state. It may be possible to use some of the currently x86-specific
ioctls instead.
Is this one already following the new world order that we discussed during
KVM Forum? :)
The new world order (sorry, looks like nobody took notes and
people expect me to do a write up from memory now ... :-)
Well, mostly we agreed that the x86 stuff wasn't going to work for us.
So basically what we discussed boils down to:
- Move the existing generic KVM ioctl to create the kernel APIC to
x86 since it's no as-is useful for other archs who, among other things,
might need to pass argument based on the machine type (type of interrupt
subsystem for example, etc...)
- Once that's done, well, instanciating interrupt controller objects
becomes pretty much an arch specific matter. We could try to keep some
ioctls somewhat common though it's not *that* useful because the various
types arguments are going to be fairly arch specific, so goes for
configuration. Examples of what could be kept common are:
* Create irq chip, takes at least a type argument, possibly a few
more type-specific args (or a union, but then let's keep space in there
since we can't change the size of the struct later as it would impact
the ioctl number afaik).
* Assigning the address of an irq chip when it can change (see ARM
patches)
- The existing business with irqfd etc... is mostly ok, except the
interfaces messing around with MSIs (see virtio-pci use of kvm functions
directly). The assignment of an irq number for an MSI must be a hook,
probably a PCI controller hook, so x86 can get it done via its existing
kernel interfaces and sane architectures can keep the assignment in qemu
where it belongs.
Cheers,
Ben.
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