Michael S. Tsirkin wrote:
On Mon, Apr 27, 2009 at 02:33:34PM -0400, Gregory Haskins wrote:
This allows an eventfd to be registered as an irq source with a guest. Any
signaling operation on the eventfd (via userspace or kernel) will inject
the registered GSI at the next available window.
Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
If we ever want to use this with e.g. MSI-X emulation in guest, and want
to be stricly compliant to MSI-X, we'll need a way for guest to mask
interrupts, and for host to report that a masked interrupt is pending.
Ideally, all this will be doable with a couple of mmapped pages to avoid
vmexits/system calls.
We could do this in two ways:
- move msix entry emulation into the kernel
- require the device to support replacing its irqfd, and juggle it like so:
- guest disables msi
- replace device model fd with eventfd belonging to us
- when the device fires its eventfd, set the irq pending bit
- guest enables msi
- if the pending bit is set, fire the interrupt?
- replace device model fd with the real irqfd
I'm leaning towards the latter, though it's not an easy call.
+static void
+irqfd_inject(struct work_struct *work)
+{
+ struct _irqfd *irqfd = container_of(work, struct _irqfd, work);
+ struct kvm *kvm = irqfd->kvm;
+
+ mutex_lock(&kvm->lock);
+ kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 1);
+ kvm_set_irq(kvm, KVM_USERSPACE_IRQ_SOURCE_ID, irqfd->gsi, 0);
+ mutex_unlock(&kvm->lock);
This will do weird stuff (deliver the irq twice) if the irq is
MSI/MSI-X. I know this was discussed already and is a temporary
shortcut, but maybe add a comment that we really want kvm_toggle_irq,
so that we won't forget?
If so, that's a bug. MSI should ignore kvm_set_irq(..., 0).
--
error compiling committee.c: too many arguments to function
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