Ben-Ami Yassour wrote:
On Thu, 2008-07-17 at 11:31 +0300, Avi Kivity wrote:
Ben-Ami Yassour wrote:
+
+/* FIXME: Implement the OR logic needed to make shared interrupts
on + * this line behave properly + */
Isn't this a showstopper? There is no easy way for a user to avoid
sharing, especially as we have only three pci irqs at present.
What do you mean by only 3 (for passthrough we use whatever interrupt
the host is using for that device)?
There are two issue:
- shared host interrupts
- shared guest interrupts
For shared host interrupts, I don't think there's a cost-effective
solution, especially as hosts are transitioning to MSI. But the problem
the comment describes is shared guest interrupts, where the assigned
device's interrupt is shared with another device (assigned or virtual).
And currently we only have three shareable interrupts: 5, 10, and 11.
See qemu's pci_set_irq() for the logic used to share interrupts.
I think we'll leave this issue until we fix the more basic comments. In
any case, how can we make qemu configure the assigned device to share an
interrupt with another device (assigned or virtual)?
It's the guest's responsibility to assign irq lines, when running in
acpi mode. In no-acpi mode, the bios assigns lines according to an
algorithm in bios/rombios32.c:pci_bios_init_device().
--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.
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