On Thu, 5 Mar 2009 20:42:32 +1100
Simon Horman <horms@xxxxxxxxxxxx> wrote:
> On Thu, Mar 05, 2009 at 09:22:28AM +0000, Keir Fraser wrote:
> > On 05/03/2009 09:05, "Simon Horman" <horms@xxxxxxxxxxxx> wrote:
> >
> > > * pass-through devices may not share a GSI with another pass-through
> > > device, and its better if they don't share a GSI with an ioemu
> > > device either
> >
> > Why is such sharing disallowed? Is this a problem with mapping multiple MSI
> > sources to a single level-triggered GSI? If we can reliably map one MSI to
> > an emulated GSI, I would have thought that wire-ORing them would be easy,
> > but perhaps the emulation is dodgy to begin with, even without sharing?
>
> Shimada-san mentioned it in a previous post, hopefully he can explain further.
Please read hvm_dpci_eoi in xen/drivers/passthrough/io.c.
void hvm_dpci_eoi(struct domain *d, unsigned int guest_gsi,
union vioapic_redir_entry *ent)
{
....
device = hvm_irq_dpci->girq[guest_gsi].device;
intx = hvm_irq_dpci->girq[guest_gsi].intx;
hvm_pci_intx_deassert(d, device, intx);
machine_gsi = hvm_irq_dpci->girq[guest_gsi].machine_gsi;
Current hypervisor assumes only one pass-throughed device is connected
to a guest gsi.
It is possible to enhance to connect more than one pass-throughed
device to a guest gsi, I think. If expanding guest GSI to 143 is not
acceptable, sharing guest GSI between pass-throughed devices is one
approach.
In my understanding, Windows 2003 does not support MSI/MSI-X. So
supporting INTx is still important, I think.
Thanks,
--
Yuji Shimada
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