Re: [Xen-devel] [rfc 00/18] ioemu: use devfn instead of slots as the unit for passthrough

[Yuji Shimada <shimada-yxb@xxxxxxxxxxxxxxx>]

On Tue, 17 Feb 2009 20:07:48 +1100
Simon Horman <horms@xxxxxxxxxxxx> wrote:

> This series starts of with servaral cleanup patches.
> 
> The meat of the changes start with the patch
> "ioemu: use devfn instead of slots as the unit for passthrough"
> 
> This allows multi-function cards to be appear in guets as
> multi-function cards, with the restriction that function 0 must
> be passed through. Otherwise each function is allocated its own
> slot, as before.

How do you guarantee that virtual gsi is not shared between
pass-throughed devices? Xen hypervisor does not support sharing
virtual gsi between pass-throughed devices.

The function 0 always uses INTA. The function 1-7 might use INTB-INTD.
INTB-INTD will route to the same virtual gsi with other device's
INTA-INTD.

Current interrupt routing in xen hypervisor is defined as follows.

xen/include/asm-x86/hvm/irq.h
#define hvm_pci_intx_gsi(dev, intx)  \
    (((((dev)<<2) + ((dev)>>3) + (intx)) & 31) + 16)

Thanks,
--
Yuji Shimada


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