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

[Simon Horman <horms@xxxxxxxxxxxx>]

On Wed, Feb 18, 2009 at 12:12:27PM +0900, Yuji Shimada wrote:
> 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)

To be honest I am a little confused about what the above maping
is supposed to achive.

-- 
Simon Horman
  VA Linux Systems Japan K.K., Sydney, Australia Satellite Office
  H: www.vergenet.net/~horms/             W: www.valinux.co.jp/en


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