[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [Xen-devel] RFC: [PATCH 1/3] Enhance platform support for PCI

On 24/02/15 7:13 pm, Julien Grall wrote:
On 24/02/15 00:23, Manish Jaggi wrote:
Because you have to parse all the device tree to remove the reference
to the second ITS. It's pointless and can be difficult to do it.

Could you please describe the case where it is difficult
You have to parse every node in the device tree and replace the
msi-parent properties with only one ITS.
Thats the idea.

If you are able to emulate on ITS, you can do it for multiple one.
keeping it simple and similar across dom0/domUs
Consider a case where a domU is assigned two PCI devices which are
attached to different nodes. (Node is an entity having its own cores are
host controllers).
The DOM0 view and guest view of the hardware are different.

In the case of DOM0, we want to expose the same hardware layout as the
host. So if there is 2 ITS then we should expose the 2 ITS.
AFAIK Xen has a microkernel design and timer/mmu/smmu/gic/its are handled by xen and a virtualized interface is provided to the guest. So if none of SMMU in the layout of host is presented to dom0 the same can be valid for multiple ITS.

In the case of the Guest, we (Xen) controls the memory layout.
For Dom0 as well.
we can expose only one ITS.
If we follow 2 ITS in dom0 and 1 ITS in domU, how do u expect the Xen GIC ITS emulation driver to work. It should check that request came from a dom0 handle it differently. I think this would be *difficult*.

IHMO, any ITS trap before this is wrong.
AFAIK guest always sees a virtual ITS, could you please explain what is
wrong in trapping.
I never say the trapping is wrong in all case.... The "before" was
here for any trap before the PCI has been added to Xen is, IHMO, wrong.

There is no trap before.
So I still don't understand why you need to parse the device tree node
for PCI device at boot time...

If it doesn't trap before, you should not need to know the PCI.


Xen-devel mailing list



Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.