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Re: [Xen-devel] Requesting for freeze exception for ARM/ITS patches


On 10/07/2015 17:52, Ian Campbell wrote:
On Fri, 2015-07-10 at 12:01 +0100, Jan Beulich wrote:
On 10.07.15 at 12:46, <vijay.kilari@xxxxxxxxx> wrote:
     I would like to have freeze exception for ITS feature on ARM64.
Design got freeze few weeks back and I have sent v4 version of patch series

This patches will not impact any generic code of other platforms and have
changes generic arm related code. Also these patches are only for
ARM64 platform.

These patches are pre-requisite for PCI support / Pass-through support
on ARM64 platforms.

But what good will it do for the release when it's only a prereq for
further work?

I think this may have been true of v3 but I think it is underselling v4.
AFAICT with the final patch in v4 Xen will actually be capable of
booting on a ThunderX platform and starting guests. It will simply lack
PCI passthrough capabilities (as do all ARM platforms today).

I think you are overselling this patch series. PCI devices provide the support of both legacy interrupt and MSI.

The former is handled by your PCI patch series [1] pushed upstreamed few days ago. This should be enough for booting ThunderX and creating guests.

The ITS add the support of MSI which is useful for performance question and PCI passthrough.

I think that's a reasonable thing to try and get into 4.6.

If we ever decide to get this into 4.6 we need some guarantee from Cavium to finish the work afterwards.


[1] http://lists.xen.org/archives/html/xen-devel/2015-07/msg00656.html

Julien Grall

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