Re: Building GVT-g as a sub-module of i915

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On ma, 2016-05-23 at 07:03 +0000, Wang, Zhi A wrote:
> Hi Guys:
>   I'm trying to make GVT-g as a sub-module of i915 in the next
> version patchset. The basic idea is to introduce a "gvt-g pre-enabled 
> state" in i915. I think it should be a kernel option.
> 

Could not the GGTT partitioning be done ad hoc by moving objects out of
the memory areas to be ballooned? This way gvt module could just be
loaded and it would work, instead of having to reboot and change kernel
parameters.

> When this kernel option is enabled by user, i915 will do GGTT
> partition and save HW initial MMIO snapshot for gvt-g module during
> loading.

Like discussed in the F2F, I really think taking a MMIO snapshot in
Dom0 at boot sounds a little suspicious to me as changing Dom0 BIOS
settings could very obscurely break VM booting, especially if migration
is at some point wanted. It will also leak the Dom0 boot state to a VM,
which I do not like either.

I would be more comfortable if the VMs are booting to a driver-fixed
MMIO state.

Any thoughts by others on these?

Regards, Joonas

> When GVT-g modules is loaded, first it should check if the "gvt-g
> pre-eanbled state" is enabled in i915. If yes, then it will use the
> snapshot in i915 and continue to load. If no, then bail out.
> 
> Thanks,
> Zhi.-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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