Hello Sai, Baolu,
On Sun, Feb 16, 2020 at 01:57:26PM -0800, Sai Praneeth Prakhya wrote:
> Hence it will be helpful if there is some way to change the default
> domain of a B:D.F dynamically. Since, linux iommu subsystem prefers to
> deal at iommu_group level instead of B:D.F level, it might be helpful
> if there is some way to change the default domain of a *iommu_group*
> dynamically. Hence, add such support.
The question is how this plays together with the per-device private
domains in the Intel VT-d driver. I recently debugged an issue there and
I think there are more. The overall code for this seems to be pretty
fragile, so I had the idea to make the private default domains more
general.
IOMMU default domains don't necessarily need to stick to the iommu-group
granularity, because the default domain is used by in-kernel drivers
only, and the kernel trusts itself.
So my idea was to make the private-domain concept of the VT-d driver
more generic and move it to the iommu core code. With that we can
configure real per-device default domain types and don't have the race
condition with driver probing when changing the default domain of
multiple devices. We have to limit the ability to change default domain
types to devices with no PCI aliases, but that should not be a problem
for the intended use-case.
What do you think?
Regards,
Joerg
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