On 10 Apr 2019, at 06:22, Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx> wrote:
On 4/6/19 2:02 AM, James Sewart wrote:
My bad, did some debugging on my end. The issue was swapping out
find_domain for iommu_get_domain_for_dev. It seems in some situations the
domain is not attached to the group but the device is expected to have the
domain still stored in its archdata.
Iâve attached the final patch with find_domain unremoved which seems to
work in my testing.
Just looked into your v3 patch set and some thoughts from my end posted
here just for your information.
Let me post the problems we want to address.
1. When allocating a new group for a device, how should we determine the
type of the default domain?
2. If we need to put a device into an existing group which uses a
different type of domain from what the device desires to use, we might
break the functionality of the device.
My new thought is letting the iommu generic code to determine the
default domain type (hence my proposed vendor specific default domain
type patches could be dropped).
If the default domain type is dynamical mapping, and later in iommu_no_mapping(), we determines that we must use an identity domain,
we then call iommu_request_dm_for_dev(dev).
If the default domain type is identity mapping, and later in
iommu_no_mapping(), we determined that we must use a dynamical domain,
we then call iommu_request_dma_domain_for_dev(dev).
We already have iommu_request_dm_for_dev() in iommu.c. We only need to
With this done, your patch titled "Create an IOMMU group for devices
that require an identity map" could also be dropped.
Theres a couple issues I can think of. iommu_request_dm_for_dev changes
the domain for all devices within the devices group, if we may have
devices with different domain requirements in the same group then only the
last initialised device will get the domain it wants. If we want to add
iommu_request_dma_domain_for_dev then we would still need another IOMMU
group for identity domain devices.
Both with v3 and the proposed method here, iommu_should_identity_map is
determining whether the device requires an identity map. In v3 this is
called once up front by the generic code to determine for the IOMMU group
which domain type to use. In the proposed method I think this would happen
after initial domain allocation and would trigger the domain to be
replaced with a different domain.
I prefer the solution in v3. What do you think?