[Xen-devel] latest USB code

[harry <harry@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx>]

Here's the latest USB code against the xen 3.0.0 release.  Since the
last posting this version updates the code to use the new 32 bit grant
references and the latest GNTTABOP_map_grant_ref definition.  I've also
changed the definition of the virtual USB HCD to have a single port
rather than seven ports with six unused.  Domains importing multiple USB
devices will get a HCD for each device (this feature currently
untested).  I went with this solution because it scales indefinitely.

This code passes the usual sniff test of mounting a filesystem on a USB
key.

The issues that I know about that remain with this code are as follows:

o - The USB protocol requires stalling the URB queue during error
conditions.  This isn't done correctly yet which makes the code unsafe
for write access during error recovery.

o - The resource pools are currently only allocating the minimum
resources required to avoid deadlock so performance will be resource
constrained.  This can be fixed either by implementing a larger static
resource allocation or improving the buffer_resource_provider to
implement a dynamic shared resource pool.  Either is fairly easy.

o - You no longer need to specify swiotlb=force because xen has a small
swiotlb turned on by default.  If you explicitly turn the swiotlb off,
the USB code will still be broken.

o - The USB-specific part of the interdomain protocol is using polling
for device discovery which is inefficient.  I looked into fixing this
and it won't be too hard to change the protocol so that the BE sends a
message to the FE to kick the FE into re-probing the BE.  This will make
the BE device state machine a bit more complicated.

o - Design documentation for the USB driver is required.

o - We might not want to keep the xenidc code.  API documentation for
the xenidc API is required if we are going to keep the xenidc code.

o - Isochronous URBs are untested.

o - My test machine is USB 1.2 and I've not yet tested with USB 2.0.

o - Suspend and resume is untested.  Domain migration is untested.

o - I've only ever tried to build the code for X86 and never X86_64.

o - Automated tests integrated with the xm-test framework would be good.

o - Need to run the USB part by the usb mailing list once I fix the
protocol and think it's OK.

I split the patch into two just in case anyone wants to play with the
xenidc code.

Attachment: latest-xenidc-patch.gz
Description: GNU Zip compressed data

Attachment: latest-usb-patch.gz
Description: GNU Zip compressed data

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