[Xen-devel] [PATCH 0/3] [RFC] User-space grant table device

[Derek Murray <Derek.Murray@xxxxxxxxxxxx>]

I've completed a version of a Linux kernel driver for mapping granted  
pages into user-space. There are a few use cases for this, but the  
most important (from a XenSE/dom0 disaggregation point of view) is  
changing the way the the console daemon and xenstore map their  
respective pages in the guests. A further possibility might be  
reimplementing blktap entirely in user-space.
Currently the driver supports:
* Mapping one or more pages at a time into a contiguous portion of  
memory..
* Mapping up to 128 pages per file descriptor (this is an arbitrary  
limit, but it would be trivial to make this configurable).
* Each page may only be mapped once. However, it is possible to map  
the same grant more than once: simply register the grant twice with  
the ioctl, and then map the two (different) offsets.
In addition, I've written some simple libxc functions (of the same  
format as the xc_evtchn_* functions) that provide access to the driver.
I've split up the patch as follows:

1. gntdev.patch: This is the main driver, and associated header file.
2. libxc-changes.patch: These are the libxc functions for accessing  
the driver.
3. linux-changes.patch: These contain the necessary changes to linux  
(in effect, adding a hook to the vm_operations_struct that is called  
by the unmap_page_range function) for unmapping grants before the  
page table is destroyed.
I'd welcome your comments.

Regards,

Derek Murray.


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