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To support disassociation and PCI hot unplug, we have to track all the VMAs that refer to the device IO memory. When disassociation occurs the VMAs have to be revised to point to the zero page, not the IO memory, to allow the physical HW to be unplugged. The three drivers supporting this implemented three different versions of this algorithm, all leaving something to be desired. This new common implementation has a few differences from the driver versions: - Track all VMAs, including splitting/truncating/etc. Tie the lifetime of the private data allocation to the lifetime of the vma. This avoids any tricks with setting vm_ops which Linus didn't like. (see link) - Support multiple mms, and support properly tracking mmaps triggered by processes other than the one first opening the uverbs fd. This makes fork behavior of disassociation enabled drivers the same as fork support in normal drivers. - Don't use crazy get_task stuff. - Simplify the approach for to racing between vm_ops close and disassociation, fixing the related bugs most of the driver implementations had. Since we are in core code the tracking list can be placed in struct ib_uverbs_ufile, which has a lifetime strictly longer than any VMAs created by mmap on the uverbs FD. Link: https://www.spinics.net/lists/stable/msg248747.html Link: https://lkml.kernel.org/r/CA+55aFxJTV_g46AQPoPXen-UPiqR1HGMZictt7VpC-SMFbm3Cw@mail.gmail.com Signed-off-by: Jason Gunthorpe <jgg@mellanox.com> Signed-off-by: Leon Romanovsky <leonro@mellanox.com> Signed-off-by: Doug Ledford <dledford@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.