The qpn allocation logic has a WARN_ON() that intends to detect the use of
an index that will introduce bits in the lower order bits of the QOS bits
in the QPN.
Unfortunately, it has the following bugs:
- it misfires when wrapping QPN allocation for non-QOS
- it doesn't correctly detect low order QOS bits (despite the comment)
The WARN_ON() should not be applied to non-QOS (qos_shift == 1).
Additionally, it SHOULD test the qpn bits per the table below:
2 data VLs: [qp7, qp6, qp5, qp4, qp3, qp2, qp1] ^
[ 0, 0, 0, 0, 0, 0, sc0], qp bit 1 always 0*
3-4 data VLs: [qp7, qp6, qp5, qp4, qp3, qp2, qp1] ^
[ 0, 0, 0, 0, 0, sc1, sc0], qp bits [21] always 0
5-8 data VLs: [qp7, qp6, qp5, qp4, qp3, qp2, qp1] ^
[ 0, 0, 0, 0, sc2, sc1, sc0] qp bits [321] always 0
Fix by qualifying the warning for qos_shift > 1 and producing the correct
mask to insure the above bits are zero without generating a superfluous
warning.
Fixes: 501edc4244 ("IB/rdmavt: Correct warning during QPN allocation")
Reviewed-by: Kaike Wan <kaike.wan@intel.com>
Signed-off-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Signed-off-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.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.
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.
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