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Yao Xingtao 843836bfc1 cxl/region: check interleave capability 
[ Upstream commit 84328c5ace ]

Since interleave capability is not verified, if the interleave
capability of a target does not match the region need, committing decoder
should have failed at the device end.

In order to checkout this error as quickly as possible, driver needs
to check the interleave capability of target during attaching it to
region.

Per CXL specification r3.1(8.2.4.20.1 CXL HDM Decoder Capability Register),
bits 11 and 12 indicate the capability to establish interleaving in 3, 6,
12 and 16 ways. If these bits are not set, the target cannot be attached to
a region utilizing such interleave ways.

Additionally, bits 8 and 9 represent the capability of the bits used for
interleaving in the address, Linux tracks this in the cxl_port
interleave_mask.

Per CXL specification r3.1(8.2.4.20.13 Decoder Protection):
  eIW means encoded Interleave Ways.
  eIG means encoded Interleave Granularity.

  in HPA:
  if eIW is 0 or 8 (interleave ways: 1, 3), all the bits of HPA are used,
  the interleave bits are none, the following check is ignored.

  if eIW is less than 8 (interleave ways: 2, 4, 8, 16), the interleave bits
  start at bit position eIG + 8 and end at eIG + eIW + 8 - 1.

  if eIW is greater than 8 (interleave ways: 6, 12), the interleave bits
  start at bit position eIG + 8 and end at eIG + eIW - 1.

  if the interleave mask is insufficient to cover the required interleave
  bits, the target cannot be attached to the region.

Fixes: 384e624bb2 ("cxl/region: Attach endpoint decoders")
Signed-off-by: Yao Xingtao <yaoxt.fnst@fujitsu.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Link: https://patch.msgid.link/20240614084755.59503-2-yaoxt.fnst@fujitsu.com
Signed-off-by: Dave Jiang <dave.jiang@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
History 2024-07-05 09:34:07 +02:00
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README 

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.