linux-kernel - Re: [PATCH 4/4 v3] cxl/test: Simulate an x86 Low Memory Hole for tests

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Message-ID: <Z91CgQjzXzKWNXPX@rric.localdomain>
Date: Fri, 21 Mar 2025 11:42:09 +0100
From: Robert Richter <rrichter@....com>
To: "Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>
Cc: Davidlohr Bueso <dave@...olabs.net>,
	Jonathan Cameron <jonathan.cameron@...wei.com>,
	Dave Jiang <dave.jiang@...el.com>,
	Alison Schofield <alison.schofield@...el.com>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Dan Williams <dan.j.williams@...el.com>, ming.li@...omail.com,
	linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Subject: Re: [PATCH 4/4 v3] cxl/test: Simulate an x86 Low Memory Hole for
 tests

On 14.03.25 12:36:33, Fabio M. De Francesco wrote:
> Simulate an x86 Low Memory Hole for the CXL tests by changing the first
> mock CFMWS range size to 768MB and the CXL Endpoint Decoder HPA range sizes
> to 1GB.
> 
> Since the auto-created region of cxl-test uses mock_cfmws[0], whose range
> base address is typically different from the one published by the BIOS on
> real hardware, the driver would fail to create and attach CXL Regions if
> it was run on the mock environment created by cxl-tests.
> 
> Therefore, save the mock_cfmsw[0] range base_hpa and reuse it to match CXL
> Root Decoders and Regions with Endpoint Decoders when the driver is run on
> mock devices.
> 
> Since the auto-created region of cxl-test uses mock_cfmws[0], the
> LMH path in the CXL Driver will be exercised every time the cxl-test
> module is loaded. Executing unit test: cxl-topology.sh, confirms the
> region created successfully with a LMH.
> 
> Cc: Alison Schofield <alison.schofield@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Ira Weiny <ira.weiny@...el.com>
> Signed-off-by: Fabio M. De Francesco <fabio.m.de.francesco@...ux.intel.com>
> ---
>  drivers/cxl/core/lmh.c               | 35 ++++++++++++++++++++++++----
>  drivers/cxl/core/lmh.h               |  2 ++

Can you take a look to move all those changes to testing/? This
indicates the interface of your mock functions need improvement.

-Robert

>  tools/testing/cxl/cxl_core_exports.c |  2 ++
>  tools/testing/cxl/test/cxl.c         | 10 ++++++++
>  4 files changed, 45 insertions(+), 4 deletions(-)