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

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Message-ID: <67d9e2c753a44_422c1294f@iweiny-mobl.notmuch>
Date: Tue, 18 Mar 2025 16:16:55 -0500
From: Ira Weiny <ira.weiny@...el.com>
To: "Fabio M. De Francesco" <fabio.m.de.francesco@...ux.intel.com>, "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>
CC: Robert Richter <rrichter@....com>, <ming.li@...omail.com>,
	<linux-kernel@...r.kernel.org>, <linux-cxl@...r.kernel.org>, "Fabio M. De
 Francesco" <fabio.m.de.francesco@...ux.intel.com>
Subject: Re: [PATCH 4/4 v3] cxl/test: Simulate an x86 Low Memory Hole for
 tests

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>

Reviewed-by: Ira Weiny <ira.weiny@...el.com>

[snip]