linux-kernel - Re: [PATCH 3/3] cxl/test: Simulate an x86 Low Memory Hole for tests

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Message-ID: <Z0TiEq2xExrejxTD@aschofie-mobl2.lan>
Date: Mon, 25 Nov 2024 12:46:10 -0800
From: Alison Schofield <alison.schofield@...el.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>,
	Vishal Verma <vishal.l.verma@...el.com>,
	Ira Weiny <ira.weiny@...el.com>,
	Dan Williams <dan.j.williams@...el.com>,
	Huang Ying <ying.huang@...el.com>,
	Yao Xingtao <yaoxt.fnst@...itsu.com>, Li Ming <ming4.li@...el.com>,
	linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Subject: Re: [PATCH 3/3] cxl/test: Simulate an x86 Low Memory Hole for tests

On Fri, Nov 22, 2024 at 04:51:54PM +0100, Fabio M. De Francesco wrote:
> Simulate an x86 Low Memory Hole for the CXL tests by changing
> mock_cfmws[0] range size to 768MB and CXL Endpoint Decoder HPA range size
> to 1GB and have get_cfmws_range_start() return two different addresses
> which depend on whether the passed device is real or mock.

How about adding:

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 succesfully 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       | 21 +++++++++++++--------
>  drivers/cxl/cxl.h            |  7 +++++++
>  tools/testing/cxl/Kbuild     |  1 +
>  tools/testing/cxl/test/cxl.c |  4 ++--
>  4 files changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/cxl/core/lmh.c b/drivers/cxl/core/lmh.c
> index da76b2a534ec..350008324bdc 100644
> --- a/drivers/cxl/core/lmh.c
> +++ b/drivers/cxl/core/lmh.c
> @@ -1,10 +1,15 @@
>  // SPDX-License-Identifier: GPL-2.0-only
>  
>  #include <linux/range.h>
> +#include <linux/pci.h>
>  #include "cxl.h"
>  
> -/* In x86 with memory hole, misaligned CFMWS range starts at 0x0 */
> -#define MISALIGNED_CFMWS_RANGE_BASE 0x0
> +u64 get_cfmws_range_start(struct device *dev)

Can this func be static, and then keep the #defines here, in lmh.c,
rather than move to cxl.h ?


> +{
> +	if (dev_is_pci(dev))
> +		return MISALIGNED_CFMWS_RANGE_START;

space before final return please

> +	return MISALIGNED_MOCK_CFMWS_RANGE_START;
> +}
>  

snip


> diff --git a/drivers/cxl/cxl.h b/drivers/cxl/cxl.h
> index a5ad4499381e..51dc80f8e50c 100644
> --- a/drivers/cxl/cxl.h
> +++ b/drivers/cxl/cxl.h
> @@ -903,12 +903,19 @@ void cxl_coordinates_combine(struct access_coordinate *out,
>  bool cxl_endpoint_decoder_reset_detected(struct cxl_port *port);
>  
>  #ifdef CONFIG_CXL_ARCH_LOW_MEMORY_HOLE
> +
> +/* Range start address of misaligned CFMWS in x86 with LMH */
> +#define MISALIGNED_CFMWS_RANGE_START 0x0
> +/* Range start address of mock misaligned CFMWS for tests */
> +#define MISALIGNED_MOCK_CFMWS_RANGE_START 0xf010000000
> +

As noted above, wondering why these need to be in cxl.h

Why 'MISALIGNED_ and not 'LMH_' , especially if you can move to lmh.c.

Is it guaranteed that MOCK_CFMWS_RANGE_START is at 0xf010000000?

-- Alison


snip to end