[PATCH] cxl/test: Update mock memdev array before calling platform_device_add()

[PATCH] cxl/test: Update mock memdev array before calling platform_device_add()

[Li Ming]

CXL test environment hits the following error sometimes.

 cxl_mem mem9: endpoint7 failed probe

All mock memdevs are platform firmware devices added by cxl_test module,
and cxl_test module also provides a platform device driver for them to
create a memdev device to CXL subsystem. cxl_test module uses
cxl_rcd/mem_single/mem arrays to store different types of mock memdevs.
CXL drivers calls registered mock functions for a mock memdev by
checking if a given memdev is in these arrays.

When cxl_test module adds these mock memdevs, it always calls
platform_device_add() before adding them to a suitable mock memdev
array. However, there is a small window where CXL drivers calls mock
function for a added memdev before it added to a mock memdev array. In
above case, cxl endpoint driver considers a added memdev was not a mock
memdev, then calling devm_cxl_endpoint_decoders_setup() for it rather
than mock_endpoint_decoders_setup().

An appropriate solution is that adding a new mock memdev to a mock
memdev array before calling platform_device_add() for it. It can
guarantee the new mock memdev is visible to CXL subsystem.

Fixes: 3a2b97b3210b ("cxl/test: Improve init-order fidelity relative to real-world systems")
Signed-off-by: Li Ming <ming.li@zohomail.com>
---
 tools/testing/cxl/test/cxl.c | 9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
index 81e2aef3627a..2664c9de8dd6 100644
--- a/tools/testing/cxl/test/cxl.c
+++ b/tools/testing/cxl/test/cxl.c
@@ -1356,12 +1356,13 @@ static int cxl_mem_init(void)
 		pdev->dev.parent = &dport->dev;
 		set_dev_node(&pdev->dev, i % 2);
 
+		cxl_mem[i] = pdev;
 		rc = platform_device_add(pdev);
 		if (rc) {
 			platform_device_put(pdev);
+			cxl_mem[i] = NULL;
 			goto err_mem;
 		}
-		cxl_mem[i] = pdev;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(cxl_mem_single); i++) {
@@ -1374,12 +1375,13 @@ static int cxl_mem_init(void)
 		pdev->dev.parent = &dport->dev;
 		set_dev_node(&pdev->dev, i % 2);
 
+		cxl_mem_single[i] = pdev;
 		rc = platform_device_add(pdev);
 		if (rc) {
 			platform_device_put(pdev);
+			cxl_mem_single[i] = NULL;
 			goto err_single;
 		}
-		cxl_mem_single[i] = pdev;
 	}
 
 	for (i = 0; i < ARRAY_SIZE(cxl_rcd); i++) {
@@ -1393,12 +1395,13 @@ static int cxl_mem_init(void)
 		pdev->dev.parent = &rch->dev;
 		set_dev_node(&pdev->dev, i % 2);
 
+		cxl_rcd[i] = pdev;
 		rc = platform_device_add(pdev);
 		if (rc) {
 			platform_device_put(pdev);
+			cxl_rcd[i] = NULL;
 			goto err_rcd;
 		}
-		cxl_rcd[i] = pdev;
 	}
 
 	return 0;

---
base-commit: 19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4
change-id: 20260306-update_array_before_adding_mock_memdev-89673b4d9118

Best regards,
-- 
Li Ming <ming.li@zohomail.com>

Re: [PATCH] cxl/test: Update mock memdev array before calling platform_device_add()

[Dave Jiang]

On 3/6/26 7:28 AM, Li Ming wrote:
> CXL test environment hits the following error sometimes.
> 
>  cxl_mem mem9: endpoint7 failed probe
> 
> All mock memdevs are platform firmware devices added by cxl_test module,
> and cxl_test module also provides a platform device driver for them to
> create a memdev device to CXL subsystem. cxl_test module uses
> cxl_rcd/mem_single/mem arrays to store different types of mock memdevs.
> CXL drivers calls registered mock functions for a mock memdev by
> checking if a given memdev is in these arrays.
> 
> When cxl_test module adds these mock memdevs, it always calls
> platform_device_add() before adding them to a suitable mock memdev
> array. However, there is a small window where CXL drivers calls mock
> function for a added memdev before it added to a mock memdev array. In
> above case, cxl endpoint driver considers a added memdev was not a mock
> memdev, then calling devm_cxl_endpoint_decoders_setup() for it rather
> than mock_endpoint_decoders_setup().
> 
> An appropriate solution is that adding a new mock memdev to a mock
> memdev array before calling platform_device_add() for it. It can
> guarantee the new mock memdev is visible to CXL subsystem.
> 
> Fixes: 3a2b97b3210b ("cxl/test: Improve init-order fidelity relative to real-world systems")
> Signed-off-by: Li Ming <ming.li@zohomail.com>

Makes sense.
Reviewed-by: Dave Jiang <dave.jiang@intel.com>


> ---
>  tools/testing/cxl/test/cxl.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> index 81e2aef3627a..2664c9de8dd6 100644
> --- a/tools/testing/cxl/test/cxl.c
> +++ b/tools/testing/cxl/test/cxl.c
> @@ -1356,12 +1356,13 @@ static int cxl_mem_init(void)
>  		pdev->dev.parent = &dport->dev;
>  		set_dev_node(&pdev->dev, i % 2);
>  
> +		cxl_mem[i] = pdev;
>  		rc = platform_device_add(pdev);
>  		if (rc) {
>  			platform_device_put(pdev);
> +			cxl_mem[i] = NULL;
>  			goto err_mem;
>  		}
> -		cxl_mem[i] = pdev;
>  	}
>  
>  	for (i = 0; i < ARRAY_SIZE(cxl_mem_single); i++) {
> @@ -1374,12 +1375,13 @@ static int cxl_mem_init(void)
>  		pdev->dev.parent = &dport->dev;
>  		set_dev_node(&pdev->dev, i % 2);
>  
> +		cxl_mem_single[i] = pdev;
>  		rc = platform_device_add(pdev);
>  		if (rc) {
>  			platform_device_put(pdev);
> +			cxl_mem_single[i] = NULL;
>  			goto err_single;
>  		}
> -		cxl_mem_single[i] = pdev;
>  	}
>  
>  	for (i = 0; i < ARRAY_SIZE(cxl_rcd); i++) {
> @@ -1393,12 +1395,13 @@ static int cxl_mem_init(void)
>  		pdev->dev.parent = &rch->dev;
>  		set_dev_node(&pdev->dev, i % 2);
>  
> +		cxl_rcd[i] = pdev;
>  		rc = platform_device_add(pdev);
>  		if (rc) {
>  			platform_device_put(pdev);
> +			cxl_rcd[i] = NULL;
>  			goto err_rcd;
>  		}
> -		cxl_rcd[i] = pdev;
>  	}
>  
>  	return 0;
> 
> ---
> base-commit: 19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4
> change-id: 20260306-update_array_before_adding_mock_memdev-89673b4d9118
> 
> Best regards,

Re: [PATCH] cxl/test: Update mock memdev array before calling platform_device_add()

[Alison Schofield]

On Fri, Mar 06, 2026 at 10:28:19PM +0800, Li Ming wrote:
> CXL test environment hits the following error sometimes.
> 
>  cxl_mem mem9: endpoint7 failed probe
> 
> All mock memdevs are platform firmware devices added by cxl_test module,
> and cxl_test module also provides a platform device driver for them to
> create a memdev device to CXL subsystem. cxl_test module uses
> cxl_rcd/mem_single/mem arrays to store different types of mock memdevs.
> CXL drivers calls registered mock functions for a mock memdev by
> checking if a given memdev is in these arrays.
> 
> When cxl_test module adds these mock memdevs, it always calls
> platform_device_add() before adding them to a suitable mock memdev
> array. However, there is a small window where CXL drivers calls mock
> function for a added memdev before it added to a mock memdev array. In
> above case, cxl endpoint driver considers a added memdev was not a mock
> memdev, then calling devm_cxl_endpoint_decoders_setup() for it rather
> than mock_endpoint_decoders_setup().
> 
> An appropriate solution is that adding a new mock memdev to a mock
> memdev array before calling platform_device_add() for it. It can
> guarantee the new mock memdev is visible to CXL subsystem.

Hi Ming,

Thanks, I was able to reproduce this as well while testing a new
configuration with 12 memdevs, and your fix resolved it, so...

Reviewed-by: Alison Schofield <alison.schofield@intel.com>
Tested-by: Alison Schofield <alison.schofield@intel.com>

However, since this is a low frequency nuisance now, and given
that it now touches all three mock memdev arrays, and I am
heading towards adding a fourth (which is how I hit this), it would
be nice to tidy this code up before fixing. Refactor the repeated
platform_device_alloc()/platform_device_add() pattern into a helper.
That would let the ordering rule live in one place rather than 3 or 4.

-- Alison


> 
> Fixes: 3a2b97b3210b ("cxl/test: Improve init-order fidelity relative to real-world systems")
> Signed-off-by: Li Ming <ming.li@zohomail.com>
> ---
>  tools/testing/cxl/test/cxl.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/tools/testing/cxl/test/cxl.c b/tools/testing/cxl/test/cxl.c
> index 81e2aef3627a..2664c9de8dd6 100644
> --- a/tools/testing/cxl/test/cxl.c
> +++ b/tools/testing/cxl/test/cxl.c
> @@ -1356,12 +1356,13 @@ static int cxl_mem_init(void)
>  		pdev->dev.parent = &dport->dev;
>  		set_dev_node(&pdev->dev, i % 2);
>  
> +		cxl_mem[i] = pdev;
>  		rc = platform_device_add(pdev);
>  		if (rc) {
>  			platform_device_put(pdev);
> +			cxl_mem[i] = NULL;
>  			goto err_mem;
>  		}
> -		cxl_mem[i] = pdev;
>  	}
>  
>  	for (i = 0; i < ARRAY_SIZE(cxl_mem_single); i++) {
> @@ -1374,12 +1375,13 @@ static int cxl_mem_init(void)
>  		pdev->dev.parent = &dport->dev;
>  		set_dev_node(&pdev->dev, i % 2);
>  
> +		cxl_mem_single[i] = pdev;
>  		rc = platform_device_add(pdev);
>  		if (rc) {
>  			platform_device_put(pdev);
> +			cxl_mem_single[i] = NULL;
>  			goto err_single;
>  		}
> -		cxl_mem_single[i] = pdev;
>  	}
>  
>  	for (i = 0; i < ARRAY_SIZE(cxl_rcd); i++) {
> @@ -1393,12 +1395,13 @@ static int cxl_mem_init(void)
>  		pdev->dev.parent = &rch->dev;
>  		set_dev_node(&pdev->dev, i % 2);
>  
> +		cxl_rcd[i] = pdev;
>  		rc = platform_device_add(pdev);
>  		if (rc) {
>  			platform_device_put(pdev);
> +			cxl_rcd[i] = NULL;
>  			goto err_rcd;
>  		}
> -		cxl_rcd[i] = pdev;
>  	}
>  
>  	return 0;
> 
> ---
> base-commit: 19d2f0b97a131198efc2c4ca3eb7f980bba8c2b4
> change-id: 20260306-update_array_before_adding_mock_memdev-89673b4d9118
> 
> Best regards,
> -- 
> Li Ming <ming.li@zohomail.com>
>