[v2,08/15] cxl: indicate probe deferral

Message ID	20240715172835.24757-9-alejandro.lucero-palau@amd.com (mailing list archive)
State	Not Applicable
Delegated to:	Netdev Maintainers
Headers	show Received: from NAM02-SN1-obe.outbound.protection.outlook.com (mail-sn1nam02on2089.outbound.protection.outlook.com [40.107.96.89]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 035F76CDC0; Mon, 15 Jul 2024 17:28:59 +0000 (UTC) Received-SPF: Pass (protection.outlook.com: domain of amd.com designates 165.204.84.17 as permitted sender) receiver=protection.outlook.com; client-ip=165.204.84.17; helo=SATLEXMB04.amd.com; pr=C From: <alejandro.lucero-palau@amd.com> To: <linux-cxl@vger.kernel.org>, <netdev@vger.kernel.org>, <dan.j.williams@intel.com>, <martin.habets@xilinx.com>, <edward.cree@amd.com>, <davem@davemloft.net>, <kuba@kernel.org>, <pabeni@redhat.com>, <edumazet@google.com>, <richard.hughes@amd.com> CC: Alejandro Lucero <alucerop@amd.com> Subject: [PATCH v2 08/15] cxl: indicate probe deferral Date: Mon, 15 Jul 2024 18:28:28 +0100 Message-ID: <20240715172835.24757-9-alejandro.lucero-palau@amd.com> In-Reply-To: <20240715172835.24757-1-alejandro.lucero-palau@amd.com> References: <20240715172835.24757-1-alejandro.lucero-palau@amd.com> Precedence: bulk MIME-Version: 1.0 Content-Type: text/plain Received-SPF: None (SATLEXMB04.amd.com: alejandro.lucero-palau@amd.com does not designate permitted sender hosts)
Series	cxl: add Type2 device support \| expand [v2,00/15] cxl: add Type2 device support [v2,01/15] cxl: add type2 device basic support [v2,02/15] cxl: add function for type2 cxl regs setup [v2,03/15] cxl: add function for type2 resource request [v2,04/15] cxl: add capabilities field to cxl_dev_state [v2,05/15] cxl: fix use of resource_contains [v2,06/15] cxl: add function for setting media ready by an accelerator [v2,07/15] cxl: support type2 memdev creation [v2,08/15] cxl: indicate probe deferral [v2,09/15] cxl: define a driver interface for HPA free space enumaration [v2,10/15] cxl: define a driver interface for DPA allocation [v2,11/15] cxl: make region type based on endpoint type [v2,12/15] cxl: allow region creation by type2 drivers [v2,13/15] cxl: preclude device memory to be used for dax [v2,14/15] cxl: add function for obtaining params from a region [v2,15/15] efx: support pio mapping based on cxl

Lucero Palau, Alejandro July 15, 2024, 5:28 p.m. UTC

From: Alejandro Lucero <alucerop@amd.com>

The first stop for a CXL accelerator driver that wants to establish new
CXL.mem regions is to register a 'struct cxl_memdev. That kicks off
cxl_mem_probe() to enumerate all 'struct cxl_port' instances in the
topology up to the root.

If the root driver has not attached yet the expectation is that the
driver waits until that link is established. The common cxl_pci_driver
has reason to keep the 'struct cxl_memdev' device attached to the bus
until the root driver attaches. An accelerator may want to instead defer
probing until CXL resources can be acquired.

Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
accelerator driver probing should be defferred vs failed. Provide that
indication via a new cxl_acquire_endpoint() API that can retrieve the
probe status of the memdev.

The first consumer of this API is a test driver that excercises the CXL
Type-2 flow.

Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2

Signed-off-by: Alejandro Lucero <alucerop@amd.com>
Co-developed-by: Dan Williams <dan.j.williams@intel.com>
---
 drivers/cxl/core/memdev.c          | 41 ++++++++++++++++++++++++++++++
 drivers/cxl/core/port.c            |  2 +-
 drivers/cxl/mem.c                  |  7 +++--
 drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
 include/linux/cxl_accel_mem.h      |  3 +++
 5 files changed, 59 insertions(+), 4 deletions(-)

Li, Ming4 July 16, 2024, 5:52 a.m. UTC | #1

On 7/16/2024 1:28 AM, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
>
> The first stop for a CXL accelerator driver that wants to establish new
> CXL.mem regions is to register a 'struct cxl_memdev. That kicks off
> cxl_mem_probe() to enumerate all 'struct cxl_port' instances in the
> topology up to the root.
>
> If the root driver has not attached yet the expectation is that the
> driver waits until that link is established. The common cxl_pci_driver
> has reason to keep the 'struct cxl_memdev' device attached to the bus
> until the root driver attaches. An accelerator may want to instead defer
> probing until CXL resources can be acquired.
>
> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
> accelerator driver probing should be defferred vs failed. Provide that
> indication via a new cxl_acquire_endpoint() API that can retrieve the
> probe status of the memdev.
>
> The first consumer of this API is a test driver that excercises the CXL
> Type-2 flow.
>
> Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
>
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/core/memdev.c          | 41 ++++++++++++++++++++++++++++++
>  drivers/cxl/core/port.c            |  2 +-
>  drivers/cxl/mem.c                  |  7 +++--
>  drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>  include/linux/cxl_accel_mem.h      |  3 +++
>  5 files changed, 59 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index b902948b121f..d51c8bfb32e3 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>  
> +/*
> + * Try to get a locked reference on a memdev's CXL port topology
> + * connection. Be careful to observe when cxl_mem_probe() has deposited
> + * a probe deferral awaiting the arrival of the CXL root driver
> +*/
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_port *endpoint;
> +	int rc = -ENXIO;
> +
> +	device_lock(&cxlmd->dev);
> +	endpoint = cxlmd->endpoint;
> +	if (!endpoint)
> +		goto err;
> +
> +	if (IS_ERR(endpoint)) {
> +		rc = PTR_ERR(endpoint);
> +		goto err;
> +	}
> +
> +	device_lock(&endpoint->dev);
> +	if (!endpoint->dev.driver)
> +		goto err_endpoint;
> +
> +	return endpoint;
> +
> +err_endpoint:
> +	device_unlock(&endpoint->dev);
> +err:
> +	device_unlock(&cxlmd->dev);
> +	return ERR_PTR(rc);
> +}
> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
> +
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint)
> +{
> +	device_unlock(&endpoint->dev);
> +	device_unlock(&cxlmd->dev);
> +}
> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
> +
>  static void sanitize_teardown_notifier(void *data)
>  {
>  	struct cxl_memdev_state *mds = data;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index d66c6349ed2d..3c6b896c5f65 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
>  		 */
>  		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>  			dev_name(dport_dev));
> -		return -ENXIO;
> +		return -EPROBE_DEFER;
>  	}
>  
>  	parent_port = find_cxl_port(dparent, &parent_dport);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index f76af75a87b7..383a6f4829d3 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>  		return rc;
>  
>  	rc = devm_cxl_enumerate_ports(cxlmd);
> -	if (rc)
> +	if (rc) {
> +		cxlmd->endpoint = ERR_PTR(rc);
>  		return rc;
> +	}
>  
>  	parent_port = cxl_mem_find_port(cxlmd, &dport);
>  	if (!parent_port) {
>  		dev_err(dev, "CXL port topology not found\n");
> -		return -ENXIO;
> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
> +		return -EPROBE_DEFER;
>  	}
>  
>  	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM)) {
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> index 0abe66490ef5..2cf4837ddfc1 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.c
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -65,8 +65,16 @@ void efx_cxl_init(struct efx_nic *efx)
>  	}
>  
>  	cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds);
> -	if (IS_ERR(cxl->cxlmd))
> +	if (IS_ERR(cxl->cxlmd)) {
>  		pci_info(pci_dev, "CXL accel memdev creation failed");
> +		return;
> +	}
> +
> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
> +	if (IS_ERR(cxl->endpoint))
> +		pci_info(pci_dev, "CXL accel acquire endpoint failed");
> +
> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);

there is no need to invoke cxl_release_endpoint() if cxl_acquire_endpoint() failed. right?


>  }
>  
>  
> diff --git a/include/linux/cxl_accel_mem.h b/include/linux/cxl_accel_mem.h
> index 442ed9862292..701910021df8 100644
> --- a/include/linux/cxl_accel_mem.h
> +++ b/include/linux/cxl_accel_mem.h
> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state *cxlds);
>  
>  struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  				       struct cxl_dev_state *cxlds);
> +
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd);
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint);
>  #endif

Alejandro Lucero Palau July 16, 2024, 8:10 a.m. UTC | #2

On 7/16/24 06:52, Li, Ming4 wrote:
> On 7/16/2024 1:28 AM, alejandro.lucero-palau@amd.com wrote:
>> From: Alejandro Lucero <alucerop@amd.com>
>>
>> The first stop for a CXL accelerator driver that wants to establish new
>> CXL.mem regions is to register a 'struct cxl_memdev. That kicks off
>> cxl_mem_probe() to enumerate all 'struct cxl_port' instances in the
>> topology up to the root.
>>
>> If the root driver has not attached yet the expectation is that the
>> driver waits until that link is established. The common cxl_pci_driver
>> has reason to keep the 'struct cxl_memdev' device attached to the bus
>> until the root driver attaches. An accelerator may want to instead defer
>> probing until CXL resources can be acquired.
>>
>> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
>> accelerator driver probing should be defferred vs failed. Provide that
>> indication via a new cxl_acquire_endpoint() API that can retrieve the
>> probe status of the memdev.
>>
>> The first consumer of this API is a test driver that excercises the CXL
>> Type-2 flow.
>>
>> Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
>>
>> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
>> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
>> ---
>>   drivers/cxl/core/memdev.c          | 41 ++++++++++++++++++++++++++++++
>>   drivers/cxl/core/port.c            |  2 +-
>>   drivers/cxl/mem.c                  |  7 +++--
>>   drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>>   include/linux/cxl_accel_mem.h      |  3 +++
>>   5 files changed, 59 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
>> index b902948b121f..d51c8bfb32e3 100644
>> --- a/drivers/cxl/core/memdev.c
>> +++ b/drivers/cxl/core/memdev.c
>> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>>   }
>>   EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>>   
>> +/*
>> + * Try to get a locked reference on a memdev's CXL port topology
>> + * connection. Be careful to observe when cxl_mem_probe() has deposited
>> + * a probe deferral awaiting the arrival of the CXL root driver
>> +*/
>> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
>> +{
>> +	struct cxl_port *endpoint;
>> +	int rc = -ENXIO;
>> +
>> +	device_lock(&cxlmd->dev);
>> +	endpoint = cxlmd->endpoint;
>> +	if (!endpoint)
>> +		goto err;
>> +
>> +	if (IS_ERR(endpoint)) {
>> +		rc = PTR_ERR(endpoint);
>> +		goto err;
>> +	}
>> +
>> +	device_lock(&endpoint->dev);
>> +	if (!endpoint->dev.driver)
>> +		goto err_endpoint;
>> +
>> +	return endpoint;
>> +
>> +err_endpoint:
>> +	device_unlock(&endpoint->dev);
>> +err:
>> +	device_unlock(&cxlmd->dev);
>> +	return ERR_PTR(rc);
>> +}
>> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
>> +
>> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint)
>> +{
>> +	device_unlock(&endpoint->dev);
>> +	device_unlock(&cxlmd->dev);
>> +}
>> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
>> +
>>   static void sanitize_teardown_notifier(void *data)
>>   {
>>   	struct cxl_memdev_state *mds = data;
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index d66c6349ed2d..3c6b896c5f65 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
>>   		 */
>>   		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>>   			dev_name(dport_dev));
>> -		return -ENXIO;
>> +		return -EPROBE_DEFER;
>>   	}
>>   
>>   	parent_port = find_cxl_port(dparent, &parent_dport);
>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
>> index f76af75a87b7..383a6f4829d3 100644
>> --- a/drivers/cxl/mem.c
>> +++ b/drivers/cxl/mem.c
>> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>>   		return rc;
>>   
>>   	rc = devm_cxl_enumerate_ports(cxlmd);
>> -	if (rc)
>> +	if (rc) {
>> +		cxlmd->endpoint = ERR_PTR(rc);
>>   		return rc;
>> +	}
>>   
>>   	parent_port = cxl_mem_find_port(cxlmd, &dport);
>>   	if (!parent_port) {
>>   		dev_err(dev, "CXL port topology not found\n");
>> -		return -ENXIO;
>> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
>> +		return -EPROBE_DEFER;
>>   	}
>>   
>>   	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM)) {
>> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
>> index 0abe66490ef5..2cf4837ddfc1 100644
>> --- a/drivers/net/ethernet/sfc/efx_cxl.c
>> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
>> @@ -65,8 +65,16 @@ void efx_cxl_init(struct efx_nic *efx)
>>   	}
>>   
>>   	cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds);
>> -	if (IS_ERR(cxl->cxlmd))
>> +	if (IS_ERR(cxl->cxlmd)) {
>>   		pci_info(pci_dev, "CXL accel memdev creation failed");
>> +		return;
>> +	}
>> +
>> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
>> +	if (IS_ERR(cxl->endpoint))
>> +		pci_info(pci_dev, "CXL accel acquire endpoint failed");
>> +
>> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
> there is no need to invoke cxl_release_endpoint() if cxl_acquire_endpoint() failed. right?
>
>

Right. BTW,  I do that in a following patch.

I should just add the functions to the CXL core here, and to use them in 
a subsequent patch where it makes sense.

Thanks


>>   }
>>   
>>   
>> diff --git a/include/linux/cxl_accel_mem.h b/include/linux/cxl_accel_mem.h
>> index 442ed9862292..701910021df8 100644
>> --- a/include/linux/cxl_accel_mem.h
>> +++ b/include/linux/cxl_accel_mem.h
>> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state *cxlds);
>>   
>>   struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>>   				       struct cxl_dev_state *cxlds);
>> +
>> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd);
>> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint);
>>   #endif
>

Fan Ni July 30, 2024, 4:43 p.m. UTC | #3

On Mon, Jul 15, 2024 at 06:28:28PM +0100, alejandro.lucero-palau@amd.com wrote:
> From: Alejandro Lucero <alucerop@amd.com>
> 
> The first stop for a CXL accelerator driver that wants to establish new
> CXL.mem regions is to register a 'struct cxl_memdev. That kicks off
> cxl_mem_probe() to enumerate all 'struct cxl_port' instances in the
> topology up to the root.
> 
> If the root driver has not attached yet the expectation is that the
> driver waits until that link is established. The common cxl_pci_driver
> has reason to keep the 'struct cxl_memdev' device attached to the bus
> until the root driver attaches. An accelerator may want to instead defer
> probing until CXL resources can be acquired.
> 
> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
> accelerator driver probing should be defferred vs failed. Provide that
> indication via a new cxl_acquire_endpoint() API that can retrieve the
> probe status of the memdev.
> 
> The first consumer of this API is a test driver that excercises the CXL
> Type-2 flow.
> 
> Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/core/memdev.c          | 41 ++++++++++++++++++++++++++++++
>  drivers/cxl/core/port.c            |  2 +-
>  drivers/cxl/mem.c                  |  7 +++--
>  drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>  include/linux/cxl_accel_mem.h      |  3 +++
>  5 files changed, 59 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index b902948b121f..d51c8bfb32e3 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>  
> +/*
> + * Try to get a locked reference on a memdev's CXL port topology
> + * connection. Be careful to observe when cxl_mem_probe() has deposited
> + * a probe deferral awaiting the arrival of the CXL root driver
> +*/
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_port *endpoint;
> +	int rc = -ENXIO;
> +
> +	device_lock(&cxlmd->dev);
> +	endpoint = cxlmd->endpoint;
> +	if (!endpoint)
> +		goto err;
> +
> +	if (IS_ERR(endpoint)) {
> +		rc = PTR_ERR(endpoint);
> +		goto err;
> +	}
> +
> +	device_lock(&endpoint->dev);
> +	if (!endpoint->dev.driver)
> +		goto err_endpoint;
> +
> +	return endpoint;
> +
> +err_endpoint:
> +	device_unlock(&endpoint->dev);
> +err:
> +	device_unlock(&cxlmd->dev);
> +	return ERR_PTR(rc);
> +}
> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
> +
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint)
> +{
> +	device_unlock(&endpoint->dev);
> +	device_unlock(&cxlmd->dev);
> +}
> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
> +
>  static void sanitize_teardown_notifier(void *data)
>  {
>  	struct cxl_memdev_state *mds = data;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index d66c6349ed2d..3c6b896c5f65 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
>  		 */
>  		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>  			dev_name(dport_dev));
> -		return -ENXIO;
> +		return -EPROBE_DEFER;
>  	}
>  
>  	parent_port = find_cxl_port(dparent, &parent_dport);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index f76af75a87b7..383a6f4829d3 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>  		return rc;
>  
>  	rc = devm_cxl_enumerate_ports(cxlmd);
> -	if (rc)
> +	if (rc) {
> +		cxlmd->endpoint = ERR_PTR(rc);
>  		return rc;
> +	}
>  
>  	parent_port = cxl_mem_find_port(cxlmd, &dport);
>  	if (!parent_port) {
>  		dev_err(dev, "CXL port topology not found\n");
> -		return -ENXIO;
> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
> +		return -EPROBE_DEFER;
>  	}
>  
>  	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM)) {
> diff --git a/drivers/net/ethernet/sfc/efx_cxl.c b/drivers/net/ethernet/sfc/efx_cxl.c
> index 0abe66490ef5..2cf4837ddfc1 100644
> --- a/drivers/net/ethernet/sfc/efx_cxl.c
> +++ b/drivers/net/ethernet/sfc/efx_cxl.c
> @@ -65,8 +65,16 @@ void efx_cxl_init(struct efx_nic *efx)
>  	}
>  
>  	cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds);
> -	if (IS_ERR(cxl->cxlmd))
> +	if (IS_ERR(cxl->cxlmd)) {
>  		pci_info(pci_dev, "CXL accel memdev creation failed");
pci_err()?
> +		return;
> +	}
> +
> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
> +	if (IS_ERR(cxl->endpoint))
> +		pci_info(pci_dev, "CXL accel acquire endpoint failed");
pci_err()?
> +
> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
>  }
>  
>  
> diff --git a/include/linux/cxl_accel_mem.h b/include/linux/cxl_accel_mem.h
> index 442ed9862292..701910021df8 100644
> --- a/include/linux/cxl_accel_mem.h
> +++ b/include/linux/cxl_accel_mem.h
> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state *cxlds);
>  
>  struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  				       struct cxl_dev_state *cxlds);
> +
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd);
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint);
>  #endif
> -- 
> 2.17.1
>

Jonathan Cameron Aug. 4, 2024, 5:41 p.m. UTC | #4

On Mon, 15 Jul 2024 18:28:28 +0100
<alejandro.lucero-palau@amd.com> wrote:

> From: Alejandro Lucero <alucerop@amd.com>
> 
> The first stop for a CXL accelerator driver that wants to establish new
> CXL.mem regions is to register a 'struct cxl_memdev. That kicks off
> cxl_mem_probe() to enumerate all 'struct cxl_port' instances in the
> topology up to the root.
> 
> If the root driver has not attached yet the expectation is that the
> driver waits until that link is established. The common cxl_pci_driver
> has reason to keep the 'struct cxl_memdev' device attached to the bus
> until the root driver attaches. An accelerator may want to instead defer
> probing until CXL resources can be acquired.
> 
> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
> accelerator driver probing should be defferred vs failed. Provide that
> indication via a new cxl_acquire_endpoint() API that can retrieve the
> probe status of the memdev.
> 
> The first consumer of this API is a test driver that excercises the CXL
Spell check.
exercises

> Type-2 flow.
> 
> Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/core/memdev.c          | 41 ++++++++++++++++++++++++++++++
>  drivers/cxl/core/port.c            |  2 +-
>  drivers/cxl/mem.c                  |  7 +++--
>  drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>  include/linux/cxl_accel_mem.h      |  3 +++
>  5 files changed, 59 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index b902948b121f..d51c8bfb32e3 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>  
> +/*
> + * Try to get a locked reference on a memdev's CXL port topology
> + * connection. Be careful to observe when cxl_mem_probe() has deposited
> + * a probe deferral awaiting the arrival of the CXL root driver

It might have deposited an error that isn't deferral I think.
I would be careful to make that clear in this comment.

> +*/
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_port *endpoint;
> +	int rc = -ENXIO;
> +
> +	device_lock(&cxlmd->dev);

I'd not really expect an 'acquire endpoint' to exit
in the good path with the cxlmd->dev device lock held.
Perhaps that needs a bit more shouting in the naming of
the function?

> +	endpoint = cxlmd->endpoint;
> +	if (!endpoint)
> +		goto err;
> +
> +	if (IS_ERR(endpoint)) {
> +		rc = PTR_ERR(endpoint);
> +		goto err;
> +	}
> +
> +	device_lock(&endpoint->dev);
> +	if (!endpoint->dev.driver)
> +		goto err_endpoint;
> +
> +	return endpoint;
> +
> +err_endpoint:
> +	device_unlock(&endpoint->dev);
> +err:
> +	device_unlock(&cxlmd->dev);
> +	return ERR_PTR(rc);
> +}
> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
> +
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint)
> +{
> +	device_unlock(&endpoint->dev);
> +	device_unlock(&cxlmd->dev);
> +}
> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
> +
>  static void sanitize_teardown_notifier(void *data)
>  {
>  	struct cxl_memdev_state *mds = data;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index d66c6349ed2d..3c6b896c5f65 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
>  		 */
>  		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>  			dev_name(dport_dev));
> -		return -ENXIO;
> +		return -EPROBE_DEFER;
>  	}
>  
>  	parent_port = find_cxl_port(dparent, &parent_dport);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index f76af75a87b7..383a6f4829d3 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>  		return rc;
>  
>  	rc = devm_cxl_enumerate_ports(cxlmd);
> -	if (rc)
> +	if (rc) {
> +		cxlmd->endpoint = ERR_PTR(rc);
>  		return rc;
> +	}
>  
>  	parent_port = cxl_mem_find_port(cxlmd, &dport);
>  	if (!parent_port) {
>  		dev_err(dev, "CXL port topology not found\n");

Hmm. This seems excessive error print for a deferred path.

> -		return -ENXIO;
> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
> +		return -EPROBE_DEFER;
>  	}
>  
>  	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM)) {

Zhi Wang Aug. 9, 2024, 2:40 p.m. UTC | #5

On Mon, 15 Jul 2024 18:28:28 +0100
<alejandro.lucero-palau@amd.com> wrote:

Another spell check is spotted besides others review threads. Will
circle back with more comments once checking the users of the APIs.

> From: Alejandro Lucero <alucerop@amd.com>
> 
> The first stop for a CXL accelerator driver that wants to establish
> new CXL.mem regions is to register a 'struct cxl_memdev. That kicks
> off cxl_mem_probe() to enumerate all 'struct cxl_port' instances in
> the topology up to the root.
> 
> If the root driver has not attached yet the expectation is that the
> driver waits until that link is established. The common cxl_pci_driver
> has reason to keep the 'struct cxl_memdev' device attached to the bus
> until the root driver attaches. An accelerator may want to instead
> defer probing until CXL resources can be acquired.
> 
> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
> accelerator driver probing should be defferred vs failed. Provide that
                                         ^deferred
> indication via a new cxl_acquire_endpoint() API that can retrieve the
> probe status of the memdev.
> 
> The first consumer of this API is a test driver that excercises the
> CXL Type-2 flow.
> 
> Based on
> https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/core/memdev.c          | 41
> ++++++++++++++++++++++++++++++ drivers/cxl/core/port.c            |
> 2 +- drivers/cxl/mem.c                  |  7 +++--
>  drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>  include/linux/cxl_accel_mem.h      |  3 +++
>  5 files changed, 59 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index b902948b121f..d51c8bfb32e3 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct
> device *host, }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>  
> +/*
> + * Try to get a locked reference on a memdev's CXL port topology
> + * connection. Be careful to observe when cxl_mem_probe() has
> deposited
> + * a probe deferral awaiting the arrival of the CXL root driver
> +*/
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_port *endpoint;
> +	int rc = -ENXIO;
> +
> +	device_lock(&cxlmd->dev);
> +	endpoint = cxlmd->endpoint;
> +	if (!endpoint)
> +		goto err;
> +
> +	if (IS_ERR(endpoint)) {
> +		rc = PTR_ERR(endpoint);
> +		goto err;
> +	}
> +
> +	device_lock(&endpoint->dev);
> +	if (!endpoint->dev.driver)
> +		goto err_endpoint;
> +
> +	return endpoint;
> +
> +err_endpoint:
> +	device_unlock(&endpoint->dev);
> +err:
> +	device_unlock(&cxlmd->dev);
> +	return ERR_PTR(rc);
> +}
> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
> +
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port
> *endpoint) +{
> +	device_unlock(&endpoint->dev);
> +	device_unlock(&cxlmd->dev);
> +}
> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
> +
>  static void sanitize_teardown_notifier(void *data)
>  {
>  	struct cxl_memdev_state *mds = data;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index d66c6349ed2d..3c6b896c5f65 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev
> *cxlmd, */
>  		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>  			dev_name(dport_dev));
> -		return -ENXIO;
> +		return -EPROBE_DEFER;
>  	}
>  
>  	parent_port = find_cxl_port(dparent, &parent_dport);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index f76af75a87b7..383a6f4829d3 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>  		return rc;
>  
>  	rc = devm_cxl_enumerate_ports(cxlmd);
> -	if (rc)
> +	if (rc) {
> +		cxlmd->endpoint = ERR_PTR(rc);
>  		return rc;
> +	}
>  
>  	parent_port = cxl_mem_find_port(cxlmd, &dport);
>  	if (!parent_port) {
>  		dev_err(dev, "CXL port topology not found\n");
> -		return -ENXIO;
> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
> +		return -EPROBE_DEFER;
>  	}
>  
>  	if (resource_size(&cxlds->pmem_res) &&
> IS_ENABLED(CONFIG_CXL_PMEM)) { diff --git
> a/drivers/net/ethernet/sfc/efx_cxl.c
> b/drivers/net/ethernet/sfc/efx_cxl.c index 0abe66490ef5..2cf4837ddfc1
> 100644 --- a/drivers/net/ethernet/sfc/efx_cxl.c +++
> b/drivers/net/ethernet/sfc/efx_cxl.c @@ -65,8 +65,16 @@ void
> efx_cxl_init(struct efx_nic *efx) }
>  
>  	cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds);
> -	if (IS_ERR(cxl->cxlmd))
> +	if (IS_ERR(cxl->cxlmd)) {
>  		pci_info(pci_dev, "CXL accel memdev creation
> failed");
> +		return;
> +	}
> +
> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
> +	if (IS_ERR(cxl->endpoint))
> +		pci_info(pci_dev, "CXL accel acquire endpoint
> failed"); +
> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
>  }
>  
>  
> diff --git a/include/linux/cxl_accel_mem.h
> b/include/linux/cxl_accel_mem.h index 442ed9862292..701910021df8
> 100644 --- a/include/linux/cxl_accel_mem.h
> +++ b/include/linux/cxl_accel_mem.h
> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state
> *cxlds); 
>  struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  				       struct cxl_dev_state *cxlds);
> +
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd);
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port
> *endpoint); #endif

Alejandro Lucero Palau Aug. 19, 2024, 1:54 p.m. UTC | #6

On 8/4/24 18:41, Jonathan Cameron wrote:
> On Mon, 15 Jul 2024 18:28:28 +0100
> <alejandro.lucero-palau@amd.com> wrote:
>
>> From: Alejandro Lucero <alucerop@amd.com>
>>
>> The first stop for a CXL accelerator driver that wants to establish new
>> CXL.mem regions is to register a 'struct cxl_memdev. That kicks off
>> cxl_mem_probe() to enumerate all 'struct cxl_port' instances in the
>> topology up to the root.
>>
>> If the root driver has not attached yet the expectation is that the
>> driver waits until that link is established. The common cxl_pci_driver
>> has reason to keep the 'struct cxl_memdev' device attached to the bus
>> until the root driver attaches. An accelerator may want to instead defer
>> probing until CXL resources can be acquired.
>>
>> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
>> accelerator driver probing should be defferred vs failed. Provide that
>> indication via a new cxl_acquire_endpoint() API that can retrieve the
>> probe status of the memdev.
>>
>> The first consumer of this API is a test driver that excercises the CXL
> Spell check.
> exercises


I'll fix it along with step instead of stop in the first line.


>> Type-2 flow.
>>
>> Based on https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
>>
>> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
>> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
>> ---
>>   drivers/cxl/core/memdev.c          | 41 ++++++++++++++++++++++++++++++
>>   drivers/cxl/core/port.c            |  2 +-
>>   drivers/cxl/mem.c                  |  7 +++--
>>   drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>>   include/linux/cxl_accel_mem.h      |  3 +++
>>   5 files changed, 59 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
>> index b902948b121f..d51c8bfb32e3 100644
>> --- a/drivers/cxl/core/memdev.c
>> +++ b/drivers/cxl/core/memdev.c
>> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>>   }
>>   EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>>   
>> +/*
>> + * Try to get a locked reference on a memdev's CXL port topology
>> + * connection. Be careful to observe when cxl_mem_probe() has deposited
>> + * a probe deferral awaiting the arrival of the CXL root driver
> It might have deposited an error that isn't deferral I think.
> I would be careful to make that clear in this comment.


Yes. The situation this patch is dealing with is not easy to handle. I 
realize the accel driver needs to be aware of it what the sfc code does 
not handle.

I need to work on this starting with emulating the situation and maybe 
adding the work as a test ... where we need some emulated Type2 device. 
Dan was asking about some work done before my initial RFC where Type2 
support in qemu was the target, maybe something we can talk about in the 
LPC.


>> +*/
>> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
>> +{
>> +	struct cxl_port *endpoint;
>> +	int rc = -ENXIO;
>> +
>> +	device_lock(&cxlmd->dev);
> I'd not really expect an 'acquire endpoint' to exit
> in the good path with the cxlmd->dev device lock held.
> Perhaps that needs a bit more shouting in the naming of
> the function?


Uhmm, not clear to me at this point if that is needed. This is basically 
the original patch by Dan so as said above, I need to work on this a bit 
further.

I'll try to get this sorted out for v3.

Thanks


>> +	endpoint = cxlmd->endpoint;
>> +	if (!endpoint)
>> +		goto err;
>> +
>> +	if (IS_ERR(endpoint)) {
>> +		rc = PTR_ERR(endpoint);
>> +		goto err;
>> +	}
>> +
>> +	device_lock(&endpoint->dev);
>> +	if (!endpoint->dev.driver)
>> +		goto err_endpoint;
>> +
>> +	return endpoint;
>> +
>> +err_endpoint:
>> +	device_unlock(&endpoint->dev);
>> +err:
>> +	device_unlock(&cxlmd->dev);
>> +	return ERR_PTR(rc);
>> +}
>> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
>> +
>> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port *endpoint)
>> +{
>> +	device_unlock(&endpoint->dev);
>> +	device_unlock(&cxlmd->dev);
>> +}
>> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
>> +
>>   static void sanitize_teardown_notifier(void *data)
>>   {
>>   	struct cxl_memdev_state *mds = data;
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index d66c6349ed2d..3c6b896c5f65 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev *cxlmd,
>>   		 */
>>   		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>>   			dev_name(dport_dev));
>> -		return -ENXIO;
>> +		return -EPROBE_DEFER;
>>   	}
>>   
>>   	parent_port = find_cxl_port(dparent, &parent_dport);
>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
>> index f76af75a87b7..383a6f4829d3 100644
>> --- a/drivers/cxl/mem.c
>> +++ b/drivers/cxl/mem.c
>> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>>   		return rc;
>>   
>>   	rc = devm_cxl_enumerate_ports(cxlmd);
>> -	if (rc)
>> +	if (rc) {
>> +		cxlmd->endpoint = ERR_PTR(rc);
>>   		return rc;
>> +	}
>>   
>>   	parent_port = cxl_mem_find_port(cxlmd, &dport);
>>   	if (!parent_port) {
>>   		dev_err(dev, "CXL port topology not found\n");
> Hmm. This seems excessive error print for a deferred path.
>
>> -		return -ENXIO;
>> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
>> +		return -EPROBE_DEFER;
>>   	}
>>   
>>   	if (resource_size(&cxlds->pmem_res) && IS_ENABLED(CONFIG_CXL_PMEM)) {

Zhi Wang Aug. 26, 2024, 5:42 p.m. UTC | #7

On Mon, 15 Jul 2024 18:28:28 +0100
<alejandro.lucero-palau@amd.com> wrote:

> From: Alejandro Lucero <alucerop@amd.com>
> 
> The first stop for a CXL accelerator driver that wants to establish
> new CXL.mem regions is to register a 'struct cxl_memdev. That kicks
> off cxl_mem_probe() to enumerate all 'struct cxl_port' instances in
> the topology up to the root.
> 
> If the root driver has not attached yet the expectation is that the
> driver waits until that link is established. The common cxl_pci_driver
> has reason to keep the 'struct cxl_memdev' device attached to the bus
> until the root driver attaches. An accelerator may want to instead
> defer probing until CXL resources can be acquired.
> 
> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
> accelerator driver probing should be defferred vs failed. Provide that
> indication via a new cxl_acquire_endpoint() API that can retrieve the
> probe status of the memdev.
> 
> The first consumer of this API is a test driver that excercises the
> CXL Type-2 flow.
> 

Out of curiosity, when and where do we probe CXL_DVSEC_CACHE_CAPABLE and
enable the CXL_DVSEC_CACHE_ENABLE bit for a type-2 device?

Thanks,
Zhi.

> Based on
> https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
> 
> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
> ---
>  drivers/cxl/core/memdev.c          | 41
> ++++++++++++++++++++++++++++++ drivers/cxl/core/port.c            |
> 2 +- drivers/cxl/mem.c                  |  7 +++--
>  drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>  include/linux/cxl_accel_mem.h      |  3 +++
>  5 files changed, 59 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
> index b902948b121f..d51c8bfb32e3 100644
> --- a/drivers/cxl/core/memdev.c
> +++ b/drivers/cxl/core/memdev.c
> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct
> device *host, }
>  EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>  
> +/*
> + * Try to get a locked reference on a memdev's CXL port topology
> + * connection. Be careful to observe when cxl_mem_probe() has
> deposited
> + * a probe deferral awaiting the arrival of the CXL root driver
> +*/
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
> +{
> +	struct cxl_port *endpoint;
> +	int rc = -ENXIO;
> +
> +	device_lock(&cxlmd->dev);
> +	endpoint = cxlmd->endpoint;
> +	if (!endpoint)
> +		goto err;
> +
> +	if (IS_ERR(endpoint)) {
> +		rc = PTR_ERR(endpoint);
> +		goto err;
> +	}
> +
> +	device_lock(&endpoint->dev);
> +	if (!endpoint->dev.driver)
> +		goto err_endpoint;
> +
> +	return endpoint;
> +
> +err_endpoint:
> +	device_unlock(&endpoint->dev);
> +err:
> +	device_unlock(&cxlmd->dev);
> +	return ERR_PTR(rc);
> +}
> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
> +
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port
> *endpoint) +{
> +	device_unlock(&endpoint->dev);
> +	device_unlock(&cxlmd->dev);
> +}
> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
> +
>  static void sanitize_teardown_notifier(void *data)
>  {
>  	struct cxl_memdev_state *mds = data;
> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
> index d66c6349ed2d..3c6b896c5f65 100644
> --- a/drivers/cxl/core/port.c
> +++ b/drivers/cxl/core/port.c
> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev
> *cxlmd, */
>  		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>  			dev_name(dport_dev));
> -		return -ENXIO;
> +		return -EPROBE_DEFER;
>  	}
>  
>  	parent_port = find_cxl_port(dparent, &parent_dport);
> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
> index f76af75a87b7..383a6f4829d3 100644
> --- a/drivers/cxl/mem.c
> +++ b/drivers/cxl/mem.c
> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>  		return rc;
>  
>  	rc = devm_cxl_enumerate_ports(cxlmd);
> -	if (rc)
> +	if (rc) {
> +		cxlmd->endpoint = ERR_PTR(rc);
>  		return rc;
> +	}
>  
>  	parent_port = cxl_mem_find_port(cxlmd, &dport);
>  	if (!parent_port) {
>  		dev_err(dev, "CXL port topology not found\n");
> -		return -ENXIO;
> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
> +		return -EPROBE_DEFER;
>  	}
>  
>  	if (resource_size(&cxlds->pmem_res) &&
> IS_ENABLED(CONFIG_CXL_PMEM)) { diff --git
> a/drivers/net/ethernet/sfc/efx_cxl.c
> b/drivers/net/ethernet/sfc/efx_cxl.c index 0abe66490ef5..2cf4837ddfc1
> 100644 --- a/drivers/net/ethernet/sfc/efx_cxl.c +++
> b/drivers/net/ethernet/sfc/efx_cxl.c @@ -65,8 +65,16 @@ void
> efx_cxl_init(struct efx_nic *efx) }
>  
>  	cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds);
> -	if (IS_ERR(cxl->cxlmd))
> +	if (IS_ERR(cxl->cxlmd)) {
>  		pci_info(pci_dev, "CXL accel memdev creation
> failed");
> +		return;
> +	}
> +
> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
> +	if (IS_ERR(cxl->endpoint))
> +		pci_info(pci_dev, "CXL accel acquire endpoint
> failed"); +
> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
>  }
>  
>  
> diff --git a/include/linux/cxl_accel_mem.h
> b/include/linux/cxl_accel_mem.h index 442ed9862292..701910021df8
> 100644 --- a/include/linux/cxl_accel_mem.h
> +++ b/include/linux/cxl_accel_mem.h
> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state
> *cxlds); 
>  struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>  				       struct cxl_dev_state *cxlds);
> +
> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd);
> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port
> *endpoint); #endif

Alejandro Lucero Palau Aug. 28, 2024, 1:43 p.m. UTC | #8

On 8/26/24 18:42, Zhi Wang wrote:
> On Mon, 15 Jul 2024 18:28:28 +0100
> <alejandro.lucero-palau@amd.com> wrote:
>
>> From: Alejandro Lucero <alucerop@amd.com>
>>
>> The first stop for a CXL accelerator driver that wants to establish
>> new CXL.mem regions is to register a 'struct cxl_memdev. That kicks
>> off cxl_mem_probe() to enumerate all 'struct cxl_port' instances in
>> the topology up to the root.
>>
>> If the root driver has not attached yet the expectation is that the
>> driver waits until that link is established. The common cxl_pci_driver
>> has reason to keep the 'struct cxl_memdev' device attached to the bus
>> until the root driver attaches. An accelerator may want to instead
>> defer probing until CXL resources can be acquired.
>>
>> Use the @endpoint attribute of a 'struct cxl_memdev' to convey when
>> accelerator driver probing should be defferred vs failed. Provide that
>> indication via a new cxl_acquire_endpoint() API that can retrieve the
>> probe status of the memdev.
>>
>> The first consumer of this API is a test driver that excercises the
>> CXL Type-2 flow.
>>
> Out of curiosity, when and where do we probe CXL_DVSEC_CACHE_CAPABLE and
> enable the CXL_DVSEC_CACHE_ENABLE bit for a type-2 device?
>
> Thanks,
> Zhi.


As It is mentioned in the cover letter, this is a Type2 device but not 
working on CXL.cache yet.

I hope we can discuss how to deal with CXL.cache in the LPC next month. 
I'll be talking about it and current state of this patchset.

Thank you


>> Based on
>> https://lore.kernel.org/linux-cxl/168592149709.1948938.8663425987110396027.stgit@dwillia2-xfh.jf.intel.com/T/#m18497367d2ae38f88e94c06369eaa83fa23e92b2
>>
>> Signed-off-by: Alejandro Lucero <alucerop@amd.com>
>> Co-developed-by: Dan Williams <dan.j.williams@intel.com>
>> ---
>>   drivers/cxl/core/memdev.c          | 41
>> ++++++++++++++++++++++++++++++ drivers/cxl/core/port.c            |
>> 2 +- drivers/cxl/mem.c                  |  7 +++--
>>   drivers/net/ethernet/sfc/efx_cxl.c | 10 +++++++-
>>   include/linux/cxl_accel_mem.h      |  3 +++
>>   5 files changed, 59 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/cxl/core/memdev.c b/drivers/cxl/core/memdev.c
>> index b902948b121f..d51c8bfb32e3 100644
>> --- a/drivers/cxl/core/memdev.c
>> +++ b/drivers/cxl/core/memdev.c
>> @@ -1137,6 +1137,47 @@ struct cxl_memdev *devm_cxl_add_memdev(struct
>> device *host, }
>>   EXPORT_SYMBOL_NS_GPL(devm_cxl_add_memdev, CXL);
>>   
>> +/*
>> + * Try to get a locked reference on a memdev's CXL port topology
>> + * connection. Be careful to observe when cxl_mem_probe() has
>> deposited
>> + * a probe deferral awaiting the arrival of the CXL root driver
>> +*/
>> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd)
>> +{
>> +	struct cxl_port *endpoint;
>> +	int rc = -ENXIO;
>> +
>> +	device_lock(&cxlmd->dev);
>> +	endpoint = cxlmd->endpoint;
>> +	if (!endpoint)
>> +		goto err;
>> +
>> +	if (IS_ERR(endpoint)) {
>> +		rc = PTR_ERR(endpoint);
>> +		goto err;
>> +	}
>> +
>> +	device_lock(&endpoint->dev);
>> +	if (!endpoint->dev.driver)
>> +		goto err_endpoint;
>> +
>> +	return endpoint;
>> +
>> +err_endpoint:
>> +	device_unlock(&endpoint->dev);
>> +err:
>> +	device_unlock(&cxlmd->dev);
>> +	return ERR_PTR(rc);
>> +}
>> +EXPORT_SYMBOL_NS(cxl_acquire_endpoint, CXL);
>> +
>> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port
>> *endpoint) +{
>> +	device_unlock(&endpoint->dev);
>> +	device_unlock(&cxlmd->dev);
>> +}
>> +EXPORT_SYMBOL_NS(cxl_release_endpoint, CXL);
>> +
>>   static void sanitize_teardown_notifier(void *data)
>>   {
>>   	struct cxl_memdev_state *mds = data;
>> diff --git a/drivers/cxl/core/port.c b/drivers/cxl/core/port.c
>> index d66c6349ed2d..3c6b896c5f65 100644
>> --- a/drivers/cxl/core/port.c
>> +++ b/drivers/cxl/core/port.c
>> @@ -1553,7 +1553,7 @@ static int add_port_attach_ep(struct cxl_memdev
>> *cxlmd, */
>>   		dev_dbg(&cxlmd->dev, "%s is a root dport\n",
>>   			dev_name(dport_dev));
>> -		return -ENXIO;
>> +		return -EPROBE_DEFER;
>>   	}
>>   
>>   	parent_port = find_cxl_port(dparent, &parent_dport);
>> diff --git a/drivers/cxl/mem.c b/drivers/cxl/mem.c
>> index f76af75a87b7..383a6f4829d3 100644
>> --- a/drivers/cxl/mem.c
>> +++ b/drivers/cxl/mem.c
>> @@ -145,13 +145,16 @@ static int cxl_mem_probe(struct device *dev)
>>   		return rc;
>>   
>>   	rc = devm_cxl_enumerate_ports(cxlmd);
>> -	if (rc)
>> +	if (rc) {
>> +		cxlmd->endpoint = ERR_PTR(rc);
>>   		return rc;
>> +	}
>>   
>>   	parent_port = cxl_mem_find_port(cxlmd, &dport);
>>   	if (!parent_port) {
>>   		dev_err(dev, "CXL port topology not found\n");
>> -		return -ENXIO;
>> +		cxlmd->endpoint = ERR_PTR(-EPROBE_DEFER);
>> +		return -EPROBE_DEFER;
>>   	}
>>   
>>   	if (resource_size(&cxlds->pmem_res) &&
>> IS_ENABLED(CONFIG_CXL_PMEM)) { diff --git
>> a/drivers/net/ethernet/sfc/efx_cxl.c
>> b/drivers/net/ethernet/sfc/efx_cxl.c index 0abe66490ef5..2cf4837ddfc1
>> 100644 --- a/drivers/net/ethernet/sfc/efx_cxl.c +++
>> b/drivers/net/ethernet/sfc/efx_cxl.c @@ -65,8 +65,16 @@ void
>> efx_cxl_init(struct efx_nic *efx) }
>>   
>>   	cxl->cxlmd = devm_cxl_add_memdev(&pci_dev->dev, cxl->cxlds);
>> -	if (IS_ERR(cxl->cxlmd))
>> +	if (IS_ERR(cxl->cxlmd)) {
>>   		pci_info(pci_dev, "CXL accel memdev creation
>> failed");
>> +		return;
>> +	}
>> +
>> +	cxl->endpoint = cxl_acquire_endpoint(cxl->cxlmd);
>> +	if (IS_ERR(cxl->endpoint))
>> +		pci_info(pci_dev, "CXL accel acquire endpoint
>> failed"); +
>> +	cxl_release_endpoint(cxl->cxlmd, cxl->endpoint);
>>   }
>>   
>>   
>> diff --git a/include/linux/cxl_accel_mem.h
>> b/include/linux/cxl_accel_mem.h index 442ed9862292..701910021df8
>> 100644 --- a/include/linux/cxl_accel_mem.h
>> +++ b/include/linux/cxl_accel_mem.h
>> @@ -29,4 +29,7 @@ int cxl_await_media_ready(struct cxl_dev_state
>> *cxlds);
>>   struct cxl_memdev *devm_cxl_add_memdev(struct device *host,
>>   				       struct cxl_dev_state *cxlds);
>> +
>> +struct cxl_port *cxl_acquire_endpoint(struct cxl_memdev *cxlmd);
>> +void cxl_release_endpoint(struct cxl_memdev *cxlmd, struct cxl_port
>> *endpoint); #endif

[v2,08/15] cxl: indicate probe deferral

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