netdev - Re: [PATCH v8 04/27] cxl/pci: add check for validating capabilities

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Message-ID: <e38ec5a9-ff66-3c3f-b061-50ee07a8bdb0@amd.com>
Date: Fri, 27 Dec 2024 07:47:53 +0000
From: Alejandro Lucero Palau <alucerop@....com>
To: Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 alejandro.lucero-palau@....com
Cc: linux-cxl@...r.kernel.org, netdev@...r.kernel.org,
 dan.j.williams@...el.com, martin.habets@...inx.com, edward.cree@....com,
 davem@...emloft.net, kuba@...nel.org, pabeni@...hat.com,
 edumazet@...gle.com, dave.jiang@...el.com
Subject: Re: [PATCH v8 04/27] cxl/pci: add check for validating capabilities


On 12/24/24 17:15, Jonathan Cameron wrote:
> On Mon, 16 Dec 2024 16:10:19 +0000
> alejandro.lucero-palau@....com wrote:
>
>> From: Alejandro Lucero <alucerop@....com>
>>
>> During CXL device initialization supported capabilities by the device
>> are discovered. Type3 and Type2 devices have different mandatory
>> capabilities and a Type2 expects a specific set including optional
>> capabilities.
>>
>> Add a function for checking expected capabilities against those found
>> during initialization and allow those mandatory/expected capabilities to
>> be a subset of the capabilities found.
>>
>> Rely on this function for validating capabilities instead of when CXL
>> regs are probed.
>>
>> Signed-off-by: Alejandro Lucero <alucerop@....com>
>> Reviewed-by: Zhi Wang <zhiw@...dia.com>
> Some follow on comments in how to handle bitmaps.
>
> Jonathan
>
>
>> diff --git a/drivers/cxl/pci.c b/drivers/cxl/pci.c
>> index dbc1cd9bec09..1fcc53df1217 100644
>> --- a/drivers/cxl/pci.c
>> +++ b/drivers/cxl/pci.c
>> @@ -903,6 +903,8 @@ __ATTRIBUTE_GROUPS(cxl_rcd);
>>   static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>>   {
>>   	struct pci_host_bridge *host_bridge = pci_find_host_bridge(pdev->bus);
>> +	DECLARE_BITMAP(expected, CXL_MAX_CAPS);
>> +	DECLARE_BITMAP(found, CXL_MAX_CAPS);
>>   	struct cxl_memdev_state *mds;
>>   	struct cxl_dev_state *cxlds;
>>   	struct cxl_register_map map;
>> @@ -964,6 +966,28 @@ static int cxl_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
>>   	if (rc)
>>   		dev_dbg(&pdev->dev, "Failed to map RAS capability.\n");
>>   
>> +	bitmap_clear(expected, 0, CXL_MAX_CAPS);
>> +
>> +	/*
>> +	 * These are the mandatory capabilities for a Type3 device.
>> +	 * Only checking capabilities used by current Linux drivers.
>> +	 */
>> +	bitmap_set(expected, CXL_DEV_CAP_HDM, 1);
> set_bit()  - see comments in bitmap.h, these are fine applied to bitmaps
> and make more sense for setting a single bit.
>

OK.


>> +	bitmap_set(expected, CXL_DEV_CAP_DEV_STATUS, 1);
>> +	bitmap_set(expected, CXL_DEV_CAP_MAILBOX_PRIMARY, 1);
>> +	bitmap_set(expected, CXL_DEV_CAP_MEMDEV, 1);
>> +
>> +	/*
>> +	 * Checking mandatory caps are there as, at least, a subset of those
>> +	 * found.
>> +	 */
>> +	if (!cxl_pci_check_caps(cxlds, expected, found)) {
>> +		dev_err(&pdev->dev,
>> +			"Expected mandatory capabilities not found: (%08lx - %08lx)\n",
>> +			*expected, *found);
> There are printk formats for bitmaps that should be used here. %*pb
>

That is more convenient. I'll use them.

Thanks!


>
>> +		return -ENXIO;
>> +	}
>> +
>>   	rc = cxl_pci_type3_init_mailbox(cxlds);
>>   	if (rc)
>>   		return rc;
>> diff --git a/include/cxl/cxl.h b/include/cxl/cxl.h
>> index f656fcd4945f..05f06bfd2c29 100644
>> --- a/include/cxl/cxl.h
>> +++ b/include/cxl/cxl.h
>> @@ -37,4 +37,7 @@ void cxl_set_dvsec(struct cxl_dev_state *cxlds, u16 dvsec);
>>   void cxl_set_serial(struct cxl_dev_state *cxlds, u64 serial);
>>   int cxl_set_resource(struct cxl_dev_state *cxlds, struct resource res,
>>   		     enum cxl_resource);
>> +bool cxl_pci_check_caps(struct cxl_dev_state *cxlds,
>> +			unsigned long *expected_caps,
>> +			unsigned long *current_caps);
>>   #endif