linux-kernel - Re: [PATCH v1 1/1] cxl/hdm: Verify HDM decoder capabilities after parsing

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Message-ID: <8ecd1237-4719-4f08-8826-2735eb6f472f@zohomail.com>
Date: Fri, 28 Feb 2025 10:48:29 +0800
From: Li Ming <ming.li@...omail.com>
To: Dave Jiang <dave.jiang@...el.com>
Cc: linux-cxl@...r.kernel.org, linux-kernel@...r.kernel.org,
 dave@...olabs.net, jonathan.cameron@...wei.com, alison.schofield@...el.com,
 vishal.l.verma@...el.com, ira.weiny@...el.com, dan.j.williams@...el.com
Subject: Re: [PATCH v1 1/1] cxl/hdm: Verify HDM decoder capabilities after
 parsing

On 2/27/2025 11:21 PM, Dave Jiang wrote:
>
> On 2/27/25 3:32 AM, Li Ming wrote:
>> devm_cxl_setup_hdm() only checks if decoder_count is 0 after parsing HDM
>> decoder capability, But according to the implementation of
>> cxl_hdm_decoder_count(), cxlhdm->decoder_count will never be 0.
>>
>> Per CXL specification, the values ranges of decoder_count and
>> target_count are limited. Adding a checking for the values of them
>> in case hardware initialized them with wrong values.
>>
>> Signed-off-by: Li Ming <ming.li@...omail.com>
>> ---
>> base-commit: 22eea823f69ae39dc060c4027e8d1470803d2e49 cxl/next
>> ---
>>  drivers/cxl/core/hdm.c | 31 ++++++++++++++++++++++++++++++-
>>  1 file changed, 30 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/cxl/core/hdm.c b/drivers/cxl/core/hdm.c
>> index 70cae4ebf8a4..a98191867c22 100644
>> --- a/drivers/cxl/core/hdm.c
>> +++ b/drivers/cxl/core/hdm.c
>> @@ -138,6 +138,34 @@ static bool should_emulate_decoders(struct cxl_endpoint_dvsec_info *info)
>>  	return true;
>>  }
>>  
>> +static int cxlhdm_decoder_caps_verify(struct cxl_hdm *cxlhdm)
>> +{
>> +	/*
>> +	 * CXL r3.2 section 8.2.4.20.1
>> +	 * CXL devices shall not advertise more than 10 decoders,
>> +	 * CXL switches and HBs may advertise up to 32 decoders.
>> +	 */
>> +	if (is_cxl_endpoint(cxlhdm->port) && cxlhdm->decoder_count > 10)
> #define the limit please

Will do, thanks.

>
>> +		return -EINVAL;
>> +	else if (cxlhdm->decoder_count > 32)
> same here
>
> DJ

Will do, thanks for review.


Ming

[snip]