linux-kernel - Re: "invalid agent type: 1" in acpi/ghes, cper: Recognize and cache CXL Protocol errors

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Message-ID: <5c052302-8639-41ef-9d51-3814f2778674@amd.com>
Date: Tue, 29 Jul 2025 08:52:19 -0700
From: "Koralahalli Channabasappa, Smita"
 <Smita.KoralahalliChannabasappa@....com>
To: Marc Herbert <marc.herbert@...ux.intel.com>, linux-efi@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-cxl@...r.kernel.org
Cc: Ard Biesheuvel <ardb@...nel.org>,
 Alison Schofield <alison.schofield@...el.com>,
 Vishal Verma <vishal.l.verma@...el.com>, Ira Weiny <ira.weiny@...el.com>,
 Dan Williams <dan.j.williams@...el.com>,
 Jonathan Cameron <Jonathan.Cameron@...wei.com>,
 Yazen Ghannam <yazen.ghannam@....com>, Terry Bowman <terry.bowman@....com>,
 Dave Jiang <dave.jiang@...el.com>, tony.luck@...el.com,
 Gregory Price <gourry@...rry.net>
Subject: Re: "invalid agent type: 1" in acpi/ghes, cper: Recognize and cache
 CXL Protocol errors

On 7/28/2025 10:41 PM, Marc Herbert wrote:
> On 2025-07-28 09:25, Koralahalli Channabasappa, Smita wrote:
> 
>> On 7/22/2025 12:24 PM, Marc Herbert wrote:
> 
>>>     The code below triggers the error "invalid agent type: 1" in Intel
>>> validation (internal issue 15018133056)
>>>
>>> It's not clear to anyone we asked why you did not include RCH_DP in
>>> the `switch (prot_err->agent_type)` in cxl_cper_post_prot_err() below.
>>>
>>> I can see how RCH_DP is special in cxl_cper_PRINT_prot_err() and I can
>>> even understand (despite my near-zero CPER knowledge) some of the
>>> special cases there. But in cxl_cper_post_prot_err() here, it's not
>>> clear why RCH_DP would be rejected. Could this be an oversight? If not,
>>> a comment with a short explanation would not hurt.
>>>
>>
>> You're right. RCH_DP was excluded because it doesn’t report a valid
>> SBDF in the CPER record. Instead, it provides only the RCRB base
>> address.
>>
>> I haven't thoroughly investigated whether SBDF can be reliably derived
>> from the RCRB base. There might be a platform-specific mechanism for
>> that, but at the time, it seemed non-trivial to implement. Introducing
>> additional infrastructure solely to support RCH_DP felt like it was
>> adding more complexity.
>>
>> I agree that a brief comment explaining this rationale would help. I'm
>> okay if you plan to include a fixup for this along with the one for
>> the device serial number.
> 
> If I understood you correctly, I think a different error message
> would be much better than a comment. Like this?

Yeah looks good to me. Thanks for fixing this!

Thanks
Smita

> 
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -730,6 +730,9 @@ static void cxl_cper_post_prot_err(struct cxl_cper_sec_prot_err *prot_err,
>   		memcpy(&wd.ras_cap, cap_start, sizeof(wd.ras_cap));
>   		wd.severity = cper_severity_to_aer(severity);
>   		break;
> +	case RCH_DP:
> +		pr_err_ratelimited("CXL CPER agent type unsupported: RCH_DP\n");
> +		return;
>   	default:
>   		pr_err_ratelimited("CXL CPER invalid agent type: %d\n",
>   				   prot_err->agent_type);