linux-kernel - Re: [PATCH v5 5/5] x86/CPU/AMD: Print AGESA string from DMI additional information entry

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Message-ID: <3c3f850b-0acb-4238-8cfc-498496b230a4@kernel.org>
Date: Mon, 26 Jan 2026 09:15:58 -0600
From: "Mario Limonciello (AMD) (kernel.org)" <superm1@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Yazen Ghannam <yazen.ghannam@....com>, Jean Delvare <jdelvare@...e.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 5/5] x86/CPU/AMD: Print AGESA string from DMI
 additional information entry



On 1/26/2026 7:07 AM, Borislav Petkov wrote:
> On Fri, Jan 23, 2026 at 03:30:56PM -0600, Mario Limonciello (AMD) wrote:
>> From: Yazen Ghannam <yazen.ghannam@....com>
>>
>> Type 40 entries (Additional Information) are summarized in section 7.41
>> as part of the SMBIOS specification.  Generally, these entries aren't
>> interesting to save.
>>
>> However on some AMD Zen systems, the AGESA version is stored here. This
>> is useful to save to the kernel message logs for debugging. It can be
>> used to cross-reference issues.
>>
>> Implement an iterator for the Additional Information entries. Use this
>> to find and print the AGESA string. Do so in AMD code, since the use
>> case is AMD-specific.
> 
> Please do not explain the diff.
> 
👍
>> Signed-off-by: Yazen Ghannam <yazen.ghannam@....com>
>> Co-developed-by: "Mario Limonciello (AMD)" <superm1@...nel.org>
>> Signed-off-by: "Mario Limonciello (AMD)" <superm1@...nel.org>
>> ---
>> v5:
>>   * Return "" in !CONFIG_DMI case (LKP robot, Yazen)
>> v4:
>>   * New patch (based upon older versions though)
>> ---
>>   arch/x86/kernel/cpu/amd.c   | 53 +++++++++++++++++++++++++++++++++++++
>>   drivers/firmware/dmi_scan.c |  3 ++-
>>   include/linux/dmi.h         | 18 +++++++++++++
>>   3 files changed, 73 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c
>> index bc94ff1e250ad..aa04a27aeb107 100644
>> --- a/arch/x86/kernel/cpu/amd.c
>> +++ b/arch/x86/kernel/cpu/amd.c
>> @@ -1,6 +1,7 @@
>>   // SPDX-License-Identifier: GPL-2.0-only
>>   #include <linux/export.h>
>>   #include <linux/bitops.h>
>> +#include <linux/dmi.h>
>>   #include <linux/elf.h>
>>   #include <linux/mm.h>
>>   #include <linux/kvm_types.h>
>> @@ -1404,3 +1405,55 @@ static __init int print_s5_reset_status_mmio(void)
>>   	return 0;
>>   }
>>   late_initcall(print_s5_reset_status_mmio);
>> +
>> +static void __init amd_dmi_scan_additional(const struct dmi_header *d, void *p)
> 
> It's a static - no need for the "amd_" prefix.
> 
>> +{
>> +	struct dmi_a_info *info = (struct dmi_a_info *)d;
>> +	void *next, *end;
> 
> This needs a
> 
> 	if (!IS_ENABLED(CONFIG_DMI))
> 		return;
> 
👍
>> +
>> +	/*
>> +	 * DMI Additional Info table has a 'count' field. But it's not very
>> +	 * helpful since the entries are variable length. So don't use it.
>> +	 */
>> +	if (info->header.type != DMI_ENTRY_ADDITIONAL ||
>> +	    info->header.length < DMI_A_INFO_MIN_SIZE)
>> +		return;
>> +
>> +	/*
>> +	 * Get the first entry.
>> +	 * The minimum table size guarantees at least one entry is present.
>> +	 */
>> +	next = (void *)(info + 1);
>> +	end  = (void *)info + info->header.length;
> 
> This end needs to be corrected to some sane upper limit because we don't trust
> firmware one bit.
> 
👍
>> +
>> +	do {
>> +		struct dmi_a_info_entry *entry;
>> +		const char *string_ptr;
>> +
>> +		entry = (struct dmi_a_info_entry *)next;
>> +
>> +		/*
>> +		 * Not much can be done to validate data. At least the entry
>> +		 * length shouldn't be 0.
>> +		 */
>> +		if (!entry->length)
>> +			return;
>> +
>> +		string_ptr = dmi_string_nosave(&info->header, entry->str_num);
>> +
>> +		/* Only one AGESA string is expected. */
> 
> Superfluous comment.

👍
> 
>> +		if (!strncmp(string_ptr, "AGESA", 5)) {
>> +			pr_info("%s\n", string_ptr);
> 
> So on this Zen5 laptop here, this dumps:
> 
> [    0.840480] AGESA!V9 StrixPI-FP8 1.0.0.1d
> 
> I guess we can make that:
> 
> [    0.840480] AGESA: V9 StrixPI-FP8 1.0.0.1d
> 
> no?

I think if slicing and dicing the string I would instead have us "match" 
"AGESA!V9" instead and then spit it out like this:

AGESA: StrixPI-FP8 1.0.0.1d

Then if there's a v10 sentinel some day or something like that we would 
add a new match then.