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

[Mario Limonciello <superm1@kernel.org>]

On 3/15/26 8:14 AM, Borislav Petkov wrote:
> On Fri, Jan 23, 2026 at 03:30:56PM -0600, Mario Limonciello (AMD) wrote:
>> From: Yazen Ghannam <yazen.ghannam@amd.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.
> 
> Look what I said the last time:

FYI - you're replying to the v5 not the v6 [1].

Link: 
https://lore.kernel.org/all/20260307141024.819807-1-superm1@kernel.org/ [1]

> 
> https://lore.kernel.org/r/20260126130755.GIaXdnK65MTIiXqg-l@fat_crate.local
> 
> I'll have to teach AI to give feedback for commit messages explaining the
> diff.

Sorry about that one, I missed it even in v6.

> 
>> Signed-off-by: Yazen Ghannam <yazen.ghannam@amd.com>
>> Co-developed-by: "Mario Limonciello (AMD)" <superm1@kernel.org>
>> Signed-off-by: "Mario Limonciello (AMD)" <superm1@kernel.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)
>> +{
>> +	struct dmi_a_info *info = (struct dmi_a_info *)d;
>> +	void *next, *end;
>> +
>> +	/*
>> +	 * 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;
> 
>  From last time:
> 
> "This end needs to be corrected to some sane upper limit because we don't trust
> firmware one bit."
> 

I did add a check for info->count < 1, but that's not what you were 
actually looking for.  Do you have a suggestion for an upper limit to 
bound things?

I was thinking something like this:

#define DMI_LIMIT 10
int limit = info -> count > DMI_LIMIT ? DMI_LIMIT : info->count;
end  = (void *)info + limit * info->header.length;