linux-kernel - Re: [PATCH v5 5/5] x86/CPU/AMD: Print the reason for the last reset

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Message-ID: <35bae46e-3b57-438a-a561-c93868120dcb@kernel.org>
Date: Wed, 30 Apr 2025 14:17:43 -0500
From: Mario Limonciello <superm1@...nel.org>
To: Borislav Petkov <bp@...en8.de>
Cc: Jean Delvare <jdelvare@...e.com>, Andi Shyti <andi.shyti@...nel.org>,
 Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>,
 Jonathan Corbet <corbet@....net>,
 Mario Limonciello <mario.limonciello@....com>,
 Yazen Ghannam <yazen.ghannam@....com>, Thomas Gleixner <tglx@...utronix.de>,
 Ingo Molnar <mingo@...hat.com>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)" <x86@...nel.org>,
 "H . Peter Anvin" <hpa@...or.com>,
 Shyam Sundar S K <Shyam-sundar.S-k@....com>,
 Hans de Goede <hdegoede@...hat.com>,
 "open list:DOCUMENTATION" <linux-doc@...r.kernel.org>,
 open list <linux-kernel@...r.kernel.org>,
 "open list:I2C/SMBUS CONTROLLER DRIVERS FOR PC" <linux-i2c@...r.kernel.org>,
 "open list:AMD PMC DRIVER" <platform-driver-x86@...r.kernel.org>
Subject: Re: [PATCH v5 5/5] x86/CPU/AMD: Print the reason for the last reset

On 4/30/2025 2:10 PM, Borislav Petkov wrote:
> On Wed, Apr 30, 2025 at 02:05:44PM -0500, Mario Limonciello wrote:
>> On 4/30/2025 2:03 PM, Borislav Petkov wrote:
>>> On Tue, Apr 22, 2025 at 06:48:30PM -0500, Mario Limonciello wrote:
>>>> +	/* Iterate on each bit in the 'value' mask: */
>>>> +	while (true) {
>>>> +		bit = find_next_bit(&value, BITS_PER_LONG, bit + 1);
>>>> +
>>>> +		/* Reached the end of the word, no more bits: */
>>>> +		if (bit >= BITS_PER_LONG) {
>>>> +			if (!nr_reasons)
>>>> +				pr_info("x86/amd: Previous system reset reason [0x%08lx]: Unknown\n", value);
>>>> +			break;
>>>> +		}
>>>> +
>>>> +		if (!s5_reset_reason_txt[bit])
>>>> +			continue;
>>>> +
>>>> +		nr_reasons++;
>>>> +		pr_info("x86/amd: Previous system reset reason [0x%08lx]: %s\n",
>>>> +			value, s5_reset_reason_txt[bit]);
>>>> +	}
>>>
>>> What happened to that simpler idea:
>>>
>>> https://lore.kernel.org/r/20250411125050.GEZ_kQKtYBfEMDQuXU@fat_crate.local
>>>
>>
>> This one was more advantageous in that if multiple bits were set for any
>> reason we could get messages for all of them printed.
> 
> I don't understand - you dump an array element for every bit now too...
> 

Well with that approach once you got a known bit set you broke the loop 
and would print a message for that known bit.  But if you have two bits 
set you either need another loop or you only get one message print.