linux-kernel - Re: [PATCH v4] vmcoreinfo: Track and log recoverable hardware errors

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Message-ID: <85663f65-d746-4e2c-b8a6-d594d9d0ba42@intel.com>
Date: Fri, 1 Aug 2025 07:52:17 -0700
From: Dave Hansen <dave.hansen@...el.com>
To: Breno Leitao <leitao@...ian.org>, "Rafael J. Wysocki"
 <rafael@...nel.org>, Len Brown <lenb@...nel.org>,
 James Morse <james.morse@....com>, Tony Luck <tony.luck@...el.com>,
 Borislav Petkov <bp@...en8.de>, Robert Moore <robert.moore@...el.com>,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>,
 Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
 "H. Peter Anvin" <hpa@...or.com>, Hanjun Guo <guohanjun@...wei.com>,
 Mauro Carvalho Chehab <mchehab@...nel.org>,
 Mahesh J Salgaonkar <mahesh@...ux.ibm.com>,
 Oliver O'Halloran <oohall@...il.com>, Bjorn Helgaas <bhelgaas@...gle.com>
Cc: linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
 acpica-devel@...ts.linux.dev, osandov@...ndov.com,
 xueshuai@...ux.alibaba.com, konrad.wilk@...cle.com,
 linux-edac@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
 linux-pci@...r.kernel.org, kernel-team@...a.com, osandov@...com
Subject: Re: [PATCH v4] vmcoreinfo: Track and log recoverable hardware errors

On 8/1/25 05:31, Breno Leitao wrote:
> Introduce a generic infrastructure for tracking recoverable hardware
> errors (HW errors that are visible to the OS but does not cause a panic)
> and record them for vmcore consumption.
...

Are there patches for the consumer side of this, too? Or do humans
looking at crash dumps have to know what to go digging for?

In either case, don't we need documentation for this new ABI?

> diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
> index 4da4eab56c81d..f85759453f89a 100644
> --- a/arch/x86/kernel/cpu/mce/core.c
> +++ b/arch/x86/kernel/cpu/mce/core.c
> @@ -45,6 +45,7 @@
>  #include <linux/task_work.h>
>  #include <linux/hardirq.h>
>  #include <linux/kexec.h>
> +#include <linux/vmcore_info.h>
>  
>  #include <asm/fred.h>
>  #include <asm/cpu_device_id.h>
> @@ -1690,6 +1691,9 @@ noinstr void do_machine_check(struct pt_regs *regs)
>  	}
>  
>  out:
> +	/* Given it didn't panic, mark it as recoverable */
> +	hwerr_log_error_type(HWERR_RECOV_MCE);
> +

Does "MCE" mean anything outside of x86?

I wonder if this would be better left as "HWERR_RECOV_ARCH" or something.

...
> +void hwerr_log_error_type(enum hwerr_error_type src)
> +{
> +	if (src < 0 || src >= HWERR_RECOV_MAX)
> +		return;
> +
> +	/* No need to atomics/locks given the precision is not important */

Sure, but it's not even more lines of code to do:

	atomic_inc(&hwerr_data[src].count);
	WRITE_ONCE(hwerr_data[src].timestamp, ktime_get_real_seconds());

So why not?

> +	hwerr_data[src].count++;
> +	hwerr_data[src].timestamp = ktime_get_real_seconds();
> +}
> +EXPORT_SYMBOL_GPL(hwerr_log_error_type);

I'd also love to hear more about _actual_ users of this. Surely, someone
hit a real world problem and thought this would be a nifty solution. Who
was that? What problem did they hit? How does this help them?