linux-kernel - Re: [PATCH 4/9] x86/mce: Move machine_check_poll() status checks to helper functions

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Message-ID: <20240726140030.GA193170@yaz-khff2.amd.com>
Date: Fri, 26 Jul 2024 10:00:30 -0400
From: Yazen Ghannam <yazen.ghannam@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
	tony.luck@...el.com, x86@...nel.org, avadhut.naik@....com,
	john.allen@....com
Subject: Re: [PATCH 4/9] x86/mce: Move machine_check_poll() status checks to
 helper functions

On Mon, Jun 03, 2024 at 07:37:27PM +0200, Borislav Petkov wrote:
> On Thu, May 23, 2024 at 10:56:36AM -0500, Yazen Ghannam wrote:
> > @@ -709,48 +747,9 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
> >  		if (!mca_cfg.cmci_disabled)
> >  			mce_track_storm(&m);
> >  
> > -		/* If this entry is not valid, ignore it */
> > -		if (!(m.status & MCI_STATUS_VAL))
> > +		if (!log_poll_error(flags, &m))
> >  			continue;
> >  
> > -		/*
> > -		 * If we are logging everything (at CPU online) or this
> > -		 * is a corrected error, then we must log it.
> > -		 */
> > -		if ((flags & MCP_UC) || !(m.status & MCI_STATUS_UC))
> > -			goto log_it;
> > -
> > -		/*
> > -		 * Newer Intel systems that support software error
> > -		 * recovery need to make additional checks. Other
> > -		 * CPUs should skip over uncorrected errors, but log
> > -		 * everything else.
> > -		 */
> 
> You lost that comment.
> 

Sorry, will keep it.

> > -		if (!mca_cfg.ser) {
> > -			if (m.status & MCI_STATUS_UC)
> > -				continue;
> > -			goto log_it;
> > -		}
> > -
> > -		/* Log "not enabled" (speculative) errors */
> > -		if (!(m.status & MCI_STATUS_EN))
> > -			goto log_it;
> > -
> > -		/*
> > -		 * Log UCNA (SDM: 15.6.3 "UCR Error Classification")
> > -		 * UC == 1 && PCC == 0 && S == 0
> > -		 */
> > -		if (!(m.status & MCI_STATUS_PCC) && !(m.status & MCI_STATUS_S))
> > -			goto log_it;
> > -
> > -		/*
> > -		 * Skip anything else. Presumption is that our read of this
> > -		 * bank is racing with a machine check. Leave the log alone
> > -		 * for do_machine_check() to deal with it.
> > -		 */
> > -		continue;
> > -
> > -log_it:
> >  		if (flags & MCP_DONTLOG)
> >  			goto clear_it;
> 
> Btw, the code looks really weird now:
> 
>                 if (!log_poll_error(flags, &m))
>                         continue;
> 
>                 if (flags & MCP_DONTLOG)
>                         goto clear_it;
> 
> i.e.,
> 
> 1. Should I log it?
> 
> 2. Should I not log it?
> 
> Oh well, it was like that before logically so...
>

We can rename the new function and add comments. What do you think of
the change below?

Thanks,
Yazen

@@ -797,9 +797,11 @@ void machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
		if (!mca_cfg.cmci_disabled)
			mce_track_storm(&m);

-               if (!log_poll_error(flags, &m, &status_reg))
+               /* Verify that the error should be logged based on hardware conditions. */
+               if (!loggable_poll_error(flags, &m, &status_reg))
			continue;

+               /* Clear a loggable error, e.g., one leftover from boot time. */
		if (flags & MCP_DONTLOG)
			goto clear_it;