linux-kernel - Re: [PATCH v2] x86/mce: Defer processing early errors until mcheck_late

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Message-ID: <YSQKT0NPrx6puVUQ@zn.tnic>
Date:   Mon, 23 Aug 2021 22:51:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     x86@...nel.org, linux-edac@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Sumanth Kamatala <skamatala@...iper.net>
Subject: Re: [PATCH v2] x86/mce: Defer processing early errors until
 mcheck_late_init()

On Mon, Aug 23, 2021 at 01:41:22PM -0700, Luck, Tony wrote:
>  arch/x86/kernel/cpu/mce/core.c | 6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)

I actually had a different idea in mind, considering the fact that some
machinery to only log the early MCEs is already there. And this fits
more naturally in the flow and doesn't need a bool switch.

Hmmm?

---
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 0607ec4f5091..9b13cca74f65 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -265,6 +265,7 @@ enum mcp_flags {
 	MCP_TIMESTAMP	= BIT(0),	/* log time stamp */
 	MCP_UC		= BIT(1),	/* log uncorrected errors */
 	MCP_DONTLOG	= BIT(2),	/* only clear, don't log */
+	MCP_LOG_ONLY	= BIT(3),	/* log only */
 };
 bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
 
diff --git a/arch/x86/kernel/cpu/mce/core.c b/arch/x86/kernel/cpu/mce/core.c
index 22791aadc085..bb691503c2e4 100644
--- a/arch/x86/kernel/cpu/mce/core.c
+++ b/arch/x86/kernel/cpu/mce/core.c
@@ -817,7 +817,10 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 		if (mca_cfg.dont_log_ce && !mce_usable_address(&m))
 			goto clear_it;
 
-		mce_log(&m);
+		if (flags & MCP_LOG_ONLY)
+			mce_gen_pool_add(&m);
+		else
+			mce_log(&m);
 
 clear_it:
 		/*
@@ -1639,10 +1642,12 @@ static void __mcheck_cpu_init_generic(void)
 		m_fl = MCP_DONTLOG;
 
 	/*
-	 * Log the machine checks left over from the previous reset.
+	 * Log the machine checks left over from the previous reset. Log them
+	 * only, do not start processing them. That will happen in mcheck_late_init()
+	 * when all consumers have been registered on the notifier chain.
 	 */
 	bitmap_fill(all_banks, MAX_NR_BANKS);
-	machine_check_poll(MCP_UC | m_fl, &all_banks);
+	machine_check_poll(MCP_UC | MCP_LOG_ONLY | m_fl, &all_banks);
 
 	cr4_set_bits(X86_CR4_MCE);
 

-- 
Regards/Gruss,
    Boris.

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