linux-kernel - [PATCH] x86/MCE: Remove MCP

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Date:   Sat, 5 Nov 2016 14:11:04 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     Tony Luck <tony.luck@...el.com>
Cc:     linux-edac <linux-edac@...r.kernel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: [PATCH] x86/MCE: Remove MCP_TIMESTAMP

Whoops,

one more:

---
From: Borislav Petkov <bp@...e.de>
Date: Sat, 5 Nov 2016 12:47:03 +0100
Subject: [PATCH] x86/MCE: Remove MCP_TIMESTAMP

MCP_TIMESTAMP controls whether current TSC value should be added to
the MCE record. Most of machine_check_poll() callers supply it, except
__mcheck_cpu_init_generic() but this is wrong because we could be
logging an MCE right at the same time and thus log one without the TSC
value.

What is more, machine_check_poll() did unconditionally clear mce.tsc
which is another bug.

So, get rid of all that and simply log an MCE with a TSC value always.
Simplifies the code a bit too.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Tony Luck <tony.luck@...el.com>
---
 arch/x86/include/asm/mce.h             | 5 ++---
 arch/x86/kernel/cpu/mcheck/mce.c       | 6 +-----
 arch/x86/kernel/cpu/mcheck/mce_intel.c | 6 +++---
 3 files changed, 6 insertions(+), 11 deletions(-)

diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 748b8da8e627..3b53c260e0be 100644
--- a/arch/x86/include/asm/mce.h
+++ b/arch/x86/include/asm/mce.h
@@ -265,9 +265,8 @@ typedef DECLARE_BITMAP(mce_banks_t, MAX_NR_BANKS);
 DECLARE_PER_CPU(mce_banks_t, mce_poll_banks);
 
 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_UC		= BIT(0),	/* log uncorrected errors */
+	MCP_DONTLOG	= BIT(1),	/* only clear, don't log */
 };
 bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b);
 
diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 4ca00474804b..82564156d6ab 100644
--- a/arch/x86/kernel/cpu/mcheck/mce.c
+++ b/arch/x86/kernel/cpu/mcheck/mce.c
@@ -713,7 +713,6 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 		m.misc = 0;
 		m.addr = 0;
 		m.bank = i;
-		m.tsc = 0;
 
 		barrier();
 		m.status = mce_rdmsrl(msr_ops.status(i));
@@ -735,9 +734,6 @@ bool machine_check_poll(enum mcp_flags flags, mce_banks_t *b)
 
 		mce_read_aux(&m, i);
 
-		if (!(flags & MCP_TIMESTAMP))
-			m.tsc = 0;
-
 		severity = mce_severity(&m, mca_cfg.tolerant, NULL, false);
 
 		if (severity == MCE_DEFERRED_SEVERITY && memory_error(&m))
@@ -1394,7 +1390,7 @@ static void mce_timer_fn(unsigned long data)
 	iv = __this_cpu_read(mce_next_interval);
 
 	if (mce_available(this_cpu_ptr(&cpu_info))) {
-		machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_poll_banks));
+		machine_check_poll(0, this_cpu_ptr(&mce_poll_banks));
 
 		if (mce_intel_cmci_poll()) {
 			iv = mce_adjust_timer(iv);
diff --git a/arch/x86/kernel/cpu/mcheck/mce_intel.c b/arch/x86/kernel/cpu/mcheck/mce_intel.c
index 1defb8ea882c..3262f0d726bb 100644
--- a/arch/x86/kernel/cpu/mcheck/mce_intel.c
+++ b/arch/x86/kernel/cpu/mcheck/mce_intel.c
@@ -130,7 +130,7 @@ bool mce_intel_cmci_poll(void)
 	 * Reset the counter if we've logged an error in the last poll
 	 * during the storm.
 	 */
-	if (machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned)))
+	if (machine_check_poll(0, this_cpu_ptr(&mce_banks_owned)))
 		this_cpu_write(cmci_backoff_cnt, INITIAL_CHECK_INTERVAL);
 	else
 		this_cpu_dec(cmci_backoff_cnt);
@@ -250,7 +250,7 @@ static void intel_threshold_interrupt(void)
 	if (cmci_storm_detect())
 		return;
 
-	machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
+	machine_check_poll(0, this_cpu_ptr(&mce_banks_owned));
 }
 
 /*
@@ -342,7 +342,7 @@ void cmci_recheck(void)
 		return;
 
 	local_irq_save(flags);
-	machine_check_poll(MCP_TIMESTAMP, this_cpu_ptr(&mce_banks_owned));
+	machine_check_poll(0, this_cpu_ptr(&mce_banks_owned));
 	local_irq_restore(flags);
 }
 
-- 
2.10.0

-- 
Regards/Gruss,
    Boris.

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