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

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Date:   Tue, 8 Nov 2016 19:09:32 +0100
From:   Borislav Petkov <bp@...en8.de>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     linux-edac <linux-edac@...r.kernel.org>, X86 ML <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86/MCE: Remove MCP_TIMESTAMP

On Mon, Nov 07, 2016 at 06:37:50PM +0000, Luck, Tony wrote:
> Also to me ... and I think that's what used to happen (or at least was the
> intent).

How's that?

This still preserves the precise TSC timestamp in intel_threshold_interrupt().

---
From: Borislav Petkov <bp@...e.de>
Date: Tue, 8 Nov 2016 16:20:05 +0100
Subject: [PATCH] x86/MCE: Correct TSC timestamping of error records

We did have logic in the MCE code which would TSC-timestamp an error
record only when it is exact - i.e., it wasn't detected by polling. This
isn't the case anymore. So let's fix that:

We have a TSC timestamp in the error record only when it has been a
precise detection, i.e., either in the #MC handler or in one of the
interrupt handlers (thresholding, deferred, ...).

All other error records still have mce.time which contains the wall time
in order to be able to place the error record in time approximately.

Also, this fixes another bug where machine_check_poll() would clear
mce.tsc unconditionally even if we requested precise MCP_TIMESTAMP
logging.

Signed-off-by: Borislav Petkov <bp@...e.de>
Cc: Tony Luck <tony.luck@...el.com>
---
 arch/x86/kernel/cpu/mcheck/mce.c       | 3 +--
 arch/x86/kernel/cpu/mcheck/mce_intel.c | 4 ++--
 2 files changed, 3 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
index 4ca00474804b..b7a976d657f3 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));
@@ -1394,7 +1393,7 @@ 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..be0b2fad47c5 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);
@@ -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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