From 97ffb7a107905c62cb658f319876ae170833d9e4 Mon Sep 17 00:00:00 2001
From: Borislav Petkov <bp@alien8.de>
Date: Mon, 23 Aug 2021 17:31:29 -0700
Subject: [PATCH] x86/mce: Defer processing of early errors
Git-commit: 3bff147b187d5dfccfca1ee231b0761a89f1eff5
Patch-mainline: v5.15-rc1
References: stable-5.14.4
[ Upstream commit 3bff147b187d5dfccfca1ee231b0761a89f1eff5 ]
When a fatal machine check results in a system reset, Linux does not
clear the error(s) from machine check bank(s) - hardware preserves the
machine check banks across a warm reset.
During initialization of the kernel after the reboot, Linux reads, logs,
and clears all machine check banks.
But there is a problem. In:
5de97c9f6d85 ("x86/mce: Factor out and deprecate the /dev/mcelog driver")
the call to mce_register_decode_chain() moved later in the boot
sequence. This means that /dev/mcelog doesn't see those early error
logs.
This was partially fixed by:
cd9c57cad3fe ("x86/MCE: Dump MCE to dmesg if no consumers")
which made sure that the logs were not lost completely by printing
to the console. But parsing console logs is error prone. Users of
/dev/mcelog should expect to find any early errors logged to standard
places.
Add a new flag MCP_QUEUE_LOG to machine_check_poll() to be used in early
machine check initialization to indicate that any errors found should
just be queued to genpool. When mcheck_late_init() is called it will
call mce_schedule_work() to actually log and flush any errors queued in
the genpool.
[ Based on an original patch, commit message by and completely
productized by Tony Luck. ]
Fixes: 5de97c9f6d85 ("x86/mce: Factor out and deprecate the /dev/mcelog driver")
Reported-by: Sumanth Kamatala <skamatala@juniper.net>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Tony Luck <tony.luck@intel.com>
Link: https://lkml.kernel.org/r/20210824003129.GA1642753@agluck-desk2.amr.corp.intel.com
Signed-off-by: Sasha Levin <sashal@kernel.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
arch/x86/include/asm/mce.h | 1 +
arch/x86/kernel/cpu/mce/core.c | 11 ++++++++---
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/mce.h b/arch/x86/include/asm/mce.h
index 0607ec4f5091..da9321548f6f 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_QUEUE_LOG = BIT(3), /* only queue to genpool */
};
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..8cb7816d03b4 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_QUEUE_LOG)
+ 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_QUEUE_LOG | m_fl, &all_banks);
cr4_set_bits(X86_CR4_MCE);
--
2.26.2