On Thu, Jun 28, 2018 at 11:07:22AM +0900, gregkh@xxxxxxxxxxxxxxxxxxx wrote:
>
> The patch below does not apply to the 4.4-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@xxxxxxxxxxxxxxx>.
>
> thanks,
This patch relies on:
3acb431b84d8 ("x86/mce: Detect local MCEs properly")
cherry pick that (and fix up the trivial merge problem around the
change to initialize "lmce = 1;" instead of "lmce = 0";)
Then this will merge cleanly.
-Tony
>
> ------------------ original commit in Linus's tree ------------------
>
> From 40c36e2741d7fe1e66d6ec55477ba5fd19c9c5d2 Mon Sep 17 00:00:00 2001
> From: Tony Luck <tony.luck@xxxxxxxxx>
> Date: Fri, 22 Jun 2018 11:54:23 +0200
> Subject: [PATCH] x86/mce: Fix incorrect "Machine check from unknown source"
> message
>
> Some injection testing resulted in the following console log:
>
> mce: [Hardware Error]: CPU 22: Machine Check Exception: f Bank 1: bd80000000100134
> mce: [Hardware Error]: RIP 10:<ffffffffc05292dd> {pmem_do_bvec+0x11d/0x330 [nd_pmem]}
> mce: [Hardware Error]: TSC c51a63035d52 ADDR 3234bc4000 MISC 88
> mce: [Hardware Error]: PROCESSOR 0:50654 TIME 1526502199 SOCKET 0 APIC 38 microcode 2000043
> mce: [Hardware Error]: Run the above through 'mcelog --ascii'
> Kernel panic - not syncing: Machine check from unknown source
>
> This confused everybody because the first line quite clearly shows
> that we found a logged error in "Bank 1", while the last line says
> "unknown source".
>
> The problem is that the Linux code doesn't do the right thing
> for a local machine check that results in a fatal error.
>
> It turns out that we know very early in the handler whether the
> machine check is fatal. The call to mce_no_way_out() has checked
> all the banks for the CPU that took the local machine check. If
> it says we must crash, we can do so right away with the right
> messages.
>
> We do scan all the banks again. This means that we might initially
> not see a problem, but during the second scan find something fatal.
> If this happens we print a slightly different message (so I can
> see if it actually every happens).
>
> [ bp: Remove unneeded severity assignment. ]
>
> Signed-off-by: Tony Luck <tony.luck@xxxxxxxxx>
> Signed-off-by: Borislav Petkov <bp@xxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
> Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
> Cc: Qiuxu Zhuo <qiuxu.zhuo@xxxxxxxxx>
> Cc: linux-edac <linux-edac@xxxxxxxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx # 4.2
> Link: http://lkml.kernel.org/r/52e049a497e86fd0b71c529651def8871c804df0.1527283897.git.tony.luck@xxxxxxxxx
>
> diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c
> index 7e6f51a9d917..e93670d736a6 100644
> --- a/arch/x86/kernel/cpu/mcheck/mce.c
> +++ b/arch/x86/kernel/cpu/mcheck/mce.c
> @@ -1207,13 +1207,18 @@ void do_machine_check(struct pt_regs *regs, long error_code)
> lmce = m.mcgstatus & MCG_STATUS_LMCES;
>
> /*
> + * Local machine check may already know that we have to panic.
> + * Broadcast machine check begins rendezvous in mce_start()
> * Go through all banks in exclusion of the other CPUs. This way we
> * don't report duplicated events on shared banks because the first one
> - * to see it will clear it. If this is a Local MCE, then no need to
> - * perform rendezvous.
> + * to see it will clear it.
> */
> - if (!lmce)
> + if (lmce) {
> + if (no_way_out)
> + mce_panic("Fatal local machine check", &m, msg);
> + } else {
> order = mce_start(&no_way_out);
> + }
>
> for (i = 0; i < cfg->banks; i++) {
> __clear_bit(i, toclear);
> @@ -1289,12 +1294,17 @@ void do_machine_check(struct pt_regs *regs, long error_code)
> no_way_out = worst >= MCE_PANIC_SEVERITY;
> } else {
> /*
> - * Local MCE skipped calling mce_reign()
> - * If we found a fatal error, we need to panic here.
> + * If there was a fatal machine check we should have
> + * already called mce_panic earlier in this function.
> + * Since we re-read the banks, we might have found
> + * something new. Check again to see if we found a
> + * fatal error. We call "mce_severity()" again to
> + * make sure we have the right "msg".
> */
> - if (worst >= MCE_PANIC_SEVERITY && mca_cfg.tolerant < 3)
> - mce_panic("Machine check from unknown source",
> - NULL, NULL);
> + if (worst >= MCE_PANIC_SEVERITY && mca_cfg.tolerant < 3) {
> + mce_severity(&m, cfg->tolerant, &msg, true);
> + mce_panic("Local fatal machine check!", &m, msg);
> + }
> }
>
> /*
>
