Messages in this thread | | | Date | Fri, 6 Mar 2015 09:34:21 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v6] x86: mce: kexec: switch MCE handler for kexec/kdump |
| |
On Fri, Mar 06, 2015 at 02:59:13AM +0000, Naoya Horiguchi wrote: > From 8890e9976c525a4b480bf5f86008641688de8c11 Mon Sep 17 00:00:00 2001 > From: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com> > Date: Fri, 6 Mar 2015 11:52:10 +0900 > Subject: [PATCH v6] x86: mce: kexec: switch MCE handler for kexec/kdump > > kexec disables (or "shoots down") all CPUs other than a crashing CPU before > entering the 2nd kernel. But the MCE handler is still enabled after that, > so if MCE happens and broadcasts over the CPUs after the main thread starts > the 2nd kernel (which might not initialize MCE device yet, or might decide > not to enable it,) MCE handler runs only on the other CPUs (not on the main > thread,) leading to kernel panic with MCE synchronization. The user-visible > effect of this bug is kdump failure. > > Our standard MCE handler do_machine_check() assumes some about system's > status and it's hard to alter it to cover kexec/kdump context, so let's add > another kdump-specific one and switch to it. > > Note that this problem exists since current MCE handler was implemented in > 2.6.32, and recently commit 716079f66eac ("mce: Panic when a core has reached > a timeout") made it more visible by changing the default behavior of the > synchronization timeout from "ignore" to "panic". > > Signed-off-by: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
...
> +static void machine_check_under_kdump(struct pt_regs *regs, long error_code) > +{ > + struct mce m = {}; > + char *msg = NULL; > + char *nmsg = NULL; > + int i; > + int worst = 0; > + int severity; > + int ret;
if you do here
if (mce_cfg.disabled) return;
you can use the simple rdmsrl variants and not the _safe() ones with exception handling.
-- Regards/Gruss, Boris.
ECO tip #101: Trim your mails when you reply. --
| |