| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <20070305122011.GA16133@elte.hu> Date: Mon, 5 Mar 2007 13:20:11 +0100 From: Ingo Molnar <mingo@...e.hu> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Andi Kleen <ak@...e.de>, Andrew Morton <akpm@...ux-foundation.org>, linux-kernel@...r.kernel.org, Arjan van de Ven <arjan@...radead.org>, Adrian Bunk <bunk@...sta.de>, Alan Cox <alan@...rguk.ukuu.org.uk>, Arjan van de Ven <arjan@...radead.org> Subject: [patch] disable NMI watchdog by default Linus, Andrew sent the patch below (which is now months old and has been in -mm for some time) towards Andi's tree 4 weeks ago, but apparently it fell into a black hole there - the patch is still not upstream! This is a must-have for v2.6.21, because the problem still triggers even with the latest upstream tree, if i boot a KVM guest. Frankly, i find it ridiculous that i had to write more than 10 emails about this stupid topic already, while i'm the original author of this feature to begin with. The "do not enable by default debug features that break certain systems" concept is obvious to me. This category of regressions has been introduced by Andi when he made the NMI watchdog the default in certain scenarios at around v2.6.18 - over my repeated objections. Andi Cc:-ed :-) Ingo ----- Forwarded message from Ingo Molnar <mingo@...e.hu> ----- From: Ingo Molnar <mingo@...e.hu> Subject: [patch] disable NMI watchdog by default there's a new NMI watchdog related problem: KVM crashes on certain bzImages because ... we enable the NMI watchdog by default (even if the user does not ask for it) , and no other OS on this planet does that so KVM doesnt have emulation for that yet. So KVM injects a #GP, which crashes the Linux guest: general protection fault: 0000 [#1] PREEMPT SMP Modules linked in: CPU: 0 EIP: 0060:[<c011a8ae>] Not tainted VLI EFLAGS: 00000246 (2.6.20-rc5-rt0 #3) EIP is at setup_apic_nmi_watchdog+0x26d/0x3d3 and no, i did /not/ request an nmi_watchdog on the boot command line! Solution: turn off that darn thing! It's a debug tool, not a 'make life harder' tool!! with this patch the KVM guest boots up just fine. And with this my laptop (Lenovo T60) also stopped its sporadic hard hanging (sometimes in acpi_init(), sometimes later during bootup, sometimes much later during actual use) as well. It hung with both nmi_watchdog=1 and nmi_watchdog=2, so it's generally the fact of NMI injection that is causing problems, not the NMI watchdog variant, nor any particular bootup code. The patch is unintrusive. Signed-off-by: Ingo Molnar <mingo@...e.hu> Index: linux/include/asm-i386/nmi.h =================================================================== --- linux.orig/include/asm-i386/nmi.h +++ linux/include/asm-i386/nmi.h @@ -33,7 +33,7 @@ extern int nmi_watchdog_tick (struct pt_ extern atomic_t nmi_active; extern unsigned int nmi_watchdog; -#define NMI_DEFAULT -1 +#define NMI_DEFAULT 0 #define NMI_NONE 0 #define NMI_IO_APIC 1 #define NMI_LOCAL_APIC 2 Index: linux/include/asm-x86_64/nmi.h =================================================================== --- linux.orig/include/asm-x86_64/nmi.h +++ linux/include/asm-x86_64/nmi.h @@ -63,7 +63,7 @@ extern int setup_nmi_watchdog(char *); extern atomic_t nmi_active; extern unsigned int nmi_watchdog; -#define NMI_DEFAULT -1 +#define NMI_DEFAULT 0 #define NMI_NONE 0 #define NMI_IO_APIC 1 #define NMI_LOCAL_APIC 2 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists