Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752657AbbKYLty (ORCPT ); Wed, 25 Nov 2015 06:49:54 -0500 Received: from mail.skyhub.de ([78.46.96.112]:48834 "EHLO mail.skyhub.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752556AbbKYLtw (ORCPT ); Wed, 25 Nov 2015 06:49:52 -0500 Date: Wed, 25 Nov 2015 12:49:48 +0100 From: Borislav Petkov To: Hidehiro Kawai Cc: Jonathan Corbet , Peter Zijlstra , Ingo Molnar , "Eric W. Biederman" , "H. Peter Anvin" , Andrew Morton , Thomas Gleixner , Vivek Goyal , Baoquan He , linux-doc@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, Michal Hocko , Ingo Molnar , Masami Hiramatsu Subject: Re: [V5 PATCH 4/4] x86/apic: Introduce apic_extnmi boot option Message-ID: <20151125114948.GA4227@pd.tnic> References: <20151120093641.4285.97253.stgit@softrs> <20151120093650.4285.94971.stgit@softrs> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20151120093650.4285.94971.stgit@softrs> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5251 Lines: 160 On Fri, Nov 20, 2015 at 06:36:50PM +0900, Hidehiro Kawai wrote: > This patch introduces new boot option, apic_extnmi: > > apic_extnmi={ bsp | all | none} > > The default value is "bsp" and this is the current behavior; only > BSP receives external NMI. "all" allows external NMIs to be > broadcast to all CPUs. This would raise the success rate of panic > on NMI when BSP hangs up in NMI context or the external NMI is > swallowed by other NMI handlers on BSP. If you specified "none", > any CPUs don't receive external NMIs. This is useful for dump > capture kernel so that it wouldn't be shot down while saving a > crash dump. > > V5: > - Rename the option from "noextnmi" to "apic_extnmi" > - Add apic_extnmi=all feature > - Fix the wrong documentation about "noextnmi" (apic_extnmi=none) > > Signed-off-by: Hidehiro Kawai > Cc: Thomas Gleixner > Cc: Ingo Molnar > Cc: "H. Peter Anvin" > Cc: Jonathan Corbet > --- > Documentation/kernel-parameters.txt | 9 +++++++++ > arch/x86/include/asm/apic.h | 5 +++++ > arch/x86/kernel/apic/apic.c | 31 ++++++++++++++++++++++++++++++- > 3 files changed, 44 insertions(+), 1 deletion(-) > > diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt > index f8aae63..ceed3bc 100644 > --- a/Documentation/kernel-parameters.txt > +++ b/Documentation/kernel-parameters.txt > @@ -472,6 +472,15 @@ bytes respectively. Such letter suffixes can also be entirely omitted. > Change the amount of debugging information output > when initialising the APIC and IO-APIC components. > > + apic_extnmi= [APIC,X86] External NMI delivery setting > + Format: { bsp (default) | all | none } > + bsp: External NMI is delivered to only CPU 0 only to > + all: External NMIs are broadcast to all CPUs as a > + backup of CPU 0 > + none: External NMI is masked for all CPUs. This is > + useful so that a dump capture kernel won't be > + shot down by NMI > + > autoconf= [IPV6] > See Documentation/networking/ipv6.txt. > > diff --git a/arch/x86/include/asm/apic.h b/arch/x86/include/asm/apic.h > index 7f62ad4..c80f6b6 100644 > --- a/arch/x86/include/asm/apic.h > +++ b/arch/x86/include/asm/apic.h > @@ -23,6 +23,11 @@ > #define APIC_VERBOSE 1 > #define APIC_DEBUG 2 > > +/* Macros for apic_extnmi which controls external NMI masking */ > +#define APIC_EXTNMI_BSP 0 /* Default */ > +#define APIC_EXTNMI_ALL 1 > +#define APIC_EXTNMI_NONE 2 > + > /* > * Define the default level of output to be very little > * This can be turned up by using apic=verbose for more > diff --git a/arch/x86/kernel/apic/apic.c b/arch/x86/kernel/apic/apic.c > index 2f69e3b..a2a8074 100644 > --- a/arch/x86/kernel/apic/apic.c > +++ b/arch/x86/kernel/apic/apic.c > @@ -82,6 +82,12 @@ physid_mask_t phys_cpu_present_map; > static unsigned int disabled_cpu_apicid __read_mostly = BAD_APICID; > > /* > + * This variable controls which CPUs receive external NMIs. By default, > + * external NMIs are delivered to only BSP. only to the BSP. > + */ > +static int apic_extnmi = APIC_EXTNMI_BSP; > + > +/* > * Map cpu index to physical APIC ID > */ > DEFINE_EARLY_PER_CPU_READ_MOSTLY(u16, x86_cpu_to_apicid, BAD_APICID); > @@ -1161,6 +1167,8 @@ void __init init_bsp_APIC(void) > value = APIC_DM_NMI; > if (!lapic_is_integrated()) /* 82489DX */ > value |= APIC_LVT_LEVEL_TRIGGER; > + if (apic_extnmi == APIC_EXTNMI_NONE) > + value |= APIC_LVT_MASKED; > apic_write(APIC_LVT1, value); > } > > @@ -1380,7 +1388,8 @@ void setup_local_APIC(void) > /* > * only the BP should see the LINT1 NMI signal, obviously. > */ That comment needs adjusting. > - if (!cpu) > + if ((!cpu && apic_extnmi != APIC_EXTNMI_NONE) || > + apic_extnmi == APIC_EXTNMI_ALL) > value = APIC_DM_NMI; > else > value = APIC_DM_NMI | APIC_LVT_MASKED; > @@ -2548,3 +2557,23 @@ static int __init apic_set_disabled_cpu_apicid(char *arg) > return 0; > } > early_param("disable_cpu_apicid", apic_set_disabled_cpu_apicid); > + > +static int __init apic_set_extnmi(char *arg) > +{ > + if (!arg) > + return -EINVAL; > + > + if (strcmp("all", arg) == 0) if (!strncmp("all", arg, 3)) ditto for the rest > + apic_extnmi = APIC_EXTNMI_ALL; > + else if (strcmp("none", arg) == 0) > + apic_extnmi = APIC_EXTNMI_NONE; > + else if (strcmp("bsp", arg) == 0) > + apic_extnmi = APIC_EXTNMI_BSP; > + else { > + pr_warn("Unknown external NMI delivery mode `%s' is ignored\n", s/is // Also, if there's no other delivery mode which makes sense, you can do: pr_warn("Unknown external NMI delivery mode `%s', defaulting to 'bsp'\n", arg); apic_extnmi = APIC_EXTNMI_BSP; Btw, you can let the pr_warn line be longer than 80 cols. And if you don't default, you need return -EINVAL; here. -- Regards/Gruss, Boris. ECO tip #101: Trim your mails when you reply. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/