From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753394AbeASGYh (ORCPT ); Fri, 19 Jan 2018 01:24:37 -0500 Received: from mail.cn.fujitsu.com ([183.91.158.132]:19769 "EHLO heian.cn.fujitsu.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750757AbeASGY2 (ORCPT ); Fri, 19 Jan 2018 01:24:28 -0500 X-IronPort-AV: E=Sophos;i="5.43,368,1503331200"; d="scan'208";a="35474318" Subject: Re: [RESEND PATCH 2/3] x86/apic/kexec: Enable legacy irq mode before jump to kexec/kdump kernel To: Baoquan He CC: , , , , , , , , , References: <1515123732-28908-1-git-send-email-bhe@redhat.com> <20180105043838.GK7235@x1> <250edc45-03be-76bd-4ce2-f6d7f90d0c4e@cn.fujitsu.com> <20180117100848.GF2321@localhost.localdomain> From: Dou Liyang Message-ID: Date: Fri, 19 Jan 2018 14:24:19 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.5.2 MIME-Version: 1.0 In-Reply-To: <20180117100848.GF2321@localhost.localdomain> Content-Type: text/plain; charset="gbk"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.167.226.106] X-yoursite-MailScanner-ID: 9433148AEA1B.AB0E8 X-yoursite-MailScanner: Found to be clean X-yoursite-MailScanner-From: douly.fnst@cn.fujitsu.com Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Baoquan, At 01/17/2018 06:08 PM, Baoquan He wrote: > On 01/17/18 at 05:47pm, Dou Liyang wrote: >> Hi Baoquan, >> >> At 01/05/2018 12:38 PM, Baoquan He wrote: >>> In commit >>> >>> commit 522e66464467 ("x86/apic: Disable I/O APIC before shutdown of the local APIC"). >>> >>> lapic_shutdown() invocation is moved after disable_IO_APIC(). In fact >>> in disable_IO_APIC(), it not only calls clear_IO_APIC() to disable >>> IO-APIC, also sets sets LAPIC and IO-APIC to make system be PIC or >>> Virtual wire mode. While the above commit putting disable_IO_APIC earlier >>> causes local APIC is completely disabled. So the legacy irq mode is >>> disabled too before jump to kexec/kdump kernel. >>> >> I have a question: >> >> As you said, Due to disable_IO_APIC() is triggered before >> lapic_shutdown(), So the interrupt virtual wire mode will be disabled. >> >> but, I found that: >> >> After machine_crash_shutdown() is executed, Linux will call >> machine_kexec(), and in machine_kexec(), disable_IO_APIC() will also be >> called again, why it can't switch to virtual wire mode successfully? Or >> is my understanding wrong? > The disable_IO_APIC() calling has a condition check, > > if (image->preserve_context) { > disable_IO_APIC(); > } > > For preserve_context case, it comes from kernel_kexec(). You can check > it in kexec man page, that is another scenario we use kexec for. But not > kexec and kdump. > Understood! This patch looks good to me and I also tested it, it's OK. Thanks, dou. >> >> +--------------+ >> | __crash_kexec| >> +--------------+ >> | >> | +-------------------------+ >> +--> | machine_crash_shutdown | >> | ++------------------------+ >> | | >> | | +-----------------+ >> | +> | disable_IO_APIC | >> | | +-----------------+ >> | | >> | | +----------------+ >> | +-^+ lapic_shutdown | >> | +----------------+ >> | >> | +-------------------------+ >> +--> | machine_kexec | >> | ++------------------------+ >> | | >> | | +-----------------+ >> | +> | disable_IO_APIC | >> | +-----------------+ >> | >> v >> >> Thanks, >> dou. >>> In normal kernel it defaults to be PIC mode or Virtual Wire mode during >>> system initialization before APIC mode is enabled and this is done by >>> BIOS initialization. But kexec/kdump kernel won't go through BIOS, so >>> we should set system as PIC or Virtual Wire mode before jump to kdump >>> kernel code directly. >>> >>> So let's take clear_IO_APIC out from disable_IO_APIC and rename >>> disable_IO_APIC as switch_to_legacy_irq_mode. Then only call clear_IO_APIC >>> when IO-APIC need be disabled. And call switch_to_legacy_irq_mode before >>> kexec/kdump jumping. >>> >>> Signed-off-by: Baoquan He >>> --- >>> arch/x86/include/asm/io_apic.h | 3 ++- >>> arch/x86/kernel/apic/io_apic.c | 12 ++++-------- >>> arch/x86/kernel/crash.c | 2 +- >>> arch/x86/kernel/machine_kexec_32.c | 15 +++++---------- >>> arch/x86/kernel/machine_kexec_64.c | 15 +++++---------- >>> arch/x86/kernel/reboot.c | 2 +- >>> 6 files changed, 18 insertions(+), 31 deletions(-) >>> >>> diff --git a/arch/x86/include/asm/io_apic.h b/arch/x86/include/asm/io_apic.h >>> index a8834dd546cd..e38ad3863a2c 100644 >>> --- a/arch/x86/include/asm/io_apic.h >>> +++ b/arch/x86/include/asm/io_apic.h >>> @@ -192,7 +192,8 @@ static inline unsigned int io_apic_read(unsigned int apic, unsigned int reg) >>> extern void setup_IO_APIC(void); >>> extern void enable_IO_APIC(void); >>> -extern void disable_IO_APIC(void); >>> +extern void clear_IO_APIC (void); >>> +extern void switch_to_legacy_irq_mode(void); >>> extern int IO_APIC_get_PCI_irq_vector(int bus, int devfn, int pin); >>> extern void print_IO_APICs(void); >>> #else /* !CONFIG_X86_IO_APIC */ >>> diff --git a/arch/x86/kernel/apic/io_apic.c b/arch/x86/kernel/apic/io_apic.c >>> index 8a7963421460..a47aa915d18c 100644 >>> --- a/arch/x86/kernel/apic/io_apic.c >>> +++ b/arch/x86/kernel/apic/io_apic.c >>> @@ -587,7 +587,7 @@ static void clear_IO_APIC_pin(unsigned int apic, unsigned int pin) >>> mpc_ioapic_id(apic), pin); >>> } >>> -static void clear_IO_APIC (void) >>> +void clear_IO_APIC (void) >>> { >>> int apic, pin; >>> @@ -1439,15 +1439,11 @@ void native_disable_io_apic(void) >>> } >>> /* >>> - * Not an __init, needed by the reboot code >>> + * Not an __init, needed by kexec/kdump code. >>> + * For safety IO-APIC and Local APIC need be cleared before this. >>> */ >>> -void disable_IO_APIC(void) >>> +void switch_to_legacy_irq_mode(void) >>> { >>> - /* >>> - * Clear the IO-APIC before rebooting: >>> - */ >>> - clear_IO_APIC(); >>> - >>> if (!nr_legacy_irqs()) >>> return; >>> diff --git a/arch/x86/kernel/crash.c b/arch/x86/kernel/crash.c >>> index 10e74d4778a1..318ffeaaf55a 100644 >>> --- a/arch/x86/kernel/crash.c >>> +++ b/arch/x86/kernel/crash.c >>> @@ -199,7 +199,7 @@ void native_machine_crash_shutdown(struct pt_regs *regs) >>> #ifdef CONFIG_X86_IO_APIC >>> /* Prevent crash_kexec() from deadlocking on ioapic_lock. */ >>> ioapic_zap_locks(); >>> - disable_IO_APIC(); >>> + clear_IO_APIC(); >>> #endif >>> lapic_shutdown(); >>> #ifdef CONFIG_HPET_TIMER >>> diff --git a/arch/x86/kernel/machine_kexec_32.c b/arch/x86/kernel/machine_kexec_32.c >>> index edfede768688..7ab10d930cc6 100644 >>> --- a/arch/x86/kernel/machine_kexec_32.c >>> +++ b/arch/x86/kernel/machine_kexec_32.c >>> @@ -190,18 +190,13 @@ void machine_kexec(struct kimage *image) >>> local_irq_disable(); >>> hw_breakpoint_disable(); >>> - if (image->preserve_context) { >>> #ifdef CONFIG_X86_IO_APIC >>> - /* >>> - * We need to put APICs in legacy mode so that we can >>> - * get timer interrupts in second kernel. kexec/kdump >>> - * paths already have calls to disable_IO_APIC() in >>> - * one form or other. kexec jump path also need >>> - * one. >>> - */ >>> - disable_IO_APIC(); >>> + /* >>> + * We need to put APICs in legacy mode so that we can >>> + * get timer interrupts in second kernel. >>> + */ >>> + switch_to_legacy_irq_mode(); >>> #endif >>> - } >>> control_page = page_address(image->control_code_page); >>> memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE); >>> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c >>> index 1f790cf9d38f..b5c0cbed6791 100644 >>> --- a/arch/x86/kernel/machine_kexec_64.c >>> +++ b/arch/x86/kernel/machine_kexec_64.c >>> @@ -288,18 +288,13 @@ void machine_kexec(struct kimage *image) >>> local_irq_disable(); >>> hw_breakpoint_disable(); >>> - if (image->preserve_context) { >>> #ifdef CONFIG_X86_IO_APIC >>> - /* >>> - * We need to put APICs in legacy mode so that we can >>> - * get timer interrupts in second kernel. kexec/kdump >>> - * paths already have calls to disable_IO_APIC() in >>> - * one form or other. kexec jump path also need >>> - * one. >>> - */ >>> - disable_IO_APIC(); >>> + /* >>> + * We need to put APICs in legacy mode so that we can >>> + * get timer interrupts in second kernel. >>> + */ >>> + switch_to_legacy_irq_mode(); >>> #endif >>> - } >>> control_page = page_address(image->control_code_page) + PAGE_SIZE; >>> memcpy(control_page, relocate_kernel, KEXEC_CONTROL_CODE_MAX_SIZE); >>> diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c >>> index 2126b9d27c34..b70cc0f38a29 100644 >>> --- a/arch/x86/kernel/reboot.c >>> +++ b/arch/x86/kernel/reboot.c >>> @@ -666,7 +666,7 @@ void native_machine_shutdown(void) >>> * Even without the erratum, it still makes sense to quiet IO APIC >>> * before disabling Local APIC. >>> */ >>> - disable_IO_APIC(); >>> + clear_IO_APIC(); >>> #endif >>> #ifdef CONFIG_SMP >>> >> >> > > >