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Thu, 28 Apr 2022 05:18:51 +0000 (GMT) Message-ID: Date: Thu, 28 Apr 2022 10:48:50 +0530 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.7.0 Subject: Re: [PATCH v7 4/8] crash: add generic infrastructure for crash hotplug support Content-Language: en-US To: Baoquan He Cc: Eric DeVolder , linux-kernel@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, ebiederm@xmission.com, dyoung@redhat.com, vgoyal@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com, nramas@linux.microsoft.com, thomas.lendacky@amd.com, robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com, konrad.wilk@oracle.com, boris.ostrovsky@oracle.com References: <20220413164237.20845-1-eric.devolder@oracle.com> <20220413164237.20845-5-eric.devolder@oracle.com> <4eea2373-32f3-9960-cbec-21dc1a428807@oracle.com> <6f3a6cbb-0ac4-f178-fc17-18f9594da319@linux.ibm.com> From: Sourabh Jain In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-ORIG-GUID: K9S0Cu_gs1reU2aIDMDwL-8zQBsKh0PP X-Proofpoint-GUID: P6Y84sRNpSQ6v4vcUh7cMQR72Uucjzdy X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.858,Hydra:6.0.486,FMLib:17.11.64.514 definitions=2022-04-27_04,2022-04-27_01,2022-02-23_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 lowpriorityscore=0 mlxlogscore=999 clxscore=1015 priorityscore=1501 mlxscore=0 spamscore=0 adultscore=0 impostorscore=0 phishscore=0 suspectscore=0 malwarescore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2202240000 definitions=main-2204280031 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Baoquan, On 26/04/22 10:52, Baoquan He wrote: > On 04/26/22 at 09:36am, Sourabh Jain wrote: >> On 15/04/22 03:59, Eric DeVolder wrote: >>> Hi Baoquan, >>> Inline comments below. >>> Thanks! >>> eric >>> >>> On 4/13/22 21:45, Baoquan He wrote: >>>> On 04/13/22 at 12:42pm, Eric DeVolder wrote: >>>>> Upon CPU and memory changes, a generic crash_hotplug_handler() >>>>> dispatches the hot plug/unplug event to the architecture specific >>>>> arch_crash_hotplug_handler(). During the process, the kexec_mutex >>>>> is held. >>>>> >>>>> To support cpu hotplug, a callback is registered to capture the >>>>> CPUHP_AP_ONLINE_DYN online and ofline events via >>>>> cpuhp_setup_state_nocalls(). >>>>> >>>>> To support memory hotplug, a notifier is registered to capture the >>>>> MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier(). >>>>> >>>>> The cpu callback and memory notifier then call crash_hotplug_handler() >>>>> to handle the hot plug/unplug event. >>>>> >>>>> Signed-off-by: Eric DeVolder >>>>> --- >>>>>   include/linux/kexec.h |  16 +++++++ >>>>>   kernel/crash_core.c   | 101 >>>>> ++++++++++++++++++++++++++++++++++++++++++ >>>>>   2 files changed, 117 insertions(+) >>>>> >>>>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h >>>>> index f93f2591fc1e..02daff1f47dd 100644 >>>>> --- a/include/linux/kexec.h >>>>> +++ b/include/linux/kexec.h >>>>> @@ -306,6 +306,13 @@ struct kimage { >>>>>         /* Information for loading purgatory */ >>>>>       struct purgatory_info purgatory_info; >>>>> + >>>>> +#ifdef CONFIG_CRASH_HOTPLUG >>>>> +    bool hotplug_event; >>>>> +    unsigned int offlinecpu; >>>>> +    bool elfcorehdr_index_valid; >>>>> +    int elfcorehdr_index; >>>>> +#endif >>>>>   #endif >>>>>     #ifdef CONFIG_IMA_KEXEC >>>>> @@ -322,6 +329,15 @@ struct kimage { >>>>>       unsigned long elf_load_addr; >>>>>   }; >>>>>   +#ifdef CONFIG_CRASH_HOTPLUG >>>>> +void arch_crash_hotplug_handler(struct kimage *image, >>>>> +    unsigned int hp_action, unsigned int cpu); >>>>> +#define KEXEC_CRASH_HP_REMOVE_CPU   0 >>>>> +#define KEXEC_CRASH_HP_ADD_CPU      1 >>>>> +#define KEXEC_CRASH_HP_REMOVE_MEMORY 2 >>>>> +#define KEXEC_CRASH_HP_ADD_MEMORY   3 >>>>> +#endif /* CONFIG_CRASH_HOTPLUG */ >>>>> + >>>>>   /* kexec interface functions */ >>>>>   extern void machine_kexec(struct kimage *image); >>>>>   extern int machine_kexec_prepare(struct kimage *image); >>>>> diff --git a/kernel/crash_core.c b/kernel/crash_core.c >>>>> index 256cf6db573c..ecf746243ab2 100644 >>>>> --- a/kernel/crash_core.c >>>>> +++ b/kernel/crash_core.c >>>>> @@ -9,12 +9,17 @@ >>>>>   #include >>>>>   #include >>>>>   #include >>>>> +#include >>>>> +#include >>>>> +#include >>>>>     #include >>>>>   #include >>>>>     #include >>>>>   +#include "kexec_internal.h" >>>>> + >>>>>   /* vmcoreinfo stuff */ >>>>>   unsigned char *vmcoreinfo_data; >>>>>   size_t vmcoreinfo_size; >>>>> @@ -491,3 +496,99 @@ static int __init crash_save_vmcoreinfo_init(void) >>>>>   } >>>>>     subsys_initcall(crash_save_vmcoreinfo_init); >>>>> + >>>>> +#ifdef CONFIG_CRASH_HOTPLUG >>>>> +void __weak arch_crash_hotplug_handler(struct kimage *image, >>>>> +    unsigned int hp_action, unsigned int cpu) >>>>> +{ >>>>> +    pr_warn("crash hp: %s not implemented", __func__); >>>>> +} >>>>> + >>>>> +static void crash_hotplug_handler(unsigned int hp_action, >>>>> +    unsigned int cpu) >>>>> +{ >>>>> +    /* Obtain lock while changing crash information */ >>>>> +    if (!mutex_trylock(&kexec_mutex)) >>>>> +        return; >>>>> + >>>>> +    /* Check kdump is loaded */ >>>>> +    if (kexec_crash_image) { >>>>> +        pr_debug("crash hp: hp_action %u, cpu %u", hp_action, cpu); >>>>> + >>>>> +        /* Needed in order for the segments to be updated */ >>>>> +        arch_kexec_unprotect_crashkres(); >>>>> + >>>>> +        /* Flag to differentiate between normal load and hotplug */ >>>>> +        kexec_crash_image->hotplug_event = true; >>>>> + >>>>> +        /* Now invoke arch-specific update handler */ >>>>> +        arch_crash_hotplug_handler(kexec_crash_image, hp_action, cpu); >>>>> + >>>>> +        /* No longer handling a hotplug event */ >>>>> +        kexec_crash_image->hotplug_event = false; >>>>> + >>>>> +        /* Change back to read-only */ >>>>> +        arch_kexec_protect_crashkres(); >>>>> +    } >>>>> + >>>>> +    /* Release lock now that update complete */ >>>>> +    mutex_unlock(&kexec_mutex); >>>>> +} >>>>> + >>>>> +#if defined(CONFIG_MEMORY_HOTPLUG) >>>>> +static int crash_memhp_notifier(struct notifier_block *nb, >>>>> +    unsigned long val, void *v) >>>>> +{ >>>>> +    struct memory_notify *mhp = v; >>>>> + >>>>> +    switch (val) { >>>>> +    case MEM_ONLINE: >>>>> +        crash_hotplug_handler(KEXEC_CRASH_HP_ADD_MEMORY, -1U); >>>> We don't differentiate the memory add/remove, cpu add, except of cpu >>>> remove. Means the hp_action only differentiate cpu remove from the other >>>> action. Maybe only making two types? >>>> >>>> #define KEXEC_CRASH_HP_REMOVE_CPU   0 >>>> #define KEXEC_CRASH_HP_UPDATE_OTHER      1 >>>> >>> Sourabh Jain's work with PPC uses REMOVE_CPU, REMOVE_MEMORY, and >>> ADD_MEMORY. >>> Do you still want to consolidate these? >> On PowerPC different actions are needed for CPU add and memory add/remove. >> For CPU add case only FDT is updated whereas for the memory hotplug we will >> be >> updating FDT and elfcorehdr. > I don't understand. For elfcorehdr updating, we only need regenerate it. > Do you update them different for memory add/remove? We have different actions for cpu remove, CPU add and memory add/remove case. CPU remove: no action CPU add: update flattened device tree (FDT) memory add/remove: update FDT and regenerate/update elfcorehdr Since memory add/remove action is same we can have common hp_action for them. > > What I saw is the added action for memory hotplug is only for message > printing. Is this really needed? And memory hotplug is even not > supported. Please correct me if I missed anything. I agree that currently memory hp_action is only used for printing warning message but eventually we will be handling memory hotplug case as well. > + /* crash update on memory hotplug is not support yet */ > + if (hp_action == KEXEC_CRASH_HP_REMOVE_MEMORY || hp_action == KEXEC_CRASH_HP_ADD_MEMORY) { > + pr_info_once("crash hp: crash update is not supported with memory hotplug\n"); > + return; > + } Thanks, Sourabh Jain