lkml.org 
[lkml]   [2023]   [Apr]   [11]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH v5 2/2] ACPI: APEI: handle synchronous exceptions in task work
    Date
    Hardware errors could be signaled by synchronous interrupt, e.g.  when an
    error is detected by a background scrubber, or signaled by synchronous
    exception, e.g. when an uncorrected error is consumed. Both synchronous and
    asynchronous error are queued and handled by a dedicated kthread in
    workqueue.

    commit 7f17b4a121d0 ("ACPI: APEI: Kick the memory_failure() queue for
    synchronous errors") keep track of whether memory_failure() work was
    queued, and make task_work pending to flush out the workqueue so that the
    work for synchronous error is processed before returning to user-space.
    The trick ensures that the corrupted page is unmapped and poisoned. And
    after returning to user-space, the task starts at current instruction which
    triggering a page fault in which kernel will send SIGBUS to current process
    due to VM_FAULT_HWPOISON.

    However, the memory failure recovery for hwpoison-aware mechanisms does not
    work as expected. For example, hwpoison-aware user-space processes like
    QEMU register their customized SIGBUS handler and enable early kill mode by
    seting PF_MCE_EARLY at initialization. Then the kernel will directy notify
    the process by sending a SIGBUS signal in memory failure with wrong
    si_code: the actual user-space process accessing the corrupt memory
    location, but its memory failure work is handled in a kthread context, so
    it will send SIGBUS with BUS_MCEERR_AO si_code to the actual user-space
    process instead of BUS_MCEERR_AR in kill_proc().

    To this end, separate synchronous and asynchronous error handling into
    different paths like X86 platform does:

    - valid synchronous errors: queue a task_work to synchronously send SIGBUS
    before ret_to_user.
    - valid asynchronous errors: queue a work into workqueue to asynchronously
    handle memory failure.
    - abnormal branches such as invalid PA, unexpected severity, no memory
    failure config support, invalid GUID section, OOM, etc.

    Then for valid synchronous errors, the current context in memory failure is
    exactly belongs to the task consuming poison data and it will send SIBBUS
    with proper si_code.

    Fixes: 7f17b4a121d0 ("ACPI: APEI: Kick the memory_failure() queue for synchronous errors")
    Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
    Tested-by: Ma Wupeng <mawupeng1@huawei.com>
    ---
    drivers/acpi/apei/ghes.c | 91 +++++++++++++++++++++++++++-------------
    include/acpi/ghes.h | 3 --
    mm/memory-failure.c | 13 ------
    3 files changed, 61 insertions(+), 46 deletions(-)

    diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
    index c479b85899f5..4b70955e25f9 100644
    --- a/drivers/acpi/apei/ghes.c
    +++ b/drivers/acpi/apei/ghes.c
    @@ -452,28 +452,51 @@ static void ghes_clear_estatus(struct ghes *ghes,
    }

    /*
    - * Called as task_work before returning to user-space.
    - * Ensure any queued work has been done before we return to the context that
    - * triggered the notification.
    + * struct sync_task_work - for synchronous RAS event
    + *
    + * @twork: callback_head for task work
    + * @pfn: page frame number of corrupted page
    + * @flags: fine tune action taken
    + *
    + * Structure to pass task work to be handled before
    + * ret_to_user via task_work_add().
    */
    -static void ghes_kick_task_work(struct callback_head *head)
    +struct sync_task_work {
    + struct callback_head twork;
    + u64 pfn;
    + int flags;
    +};
    +
    +static void memory_failure_cb(struct callback_head *twork)
    {
    - struct acpi_hest_generic_status *estatus;
    - struct ghes_estatus_node *estatus_node;
    - u32 node_len;
    + int ret;
    + struct sync_task_work *twcb =
    + container_of(twork, struct sync_task_work, twork);

    - estatus_node = container_of(head, struct ghes_estatus_node, task_work);
    - if (IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))
    - memory_failure_queue_kick(estatus_node->task_work_cpu);
    + ret = memory_failure(twcb->pfn, twcb->flags);
    + kfree(twcb);

    - estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
    - node_len = GHES_ESTATUS_NODE_LEN(cper_estatus_len(estatus));
    - gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node, node_len);
    + if (!ret)
    + return;
    +
    + /*
    + * -EHWPOISON from memory_failure() means that it already sent SIGBUS
    + * to the current process with the proper error info,
    + * -EOPNOTSUPP means hwpoison_filter() filtered the error event,
    + *
    + * In both cases, no further processing is required.
    + */
    + if (ret == -EHWPOISON || ret == -EOPNOTSUPP)
    + return;
    +
    + pr_err("Memory error not recovered");
    + force_sig(SIGBUS);
    }

    static bool ghes_do_memory_failure(u64 physical_addr, int flags)
    {
    unsigned long pfn;
    + struct sync_task_work *twcb;

    if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))
    return false;
    @@ -486,6 +509,18 @@ static bool ghes_do_memory_failure(u64 physical_addr, int flags)
    return false;
    }

    + if (flags == MF_ACTION_REQUIRED && current->mm) {
    + twcb = kmalloc(sizeof(*twcb), GFP_ATOMIC);
    + if (!twcb)
    + return false;
    +
    + twcb->pfn = pfn;
    + twcb->flags = flags;
    + init_task_work(&twcb->twork, memory_failure_cb);
    + task_work_add(current, &twcb->twork, TWA_RESUME);
    + return true;
    + }
    +
    memory_failure_queue(pfn, flags);
    return true;
    }
    @@ -1000,9 +1035,8 @@ static void ghes_proc_in_irq(struct irq_work *irq_work)
    struct ghes_estatus_node *estatus_node;
    struct acpi_hest_generic *generic;
    struct acpi_hest_generic_status *estatus;
    - bool task_work_pending;
    + bool queued, sync;
    u32 len, node_len;
    - int ret;

    llnode = llist_del_all(&ghes_estatus_llist);
    /*
    @@ -1015,27 +1049,25 @@ static void ghes_proc_in_irq(struct irq_work *irq_work)
    estatus_node = llist_entry(llnode, struct ghes_estatus_node,
    llnode);
    estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
    + sync = is_hest_sync_notify(estatus_node->ghes);
    len = cper_estatus_len(estatus);
    node_len = GHES_ESTATUS_NODE_LEN(len);
    - task_work_pending = ghes_do_proc(estatus_node->ghes, estatus);
    +
    + queued = ghes_do_proc(estatus_node->ghes, estatus);
    + /*
    + * If no memory failure work is queued for abnormal synchronous
    + * errors, do a force kill.
    + */
    + if (sync && !queued)
    + force_sig(SIGBUS);
    +
    if (!ghes_estatus_cached(estatus)) {
    generic = estatus_node->generic;
    if (ghes_print_estatus(NULL, generic, estatus))
    ghes_estatus_cache_add(generic, estatus);
    }
    -
    - if (task_work_pending && current->mm) {
    - estatus_node->task_work.func = ghes_kick_task_work;
    - estatus_node->task_work_cpu = smp_processor_id();
    - ret = task_work_add(current, &estatus_node->task_work,
    - TWA_RESUME);
    - if (ret)
    - estatus_node->task_work.func = NULL;
    - }
    -
    - if (!estatus_node->task_work.func)
    - gen_pool_free(ghes_estatus_pool,
    - (unsigned long)estatus_node, node_len);
    + gen_pool_free(ghes_estatus_pool, (unsigned long)estatus_node,
    + node_len);

    llnode = next;
    }
    @@ -1096,7 +1128,6 @@ static int ghes_in_nmi_queue_one_entry(struct ghes *ghes,

    estatus_node->ghes = ghes;
    estatus_node->generic = ghes->generic;
    - estatus_node->task_work.func = NULL;
    estatus = GHES_ESTATUS_FROM_NODE(estatus_node);

    if (__ghes_read_estatus(estatus, buf_paddr, fixmap_idx, len)) {
    diff --git a/include/acpi/ghes.h b/include/acpi/ghes.h
    index 3c8bba9f1114..e5e0c308d27f 100644
    --- a/include/acpi/ghes.h
    +++ b/include/acpi/ghes.h
    @@ -35,9 +35,6 @@ struct ghes_estatus_node {
    struct llist_node llnode;
    struct acpi_hest_generic *generic;
    struct ghes *ghes;
    -
    - int task_work_cpu;
    - struct callback_head task_work;
    };

    struct ghes_estatus_cache {
    diff --git a/mm/memory-failure.c b/mm/memory-failure.c
    index fae9baf3be16..6ea8c325acb3 100644
    --- a/mm/memory-failure.c
    +++ b/mm/memory-failure.c
    @@ -2355,19 +2355,6 @@ static void memory_failure_work_func(struct work_struct *work)
    }
    }

    -/*
    - * Process memory_failure work queued on the specified CPU.
    - * Used to avoid return-to-userspace racing with the memory_failure workqueue.
    - */
    -void memory_failure_queue_kick(int cpu)
    -{
    - struct memory_failure_cpu *mf_cpu;
    -
    - mf_cpu = &per_cpu(memory_failure_cpu, cpu);
    - cancel_work_sync(&mf_cpu->work);
    - memory_failure_work_func(&mf_cpu->work);
    -}
    -
    static int __init memory_failure_init(void)
    {
    struct memory_failure_cpu *mf_cpu;
    --
    2.20.1.12.g72788fdb
    \
     
     \ /
      Last update: 2023-04-11 12:49    [W:4.116 / U:0.072 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site