ACPI: APEI: handle synchronous exceptions in task work

The memory uncorrected error could be signaled by asynchronous interrupt
(specifically, SPI in arm64 platform), e.g. when an error is detected by
a background scrubber, or signaled by synchronous exception
(specifically, data abort exception in arm64 platform), e.g. when a CPU
tries to access a poisoned cache line. Currently, both synchronous and
asynchronous errors use memory_failure_queue() to schedule
memory_failure() to exectute in a kworker context.

As a result, when a user-space process is accessing a poisoned data, a
data abort is taken and the memory_failure() is executed in the kworker
context, which:

  - will send wrong si_code by SIGBUS signal in early_kill mode, and
  - can not kill the user-space in some cases resulting a synchronous
    error infinite loop

Issue 1: send wrong si_code in early_kill mode

Since commit a70297d22132 ("ACPI: APEI: set memory failure flags as
MF_ACTION_REQUIRED on synchronous events")', the flag MF_ACTION_REQUIRED
could be used to determine whether a synchronous exception occurs on
ARM64 platform.  When a synchronous exception is detected, the kernel is
expected to terminate the current process which has accessed a poisoned
page. This is done by sending a SIGBUS signal with error code
BUS_MCEERR_AR, indicating an action-required machine check error on
read.

However, when kill_proc() is called to terminate the processes who has
the poisoned page mapped, it sends the incorrect SIGBUS error code
BUS_MCEERR_AO because the context in which it operates is not the one
where the error was triggered.

To reproduce this problem:

  #sysctl -w vm.memory_failure_early_kill=1
  vm.memory_failure_early_kill = 1

  # STEP2: inject an UCE error and consume it to trigger a synchronous error
  #einj_mem_uc single
  0: single   vaddr = 0xffffb0d75400 paddr = 4092d55b400
  injecting ...
  triggering ...
  signal 7 code 5 addr 0xffffb0d75000
  page not present
  Test passed

The si_code (code 5) from einj_mem_uc indicates that it is BUS_MCEERR_AO
error and it is not factually correct.

After this change:

  # STEP1: enable early kill mode
  #sysctl -w vm.memory_failure_early_kill=1
  vm.memory_failure_early_kill = 1
  # STEP2: inject an UCE error and consume it to trigger a synchronous error
  #einj_mem_uc single
  0: single   vaddr = 0xffffb0d75400 paddr = 4092d55b400
  injecting ...
  triggering ...
  signal 7 code 4 addr 0xffffb0d75000
  page not present
  Test passed

The si_code (code 4) from einj_mem_uc indicates that it is a BUS_MCEERR_AR
error as expected.

Issue 2: a synchronous error infinite loop

If a user-space process, e.g. devmem, accesses a poisoned page for which
the HWPoison flag is set, kill_accessing_process() is called to send
SIGBUS to current processs with error info. Since the memory_failure()
is executed in the kworker context, it will just do nothing but return
EFAULT. So, devmem will access the posioned page and trigger an
exception again, resulting in a synchronous error infinite loop. Such
exception loop may cause platform firmware to exceed some threshold and
reboot when Linux could have recovered from this error.

To reproduce this problem:

  # STEP 1: inject an UCE error, and kernel will set HWPosion flag for related page
  #einj_mem_uc single
  0: single   vaddr = 0xffffb0d75400 paddr = 4092d55b400
  injecting ...
  triggering ...
  signal 7 code 4 addr 0xffffb0d75000
  page not present
  Test passed

  # STEP 2: access the same page and it will trigger a synchronous error infinite loop
  devmem 0x4092d55b400

To fix above two issues, queue memory_failure() as a task_work so that
it runs in the context of the process that is actually consuming the
poisoned data.

Signed-off-by: Shuai Xue <xueshuai@linux.alibaba.com>
Tested-by: Ma Wupeng <mawupeng1@huawei.com>
Reviewed-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Reviewed-by: Xiaofei Tan <tanxiaofei@huawei.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Jane Chu <jane.chu@oracle.com>
Reviewed-by: Yazen Ghannam <yazen.ghannam@amd.com>
Reviewed-by: Hanjun Guo <guohanjun@huawei.com>
Link: https://patch.msgid.link/20250714114212.31660-3-xueshuai@linux.alibaba.com
[ rjw: Changelog edits ]
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
index bda33a0f0a01316d639493ef08912ca41eb23b8e..a0d54993edb3b6fbd265664ca5d11507767f815c 100644 (file)
--- a/drivers/acpi/apei/ghes.c
+++ b/drivers/acpi/apei/ghes.c
@@ -464,28 +464,41 @@ static void ghes_clear_estatus(struct ghes *ghes,
                ghes_ack_error(ghes->generic_v2);
 }
 
-/*
- * 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 ghes_task_work - for synchronous RAS event
+ *
+ * @twork:                callback_head for task work
+ * @pfn:                  page frame number of corrupted page
+ * @flags:                work control flags
+ *
+ * Structure to pass task work to be handled before
+ * returning to user-space via task_work_add().
  */
-static void ghes_kick_task_work(struct callback_head *head)
+struct ghes_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;
+       struct ghes_task_work *twcb = container_of(twork, struct ghes_task_work, twork);
+       int ret;
 
-       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);
+       gen_pool_free(ghes_estatus_pool, (unsigned long)twcb, sizeof(*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 || ret == -EHWPOISON || ret == -EOPNOTSUPP)
+               return;
+
+       pr_err("%#llx: Sending SIGBUS to %s:%d due to hardware memory corruption\n",
+                       twcb->pfn, current->comm, task_pid_nr(current));
+       force_sig(SIGBUS);
 }
 
 static bool ghes_do_memory_failure(u64 physical_addr, int flags)
 {
+       struct ghes_task_work *twcb;
        unsigned long pfn;
 
        if (!IS_ENABLED(CONFIG_ACPI_APEI_MEMORY_FAILURE))
@@ -499,6 +512,18 @@ static bool ghes_do_memory_failure(u64 physical_addr, int flags)
                return false;
        }
 
+       if (flags == MF_ACTION_REQUIRED && current->mm) {
+               twcb = (void *)gen_pool_alloc(ghes_estatus_pool, sizeof(*twcb));
+               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;
 }
@@ -842,7 +867,7 @@ int cxl_cper_kfifo_get(struct cxl_cper_work_data *wd)
 }
 EXPORT_SYMBOL_NS_GPL(cxl_cper_kfifo_get, "CXL");
 
-static bool ghes_do_proc(struct ghes *ghes,
+static void ghes_do_proc(struct ghes *ghes,
                         const struct acpi_hest_generic_status *estatus)
 {
        int sev, sec_sev;
@@ -912,8 +937,6 @@ static bool ghes_do_proc(struct ghes *ghes,
                        current->comm, task_pid_nr(current));
                force_sig(SIGBUS);
        }
-
-       return queued;
 }
 
 static void __ghes_print_estatus(const char *pfx,
@@ -1219,9 +1242,7 @@ 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;
        u32 len, node_len;
-       int ret;
 
        llnode = llist_del_all(&ghes_estatus_llist);
        /*
@@ -1236,25 +1257,16 @@ static void ghes_proc_in_irq(struct irq_work *irq_work)
                estatus = GHES_ESTATUS_FROM_NODE(estatus_node);
                len = cper_estatus_len(estatus);
                node_len = GHES_ESTATUS_NODE_LEN(len);
-               task_work_pending = ghes_do_proc(estatus_node->ghes, estatus);
+
+               ghes_do_proc(estatus_node->ghes, estatus);
+
                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;
        }
@@ -1315,7 +1327,6 @@ 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 be1dd4c1a917447c1d20d59ef0de7df423758e1d..ebd21b05fe6ed1ffb64e64136b91cbfa62b8ee1e 100644 (file)
--- 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/include/linux/mm.h b/include/linux/mm.h
index 0ef2ba0c667af03b121dd7311fa392042c29c56c..02dffff2508bc4462a68f5a547dc45c2023b8b73 100644 (file)
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -3896,7 +3896,6 @@ enum mf_flags {
 int mf_dax_kill_procs(struct address_space *mapping, pgoff_t index,
                      unsigned long count, int mf_flags);
 extern int memory_failure(unsigned long pfn, int flags);
-extern void memory_failure_queue_kick(int cpu);
 extern int unpoison_memory(unsigned long pfn);
 extern atomic_long_t num_poisoned_pages __read_mostly;
 extern int soft_offline_page(unsigned long pfn, int flags);

diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index b91a33fb6c694fb830e73661ec0dfb55d8eea62f..5278132a2b6d91969a3702c750b1cc31ea9ffed6 100644 (file)
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -2503,19 +2503,6 @@ 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;