diff --git v5.12-rc8/arch/x86/kernel/cpu/mce/core.c v5.12-rc8_patched/arch/x86/kernel/cpu/mce/core.c
index 7962355436da..3ce23445a48c 100644
--- v5.12-rc8/arch/x86/kernel/cpu/mce/core.c
+++ v5.12-rc8_patched/arch/x86/kernel/cpu/mce/core.c
@@ -1257,19 +1257,28 @@ static void kill_me_maybe(struct callback_head *cb)
 {
 	struct task_struct *p = container_of(cb, struct task_struct, mce_kill_me);
 	int flags = MF_ACTION_REQUIRED;
+	int ret;
 
 	pr_err("Uncorrected hardware memory error in user-access at %llx", p->mce_addr);
 
 	if (!p->mce_ripv)
 		flags |= MF_MUST_KILL;
 
-	if (!memory_failure(p->mce_addr >> PAGE_SHIFT, flags) &&
-	    !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) {
+	ret = memory_failure(p->mce_addr >> PAGE_SHIFT, flags);
+	if (!ret && !(p->mce_kflags & MCE_IN_KERNEL_COPYIN)) {
 		set_mce_nospec(p->mce_addr >> PAGE_SHIFT, p->mce_whole_page);
 		sync_core();
 		return;
 	}
 
+	/*
+	 * -EHWPOISON from memory_failure() means that it already sent SIGBUS
+	 * to the current process with the proper error info, so no need to
+	 * send it here again.
+	 */
+	if (ret == -EHWPOISON)
+		return;
+
 	if (p->mce_vaddr != (void __user *)-1l) {
 		force_sig_mceerr(BUS_MCEERR_AR, p->mce_vaddr, PAGE_SHIFT);
 	} else {
diff --git v5.12-rc8/include/linux/swapops.h v5.12-rc8_patched/include/linux/swapops.h
index d9b7c9132c2f..98ea67fcf360 100644
--- v5.12-rc8/include/linux/swapops.h
+++ v5.12-rc8_patched/include/linux/swapops.h
@@ -323,6 +323,11 @@ static inline int is_hwpoison_entry(swp_entry_t entry)
 	return swp_type(entry) == SWP_HWPOISON;
 }
 
+static inline unsigned long hwpoison_entry_to_pfn(swp_entry_t entry)
+{
+	return swp_offset(entry);
+}
+
 static inline void num_poisoned_pages_inc(void)
 {
 	atomic_long_inc(&num_poisoned_pages);
diff --git v5.12-rc8/mm/memory-failure.c v5.12-rc8_patched/mm/memory-failure.c
index 39d0ff0339b9..7cc563e1770a 100644
--- v5.12-rc8/mm/memory-failure.c
+++ v5.12-rc8_patched/mm/memory-failure.c
@@ -56,6 +56,7 @@
 #include <linux/kfifo.h>
 #include <linux/ratelimit.h>
 #include <linux/page-isolation.h>
+#include <linux/pagewalk.h>
 #include "internal.h"
 #include "ras/ras_event.h"
 
@@ -554,6 +555,141 @@ static void collect_procs(struct page *page, struct list_head *tokill,
 		collect_procs_file(page, tokill, force_early);
 }
 
+struct hwp_walk {
+	struct to_kill tk;
+	unsigned long pfn;
+	int flags;
+};
+
+static int set_to_kill(struct to_kill *tk, unsigned long addr, short shift)
+{
+	/* Abort pagewalk when finding multiple mappings to the error page. */
+	if (tk->addr)
+		return 1;
+	tk->addr = addr;
+	tk->size_shift = shift;
+	return 0;
+}
+
+static int check_hwpoisoned_entry(pte_t pte, unsigned long addr, short shift,
+				unsigned long poisoned_pfn, struct to_kill *tk)
+{
+	unsigned long pfn = 0;
+
+	if (pte_present(pte)) {
+		pfn = pte_pfn(pte);
+	} else {
+		swp_entry_t swp = pte_to_swp_entry(pte);
+
+		if (is_hwpoison_entry(swp))
+			pfn = hwpoison_entry_to_pfn(swp);
+	}
+
+	if (!pfn || pfn != poisoned_pfn)
+		return 0;
+
+	return set_to_kill(tk, addr, shift);
+}
+
+static int hwpoison_pte_range(pmd_t *pmdp, unsigned long addr,
+			      unsigned long end, struct mm_walk *walk)
+{
+	struct hwp_walk *hwp = (struct hwp_walk *)walk->private;
+	int ret = 0;
+	pte_t *ptep;
+	spinlock_t *ptl;
+
+	ptl = pmd_trans_huge_lock(pmdp, walk->vma);
+	if (ptl) {
+		pmd_t pmd = *pmdp;
+
+		if (pmd_present(pmd)) {
+			unsigned long pfn = pmd_pfn(pmd);
+
+			if (pfn <= hwp->pfn && hwp->pfn < pfn + HPAGE_PMD_NR) {
+				unsigned long hwpoison_vaddr = addr +
+					((hwp->pfn - pfn) << PAGE_SHIFT);
+
+				ret = set_to_kill(&hwp->tk, hwpoison_vaddr,
+						  PAGE_SHIFT);
+			}
+		}
+		spin_unlock(ptl);
+		goto out;
+	}
+
+	if (pmd_trans_unstable(pmdp))
+		goto out;
+
+	ptep = pte_offset_map_lock(walk->vma->vm_mm, pmdp, addr, &ptl);
+	for (; addr != end; ptep++, addr += PAGE_SIZE) {
+		ret = check_hwpoisoned_entry(*ptep, addr, PAGE_SHIFT,
+					     hwp->pfn, &hwp->tk);
+		if (ret == 1)
+			break;
+	}
+	pte_unmap_unlock(ptep - 1, ptl);
+out:
+	cond_resched();
+	return ret;
+}
+
+#ifdef CONFIG_HUGETLB_PAGE
+static int hwpoison_hugetlb_range(pte_t *ptep, unsigned long hmask,
+			    unsigned long addr, unsigned long end,
+			    struct mm_walk *walk)
+{
+	struct hwp_walk *hwp = (struct hwp_walk *)walk->private;
+	pte_t pte = huge_ptep_get(ptep);
+	struct hstate *h = hstate_vma(walk->vma);
+
+	return check_hwpoisoned_entry(pte, addr, huge_page_shift(h),
+				      hwp->pfn, &hwp->tk);
+}
+#else
+#define hwpoison_hugetlb_range	NULL
+#endif
+
+static struct mm_walk_ops hwp_walk_ops = {
+	.pmd_entry = hwpoison_pte_range,
+	.hugetlb_entry = hwpoison_hugetlb_range,
+};
+
+/*
+ * Sends SIGBUS to the current process with the error info.
+ *
+ * This function is intended to handle "Action Required" MCEs on already
+ * hardware poisoned pages. They could happen, for example, when
+ * memory_failure() failed to unmap the error page at the first call, or
+ * when multiple local machine checks happened on different CPUs.
+ *
+ * MCE handler currently has no easy access to the error virtual address,
+ * so this function walks page table to find it. One challenge on this is
+ * to reliably get the proper virual address of the error to report to
+ * applications via SIGBUS. A process could map a page multiple times to
+ * different virtual addresses, then we now have no way to tell which virtual
+ * address was accessed when the Action Required MCE was generated.
+ * So in such a corner case, we now give up and fall back to sending SIGBUS
+ * with no error info.
+ */
+static int kill_accessing_process(struct task_struct *p, unsigned long pfn,
+				  int flags)
+{
+	int ret;
+	struct hwp_walk priv = {
+		.pfn = pfn,
+	};
+	priv.tk.tsk = p;
+
+	mmap_read_lock(p->mm);
+	ret = walk_page_range(p->mm, 0, TASK_SIZE_MAX, &hwp_walk_ops,
+			      (void *)&priv);
+	if (!ret && priv.tk.addr)
+		kill_proc(&priv.tk, pfn, flags);
+	mmap_read_unlock(p->mm);
+	return ret ? -EFAULT : -EHWPOISON;
+}
+
 static const char *action_name[] = {
 	[MF_IGNORED] = "Ignored",
 	[MF_FAILED] = "Failed",
@@ -1228,7 +1364,10 @@ static int memory_failure_hugetlb(unsigned long pfn, int flags)
 	if (TestSetPageHWPoison(head)) {
 		pr_err("Memory failure: %#lx: already hardware poisoned\n",
 		       pfn);
-		return -EHWPOISON;
+		res = -EHWPOISON;
+		if (flags & MF_ACTION_REQUIRED)
+			res = kill_accessing_process(current, page_to_pfn(head), flags);
+		return res;
 	}
 
 	num_poisoned_pages_inc();
@@ -1438,6 +1577,8 @@ int memory_failure(unsigned long pfn, int flags)
 		pr_err("Memory failure: %#lx: already hardware poisoned\n",
 			pfn);
 		res = -EHWPOISON;
+		if (flags & MF_ACTION_REQUIRED)
+			res = kill_accessing_process(current, pfn, flags);
 		goto unlock_mutex;
 	}
 
