[PATCH -next v5 2/3] x86/mce: set MCE_IN_KERNEL_COPYIN for DEFAULT_MCE_SAFE exception

[Tong Tiangen <tongtiangen@huawei.com>]

From: Kefeng Wang <wangkefeng.wang@huawei.com>

Currently, some kernel memory copy scenarios[1][2][3] which use
copy_mc_{user_}highpage() to safely abort copy and report 'bytes not copied'
when accessing the poisoned source page, a recoverable synchronous exception
generated in the processing and the fixup type EX_TYPE_DEFAULT_MCE_SAFE is
used to distinguish from other exceptions, and an asynchronous
memory_failure_queue() is called to handle memory failure of the source page
, but scheduling someone else to handle it at some future point is
unpredictable and risky.

The better way is immediately deal with it during current context,
fortunately, there is already a framework to synchronously call
memory_failure(), see kill_me_never() in do_machine_check(), a task work is
triggered once MCE_IN_KERNEL_COPYIN is set, in order to fix above issue,
setting MCE_IN_KERNEL_COPYIN for EX_TYPE_DEFAULT_MCE_SAFE case too.

[1] commit d302c2398ba2 ("mm, hwpoison: when copy-on-write hits poison, take page offline")
[2] commit 1cb9dc4b475c ("mm: hwpoison: support recovery from HugePage copy-on-write faults")
[3] commit 6b970599e807 ("mm: hwpoison: support recovery from ksm_might_need_to_copy()")

Reviewed-by: Naoya Horiguchi <naoya.horiguchi@nec.com>
Reviewed-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Signed-off-by: Tong Tiangen <tongtiangen@huawei.com>
---
 arch/x86/kernel/cpu/mce/severity.c |  4 ++--
 mm/ksm.c                           |  1 -
 mm/memory.c                        | 13 ++++---------
 3 files changed, 6 insertions(+), 12 deletions(-)

diff --git a/arch/x86/kernel/cpu/mce/severity.c b/arch/x86/kernel/cpu/mce/severity.c
index bca780fa5e57..b2cce1b6c96d 100644
--- a/arch/x86/kernel/cpu/mce/severity.c
+++ b/arch/x86/kernel/cpu/mce/severity.c
@@ -292,11 +292,11 @@ static noinstr int error_context(struct mce *m, struct pt_regs *regs)
 	case EX_TYPE_UACCESS:
 		if (!copy_user)
 			return IN_KERNEL;
+		fallthrough;
+	case EX_TYPE_DEFAULT_MCE_SAFE:
 		m->kflags |= MCE_IN_KERNEL_COPYIN;
 		fallthrough;
-
 	case EX_TYPE_FAULT_MCE_SAFE:
-	case EX_TYPE_DEFAULT_MCE_SAFE:
 		m->kflags |= MCE_IN_KERNEL_RECOV;
 		return IN_KERNEL_RECOV;
 
diff --git a/mm/ksm.c b/mm/ksm.c
index 8c001819cf10..ba9d324ea1c6 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -3084,7 +3084,6 @@ struct folio *ksm_might_need_to_copy(struct folio *folio,
 		if (copy_mc_user_highpage(folio_page(new_folio, 0), page,
 								addr, vma)) {
 			folio_put(new_folio);
-			memory_failure_queue(folio_pfn(folio), 0);
 			return ERR_PTR(-EHWPOISON);
 		}
 		folio_set_dirty(new_folio);
diff --git a/mm/memory.c b/mm/memory.c
index 8d14ba440929..ee06a8f766ab 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -2846,10 +2846,8 @@ static inline int __wp_page_copy_user(struct page *dst, struct page *src,
 	unsigned long addr = vmf->address;
 
 	if (likely(src)) {
-		if (copy_mc_user_highpage(dst, src, addr, vma)) {
-			memory_failure_queue(page_to_pfn(src), 0);
+		if (copy_mc_user_highpage(dst, src, addr, vma))
 			return -EHWPOISON;
-		}
 		return 0;
 	}
 
@@ -6179,10 +6177,8 @@ static int copy_user_gigantic_page(struct folio *dst, struct folio *src,
 
 		cond_resched();
 		if (copy_mc_user_highpage(dst_page, src_page,
-					  addr + i*PAGE_SIZE, vma)) {
-			memory_failure_queue(page_to_pfn(src_page), 0);
+					  addr + i*PAGE_SIZE, vma))
 			return -EHWPOISON;
-		}
 	}
 	return 0;
 }
@@ -6199,10 +6195,9 @@ static int copy_subpage(unsigned long addr, int idx, void *arg)
 	struct page *dst = nth_page(copy_arg->dst, idx);
 	struct page *src = nth_page(copy_arg->src, idx);
 
-	if (copy_mc_user_highpage(dst, src, addr, copy_arg->vma)) {
-		memory_failure_queue(page_to_pfn(src), 0);
+	if (copy_mc_user_highpage(dst, src, addr, copy_arg->vma))
 		return -EHWPOISON;
-	}
+
 	return 0;
 }
 
-- 
2.25.1