+ mm-hwpoison-introduce-copy_mc_highpage.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/hwpoison: introduce copy_mc_highpage
has been added to the -mm mm-unstable branch.  Its filename is
     mm-hwpoison-introduce-copy_mc_highpage.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-hwpoison-introduce-copy_mc_highpage.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Jiaqi Yan <jiaqiyan@google.com>
Subject: mm/hwpoison: introduce copy_mc_highpage
Date: Sat, 4 Mar 2023 22:51:11 -0800

Similar to how copy_mc_user_highpage is implemented for copy_user_highpage
on #MC supported architecture, introduce the #MC handled version of
copy_highpage.

This helper has immediate usage when khugepaged wants to copy file-backed
memory pages and tolerate #MC.

Link: https://lkml.kernel.org/r/20230305065112.1932255-3-jiaqiyan@google.com
Signed-off-by: Jiaqi Yan <jiaqiyan@google.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: "Kirill A . Shutemov" <kirill@shutemov.name>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Naoya Horiguchi <naoya.horiguchi@nec.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Tong Tiangen <tongtiangen@huawei.com>
Cc: Tony Luck <tony.luck@intel.com>
Cc: Yang Shi <shy828301@gmail.com>
Cc: David Stevens <stevensd@chromium.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---


--- a/include/linux/highmem.h~mm-hwpoison-introduce-copy_mc_highpage
+++ a/include/linux/highmem.h
@@ -315,7 +315,29 @@ static inline void copy_user_highpage(st
 
 #endif
 
+#ifndef __HAVE_ARCH_COPY_HIGHPAGE
+
+static inline void copy_highpage(struct page *to, struct page *from)
+{
+	char *vfrom, *vto;
+
+	vfrom = kmap_local_page(from);
+	vto = kmap_local_page(to);
+	copy_page(vto, vfrom);
+	kmsan_copy_page_meta(to, from);
+	kunmap_local(vto);
+	kunmap_local(vfrom);
+}
+
+#endif
+
 #ifdef copy_mc_to_kernel
+/*
+ * If architecture supports machine check exception handling, define the
+ * #MC versions of copy_user_highpage and copy_highpage. They copy a memory
+ * page with #MC in source page (@from) handled, and return the number
+ * of bytes not copied if there was a #MC, otherwise 0 for success.
+ */
 static inline int copy_mc_user_highpage(struct page *to, struct page *from,
 					unsigned long vaddr, struct vm_area_struct *vma)
 {
@@ -332,29 +354,35 @@ static inline int copy_mc_user_highpage(
 
 	return ret;
 }
-#else
-static inline int copy_mc_user_highpage(struct page *to, struct page *from,
-					unsigned long vaddr, struct vm_area_struct *vma)
-{
-	copy_user_highpage(to, from, vaddr, vma);
-	return 0;
-}
-#endif
-
-#ifndef __HAVE_ARCH_COPY_HIGHPAGE
 
-static inline void copy_highpage(struct page *to, struct page *from)
+static inline int copy_mc_highpage(struct page *to, struct page *from)
 {
+	unsigned long ret;
 	char *vfrom, *vto;
 
 	vfrom = kmap_local_page(from);
 	vto = kmap_local_page(to);
-	copy_page(vto, vfrom);
-	kmsan_copy_page_meta(to, from);
+	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
+	if (!ret)
+		kmsan_copy_page_meta(to, from);
 	kunmap_local(vto);
 	kunmap_local(vfrom);
+
+	return ret;
+}
+#else
+static inline int copy_mc_user_highpage(struct page *to, struct page *from,
+					unsigned long vaddr, struct vm_area_struct *vma)
+{
+	copy_user_highpage(to, from, vaddr, vma);
+	return 0;
 }
 
+static inline int copy_mc_highpage(struct page *to, struct page *from)
+{
+	copy_highpage(to, from);
+	return 0;
+}
 #endif
 
 static inline void memcpy_page(struct page *dst_page, size_t dst_off,
_

Patches currently in -mm which might be from jiaqiyan@google.com are

mm-khugepaged-recover-from-poisoned-anonymous-memory.patch
mm-hwpoison-introduce-copy_mc_highpage.patch
mm-khugepaged-recover-from-poisoned-file-backed-memory.patch