RE: [PATCH v7 1/2] mm/khugepaged: recover from poisoned anonymous memory

["Luck, Tony" <tony.luck@intel.com>]

+/*
+ * Machine check exception handled version of copy_highpage.
+ * Return true if copying page content failed; otherwise false.
+ * Note handling #MC requires arch opt-in.
+ */
+static inline bool copy_highpage_mc(struct page *to, struct page *from)
+{
+	char *vfrom, *vto;
+	unsigned long ret;
+
+	vfrom = kmap_local_page(from);
+	vto = kmap_local_page(to);
+	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
+	kunmap_local(vto);
+	kunmap_local(vfrom);
+
+	return ret > 0;
+}

Andrew Morton took my patches to recover from copy-on-write faults
into the -mm tree. They are now sitting in linux-next (hopefully) ready
for the next merge window.

I had copied this function from an earlier version of your patch, but
there was a suggestion that copy_mc_user_highpage() would be a
more consistent name with other copy code that can handle machine
checks. There was also an upstream change to copy_highpage()
that needed to be reflected here.

Net result, this version is already in flight:

static inline int copy_mc_user_highpage(struct page *to, struct page *from,
					unsigned long vaddr, struct vm_area_struct *vma)
{
	unsigned long ret;
	char *vfrom, *vto;

	vfrom = kmap_local_page(from);
	vto = kmap_local_page(to);
	ret = copy_mc_to_kernel(vto, vfrom, PAGE_SIZE);
	if (!ret)
		kmsan_unpoison_memory(page_address(to), PAGE_SIZE);
	kunmap_local(vto);
	kunmap_local(vfrom);

	return ret;
}

-Tony