+/* + * 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