mm: make __get_user_pages return -EHWPOISON for HWPOISON page optionally

Make __get_user_pages return -EHWPOISON for HWPOISON page only if
FOLL_HWPOISON is specified.  With this patch, the interested callers
can distinguish HWPOISON pages from general FAULT pages, while other
callers will still get -EFAULT for all these pages, so the user space
interface need not to be changed.

This feature is needed by KVM, where UCR MCE should be relayed to
guest for HWPOISON page, while instruction emulation and MMIO will be
tried for general FAULT page.

The idea comes from Andrew Morton.

Signed-off-by: Huang Ying <ying.huang@intel.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Avi Kivity <avi@redhat.com>

7 files changed, 21 insertions, 3 deletions

diff --git a/arch/alpha/include/asm/errno.h b/arch/alpha/include/asm/errno.h
index 98099bda9370..e5f29ca28180 100644
--- a/arch/alpha/include/asm/errno.h
+++ b/arch/alpha/include/asm/errno.h
@@ -122,4 +122,6 @@
 
 #define ERFKILL         138     /* Operation not possible due to RF-kill */
 
+#define EHWPOISON       139     /* Memory page has hardware error */
+
 #endif
diff --git a/arch/mips/include/asm/errno.h b/arch/mips/include/asm/errno.h
index a0efc73819e4..6dcd3583ed04 100644
--- a/arch/mips/include/asm/errno.h
+++ b/arch/mips/include/asm/errno.h
@@ -121,6 +121,8 @@
 
 #define ERFKILL         167     /* Operation not possible due to RF-kill */
 
+#define EHWPOISON       168     /* Memory page has hardware error */
+
 #define EDQUOT          1133    /* Quota exceeded */
 
 #ifdef __KERNEL__
diff --git a/arch/parisc/include/asm/errno.h b/arch/parisc/include/asm/errno.h
index 9992abdd782d..135ad6047e51 100644
--- a/arch/parisc/include/asm/errno.h
+++ b/arch/parisc/include/asm/errno.h
@@ -122,4 +122,6 @@
 
 #define ERFKILL         256     /* Operation not possible due to RF-kill */
 
+#define EHWPOISON       257     /* Memory page has hardware error */
+
 #endif
diff --git a/arch/sparc/include/asm/errno.h b/arch/sparc/include/asm/errno.h
index 4e2bc490d714..c351aba997b7 100644
--- a/arch/sparc/include/asm/errno.h
+++ b/arch/sparc/include/asm/errno.h
@@ -112,4 +112,6 @@
 
 #define ERFKILL         134     /* Operation not possible due to RF-kill */
 
+#define EHWPOISON       135     /* Memory page has hardware error */
+
 #endif
diff --git a/include/asm-generic/errno.h b/include/asm-generic/errno.h
index 28cc03bf19e6..a1331ce50445 100644
--- a/include/asm-generic/errno.h
+++ b/include/asm-generic/errno.h
@@ -108,4 +108,6 @@
 
 #define ERFKILL         132     /* Operation not possible due to RF-kill */
 
+#define EHWPOISON       133     /* Memory page has hardware error */
+
 #endif
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 46150c66318e..a77c82c56e05 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1532,6 +1532,7 @@ struct page *follow_page(struct vm_area_struct *, unsigned long address,
 #define FOLL_FORCE      0x10    /* get_user_pages read/write w/o permission */
 #define FOLL_MLOCK      0x40    /* mark page as mlocked */
 #define FOLL_SPLIT      0x80    /* don't return transhuge pages, split them */
+#define FOLL_HWPOISON   0x100   /* check page is hwpoisoned */
 
 typedef int (*pte_fn_t)(pte_t *pte, pgtable_t token, unsigned long addr,
                         void *data);
diff --git a/mm/memory.c b/mm/memory.c
index 806a37ec71bd..346ee7e041fd 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1576,9 +1576,16 @@ int __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
                                 if (ret & VM_FAULT_ERROR) {
                                         if (ret & VM_FAULT_OOM)
                                                 return i ? i : -ENOMEM;
-                                        if (ret &
-                                            (VM_FAULT_HWPOISON|VM_FAULT_HWPOISON_LARGE|
-                                             VM_FAULT_SIGBUS))
+                                        if (ret & (VM_FAULT_HWPOISON |
+                                                   VM_FAULT_HWPOISON_LARGE)) {
+                                                if (i)
+                                                        return i;
+                                                else if (gup_flags & FOLL_HWPOISON)
+                                                        return -EHWPOISON;
+                                                else
+                                                        return -EFAULT;
+                                        }
+                                        if (ret & VM_FAULT_SIGBUS)
                                                 return i ? i : -EFAULT;
                                         BUG();
                                 }