@@ -237,13 +237,14 @@ ENDPROC(copy_user_enhanced_fast_string)
* Note: Cached memory copy is used when destination or size is not
* naturally aligned. That is:
* - Require 8-byte alignment when size is 8 bytes or larger.
+ * - Require 4-byte alignment when size is 4 bytes.
*/
ENTRY(__copy_user_nocache)
ASM_STAC
- /* If size is less than 8 bytes, goto byte copy */
+ /* If size is less than 8 bytes, goto 4-byte copy */
cmpl $8,%edx
- jb .Lcun_1b_cache_copy_entry
+ jb .Lcun_4b_nocache_copy_entry
/* If destination is not 8-byte aligned, "cache" copy to align it */
ALIGN_DESTINATION
@@ -282,7 +283,7 @@ ENTRY(__copy_user_nocache)
movl %edx,%ecx
andl $7,%edx
shrl $3,%ecx
- jz .Lcun_1b_cache_copy_entry /* jump if count is 0 */
+ jz .Lcun_4b_nocache_copy_entry /* jump if count is 0 */
/* Perform 8-byte nocache loop-copy */
.Lcun_8b_nocache_copy_loop:
@@ -294,11 +295,33 @@ ENTRY(__copy_user_nocache)
jnz .Lcun_8b_nocache_copy_loop
/* If no byte left, we're done */
-.Lcun_1b_cache_copy_entry:
+.Lcun_4b_nocache_copy_entry:
+ andl %edx,%edx
+ jz .Lcun_finish_copy
+
+ /* If destination is not 4-byte aligned, goto byte copy */
+ movl %edi,%ecx
+ andl $3,%ecx
+ jnz .Lcun_1b_cache_copy_entry
+
+ /* Set 4-byte copy count (1 or 0) and remainder */
+ movl %edx,%ecx
+ andl $3,%edx
+ shrl $2,%ecx
+ jz .Lcun_1b_cache_copy_entry /* jump if count is 0 */
+
+ /* Perform 4-byte nocache copy */
+30: movl (%rsi),%r8d
+31: movnti %r8d,(%rdi)
+ leaq 4(%rsi),%rsi
+ leaq 4(%rdi),%rdi
+
+ /* If no byte left, we're done */
andl %edx,%edx
jz .Lcun_finish_copy
/* Perform byte "cache" loop-copy for the remainder */
+.Lcun_1b_cache_copy_entry:
movl %edx,%ecx
.Lcun_1b_cache_copy_loop:
40: movb (%rsi),%al
@@ -323,6 +346,9 @@ ENTRY(__copy_user_nocache)
.Lcun_fixup_8b_copy:
lea (%rdx,%rcx,8),%rdx
jmp .Lcun_fixup_handle_tail
+.Lcun_fixup_4b_copy:
+ lea (%rdx,%rcx,4),%rdx
+ jmp .Lcun_fixup_handle_tail
.Lcun_fixup_1b_copy:
movl %ecx,%edx
.Lcun_fixup_handle_tail:
@@ -348,6 +374,8 @@ ENTRY(__copy_user_nocache)
_ASM_EXTABLE(16b,.Lcun_fixup_4x8b_copy)
_ASM_EXTABLE(20b,.Lcun_fixup_8b_copy)
_ASM_EXTABLE(21b,.Lcun_fixup_8b_copy)
+ _ASM_EXTABLE(30b,.Lcun_fixup_4b_copy)
+ _ASM_EXTABLE(31b,.Lcun_fixup_4b_copy)
_ASM_EXTABLE(40b,.Lcun_fixup_1b_copy)
_ASM_EXTABLE(41b,.Lcun_fixup_1b_copy)
ENDPROC(__copy_user_nocache)
Data corruption issues were observed in tests which initiated a system crash/reset while accessing BTT devices. This problem is reproducible. The BTT driver calls pmem_rw_bytes() to update data in pmem devices. This interface calls __copy_user_nocache(), which uses non-temporal stores so that the stores to pmem are persistent. __copy_user_nocache() uses non-temporal stores when a request size is 8 bytes or larger (and is aligned by 8 bytes). The BTT driver updates the BTT map table, which entry size is 4 bytes. Therefore, updates to the map table entries remain cached, and are not written to pmem after a crash. Change __copy_user_nocache() to use non-temporal store when a request size is 4 bytes. The change extends the current byte-copy path for a less-than-8-bytes request, and does not add any overhead to the regular path. Reported-and-tested-by: Micah Parrish <micah.parrish@hpe.com> Reported-and-tested-by: Brian Boylston <brian.boylston@hpe.com> Signed-off-by: Toshi Kani <toshi.kani@hpe.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Borislav Petkov <bp@suse.de> Cc: Dan Williams <dan.j.williams@intel.com> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Vishal Verma <vishal.l.verma@intel.com> --- arch/x86/lib/copy_user_64.S | 36 ++++++++++++++++++++++++++++++++---- 1 file changed, 32 insertions(+), 4 deletions(-)