Revert "powerpc/64: Avoid restore_math call if possible in syscall exit"
This reverts commit bc4f65e4cf9d6cc43e0e9ba0b8648cf9201cd55f.
As reported by Andreas, this commit is causing unrecoverable SLB misses in the
system call exit path:
Unrecoverable exception 4100 at c00000000000a1ec
Oops: Unrecoverable exception, sig: 6 [#1]
SMP NR_CPUS=2 PowerMac
...
CPU: 0 PID: 18626 Comm: rm Not tainted 4.13.0-rc3 #1
task: c00000018335e080 task.stack: c000000139e50000
NIP: c00000000000a1ec LR: c00000000000a118 CTR: 0000000000000000
REGS: c000000139e53bb0 TRAP: 4100 Not tainted (4.13.0-rc3)
MSR: 9000000000001030 <SF,HV,ME,IR,DR> CR: 24000044 XER: 20000000 SOFTE: 1
GPR00: 0000000000000000 c000000139e53e30 c000000000abb500 fffffffffffffffe
GPR04: c0000001eb866298 0000000000000000 0000000000000000 c00000018335e080
GPR08: 900000000000d032 0000000000000000 0000000000000002 fffffffffffff001
GPR12: c000000139e50000 c00000000ffff000 00003fffa8c0dca0 00003fffa8c0dc88
GPR16: 0000000010000000 0000000000000001 00003fffa8c0eaa0 0000000000000000
GPR20: 00003fffa8c27528 00003fffa8c27b00 0000000000000000 0000000000000000
GPR24: 00003fffa8c0d918 00003ffff1b3efa0 00003fffa8c26d68 0000000000000000
GPR28: 00003fffa8c249e8 00003fffa8c263d0 00003fffa8c27550 00003ffff1b3ef10
NIP [c00000000000a1ec] system_call_exit+0xc0/0x21c
LR [c00000000000a118] system_call+0x58/0x6c
Call Trace:
[c000000139e53e30] [c00000000000a118] system_call+0x58/0x6c (unreliable)
Instruction dump:
64a51000 7c6300d0 f8a101a0 4bffff9c 3c000000 60000006 780007c6 64000000
60000000 7c004039 4082001c e8ed0170 <88070b78> 88c70b79 7c003214 2c200000
This is caused by us trying to load THREAD_LOAD_FP with MSR_RI=0, and taking an
SLB miss on the thread struct.
Reported-by: Andreas Schwab <schwab@linux-m68k.org>
Diagnosed-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
diff --git a/arch/powerpc/kernel/entry_64.S b/arch/powerpc/kernel/entry_64.S
index 49d8422..e925c1c 100644
--- a/arch/powerpc/kernel/entry_64.S
+++ b/arch/powerpc/kernel/entry_64.S
@@ -223,17 +223,27 @@
andi. r0,r9,(_TIF_SYSCALL_DOTRACE|_TIF_SINGLESTEP|_TIF_USER_WORK_MASK|_TIF_PERSYSCALL_MASK)
bne- .Lsyscall_exit_work
- /* If MSR_FP and MSR_VEC are set in user msr, then no need to restore */
- li r7,MSR_FP
+ andi. r0,r8,MSR_FP
+ beq 2f
#ifdef CONFIG_ALTIVEC
- oris r7,r7,MSR_VEC@h
+ andis. r0,r8,MSR_VEC@h
+ bne 3f
#endif
- and r0,r8,r7
- cmpd r0,r7
- bne .Lsyscall_restore_math
-.Lsyscall_restore_math_cont:
+2: addi r3,r1,STACK_FRAME_OVERHEAD
+#ifdef CONFIG_PPC_BOOK3S
+ li r10,MSR_RI
+ mtmsrd r10,1 /* Restore RI */
+#endif
+ bl restore_math
+#ifdef CONFIG_PPC_BOOK3S
+ li r11,0
+ mtmsrd r11,1
+#endif
+ ld r8,_MSR(r1)
+ ld r3,RESULT(r1)
+ li r11,-MAX_ERRNO
- cmpld r3,r11
+3: cmpld r3,r11
ld r5,_CCR(r1)
bge- .Lsyscall_error
.Lsyscall_error_cont:
@@ -267,40 +277,6 @@
std r5,_CCR(r1)
b .Lsyscall_error_cont
-.Lsyscall_restore_math:
- /*
- * Some initial tests from restore_math to avoid the heavyweight
- * C code entry and MSR manipulations.
- */
- LOAD_REG_IMMEDIATE(r0, MSR_TS_MASK)
- and. r0,r0,r8
- bne 1f
-
- ld r7,PACACURRENT(r13)
- lbz r0,THREAD+THREAD_LOAD_FP(r7)
-#ifdef CONFIG_ALTIVEC
- lbz r6,THREAD+THREAD_LOAD_VEC(r7)
- add r0,r0,r6
-#endif
- cmpdi r0,0
- beq .Lsyscall_restore_math_cont
-
-1: addi r3,r1,STACK_FRAME_OVERHEAD
-#ifdef CONFIG_PPC_BOOK3S
- li r10,MSR_RI
- mtmsrd r10,1 /* Restore RI */
-#endif
- bl restore_math
-#ifdef CONFIG_PPC_BOOK3S
- li r11,0
- mtmsrd r11,1
-#endif
- /* Restore volatiles, reload MSR from updated one */
- ld r8,_MSR(r1)
- ld r3,RESULT(r1)
- li r11,-MAX_ERRNO
- b .Lsyscall_restore_math_cont
-
/* Traced system call support */
.Lsyscall_dotrace:
bl save_nvgprs
diff --git a/arch/powerpc/kernel/process.c b/arch/powerpc/kernel/process.c
index 9f3e2c9..ec48096 100644
--- a/arch/powerpc/kernel/process.c
+++ b/arch/powerpc/kernel/process.c
@@ -511,10 +511,6 @@ void restore_math(struct pt_regs *regs)
{
unsigned long msr;
- /*
- * Syscall exit makes a similar initial check before branching
- * to restore_math. Keep them in synch.
- */
if (!msr_tm_active(regs->msr) &&
!current->thread.load_fp && !loadvec(current->thread))
return;