From 1179f170b6f0af7bb0b3b7628136eaac450ddf31 Mon Sep 17 00:00:00 2001 From: Sven Schnelle Date: Fri, 20 Nov 2020 14:17:52 +0100 Subject: s390: fix fpu restore in entry.S We need to disable interrupts in load_fpu_regs(). Otherwise an interrupt might come in after the registers are loaded, but before CIF_FPU is cleared in load_fpu_regs(). When the interrupt returns, CIF_FPU will be cleared and the registers will never be restored. The entry.S code usually saves the interrupt state in __SF_EMPTY on the stack when disabling/restoring interrupts. sie64a however saves the pointer to the sie control block in __SF_SIE_CONTROL, which references the same location. This is non-obvious to the reader. To avoid thrashing the sie control block pointer in load_fpu_regs(), move the __SIE_* offsets eight bytes after __SF_EMPTY on the stack. Cc: # 5.8 Fixes: 0b0ed657fe00 ("s390: remove critical section cleanup from entry.S") Reported-by: Pierre Morel Signed-off-by: Sven Schnelle Acked-by: Christian Borntraeger Reviewed-by: Heiko Carstens Signed-off-by: Heiko Carstens --- arch/s390/kernel/entry.S | 2 ++ 1 file changed, 2 insertions(+) (limited to 'arch/s390/kernel/entry.S') diff --git a/arch/s390/kernel/entry.S b/arch/s390/kernel/entry.S index 5346545b9860..26bb0603c5a1 100644 --- a/arch/s390/kernel/entry.S +++ b/arch/s390/kernel/entry.S @@ -1068,6 +1068,7 @@ EXPORT_SYMBOL(save_fpu_regs) * %r4 */ load_fpu_regs: + stnsm __SF_EMPTY(%r15),0xfc lg %r4,__LC_CURRENT aghi %r4,__TASK_thread TSTMSK __LC_CPU_FLAGS,_CIF_FPU @@ -1099,6 +1100,7 @@ load_fpu_regs: .Lload_fpu_regs_done: ni __LC_CPU_FLAGS+7,255-_CIF_FPU .Lload_fpu_regs_exit: + ssm __SF_EMPTY(%r15) BR_EX %r14 .Lload_fpu_regs_end: ENDPROC(load_fpu_regs) -- cgit v1.2.3-59-g8ed1b