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Commit 6b73044b authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

s390: run user space and KVM guests with modified branch prediction 



Define TIF_ISOLATE_BP and TIF_ISOLATE_BP_GUEST and add the necessary
plumbing in entry.S to be able to run user space and KVM guests with
limited branch prediction.

To switch a user space process to limited branch prediction the
s390_isolate_bp() function has to be call, and to run a vCPU of a KVM
guest associated with the current task with limited branch prediction
call s390_isolate_bp_guest().

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent d768bd89

arch/s390/include/asm/processor.h

+3 −0
Original line number Diff line number Diff line
@@ -378,6 +378,9 @@ extern void memcpy_absolute(void *, void *, size_t); 
	memcpy_absolute(&(dest), &__tmp, sizeof(__tmp));	\

} while (0)



extern int s390_isolate_bp(void);

extern int s390_isolate_bp_guest(void);



#endif /* __ASSEMBLY__ */



#endif /* __ASM_S390_PROCESSOR_H */

arch/s390/include/asm/thread_info.h

+4 −0
Original line number Diff line number Diff line
@@ -58,6 +58,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); 
#define TIF_GUARDED_STORAGE	4	/* load guarded storage control block */

#define TIF_PATCH_PENDING	5	/* pending live patching update */

#define TIF_PGSTE		6	/* New mm's will use 4K page tables */

#define TIF_ISOLATE_BP		8	/* Run process with isolated BP */

#define TIF_ISOLATE_BP_GUEST	9	/* Run KVM guests with isolated BP */



#define TIF_31BIT		16	/* 32bit process */

#define TIF_MEMDIE		17	/* is terminating due to OOM killer */
@@ -78,6 +80,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src); 
#define _TIF_UPROBE		_BITUL(TIF_UPROBE)

#define _TIF_GUARDED_STORAGE	_BITUL(TIF_GUARDED_STORAGE)

#define _TIF_PATCH_PENDING	_BITUL(TIF_PATCH_PENDING)

#define _TIF_ISOLATE_BP		_BITUL(TIF_ISOLATE_BP)

#define _TIF_ISOLATE_BP_GUEST	_BITUL(TIF_ISOLATE_BP_GUEST)



#define _TIF_31BIT		_BITUL(TIF_31BIT)

#define _TIF_SINGLE_STEP	_BITUL(TIF_SINGLE_STEP)

arch/s390/kernel/entry.S

+46 −5
Original line number Diff line number Diff line
@@ -107,6 +107,7 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART) 
	aghi	%r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)

	j	3f

1:	UPDATE_VTIME %r14,%r15,\timer

	BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP

2:	lg	%r15,__LC_ASYNC_STACK	# load async stack

3:	la	%r11,STACK_FRAME_OVERHEAD(%r15)

	.endm
@@ -187,6 +188,40 @@ _PIF_WORK = (_PIF_PER_TRAP | _PIF_SYSCALL_RESTART) 
	.popsection

	.endm



	.macro BPENTER tif_ptr,tif_mask

	.pushsection .altinstr_replacement, "ax"

662:	.word	0xc004, 0x0000, 0x0000	# 6 byte nop

	.word	0xc004, 0x0000, 0x0000	# 6 byte nop

	.popsection

664:	TSTMSK	\tif_ptr,\tif_mask

	jz	. + 8

	.long	0xb2e8d000

	.pushsection .altinstructions, "a"

	.long 664b - .

	.long 662b - .

	.word 82

	.byte 12

	.byte 12

	.popsection

	.endm



	.macro BPEXIT tif_ptr,tif_mask

	TSTMSK	\tif_ptr,\tif_mask

	.pushsection .altinstr_replacement, "ax"

662:	jnz	. + 8

	.long	0xb2e8d000

	.popsection

664:	jz	. + 8

	.long	0xb2e8c000

	.pushsection .altinstructions, "a"

	.long 664b - .

	.long 662b - .

	.word 82

	.byte 8

	.byte 8

	.popsection

	.endm



	.section .kprobes.text, "ax"

.Ldummy:

	/*
@@ -240,9 +275,11 @@ ENTRY(__switch_to) 
 */

ENTRY(sie64a)

	stmg	%r6,%r14,__SF_GPRS(%r15)	# save kernel registers

	lg	%r12,__LC_CURRENT

	stg	%r2,__SF_EMPTY(%r15)		# save control block pointer

	stg	%r3,__SF_EMPTY+8(%r15)		# save guest register save area

	xc	__SF_EMPTY+16(8,%r15),__SF_EMPTY+16(%r15) # reason code = 0

	mvc	__SF_EMPTY+24(8,%r15),__TI_flags(%r12) # copy thread flags

	TSTMSK	__LC_CPU_FLAGS,_CIF_FPU		# load guest fp/vx registers ?

	jno	.Lsie_load_guest_gprs

	brasl	%r14,load_fpu_regs		# load guest fp/vx regs
@@ -259,11 +296,12 @@ ENTRY(sie64a) 
	jnz	.Lsie_skip

	TSTMSK	__LC_CPU_FLAGS,_CIF_FPU

	jo	.Lsie_skip			# exit if fp/vx regs changed

	BPON

	BPEXIT	__SF_EMPTY+24(%r15),(_TIF_ISOLATE_BP|_TIF_ISOLATE_BP_GUEST)

.Lsie_entry:

	sie	0(%r14)

.Lsie_exit:

	BPOFF

	BPENTER	__SF_EMPTY+24(%r15),(_TIF_ISOLATE_BP|_TIF_ISOLATE_BP_GUEST)

.Lsie_skip:

	ni	__SIE_PROG0C+3(%r14),0xfe	# no longer in SIE

	lctlg	%c1,%c1,__LC_USER_ASCE		# load primary asce
@@ -324,6 +362,7 @@ ENTRY(system_call) 
	la	%r11,STACK_FRAME_OVERHEAD(%r15)	# pointer to pt_regs

.Lsysc_vtime:

	UPDATE_VTIME %r8,%r9,__LC_SYNC_ENTER_TIMER

	BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP

	stmg	%r0,%r7,__PT_R0(%r11)

	# clear user controlled register to prevent speculative use

	xgr	%r0,%r0
@@ -362,7 +401,7 @@ ENTRY(system_call) 
	jnz	.Lsysc_work			# check for work

	TSTMSK	__LC_CPU_FLAGS,_CIF_WORK

	jnz	.Lsysc_work

	BPON

	BPEXIT	__TI_flags(%r12),_TIF_ISOLATE_BP

.Lsysc_restore:

	lg	%r14,__LC_VDSO_PER_CPU

	lmg	%r0,%r10,__PT_R0(%r11)
@@ -597,6 +636,7 @@ ENTRY(pgm_check_handler) 
	aghi	%r15,-(STACK_FRAME_OVERHEAD + __PT_SIZE)

	j	4f

2:	UPDATE_VTIME %r14,%r15,__LC_SYNC_ENTER_TIMER

	BPENTER __TI_flags(%r12),_TIF_ISOLATE_BP

	lg	%r15,__LC_KERNEL_STACK

	lgr	%r14,%r12

	aghi	%r14,__TASK_thread	# pointer to thread_struct
@@ -729,7 +769,7 @@ ENTRY(io_int_handler) 
	mvc	__LC_RETURN_PSW(16),__PT_PSW(%r11)

	tm	__PT_PSW+1(%r11),0x01	# returning to user ?

	jno	.Lio_exit_kernel

	BPON

	BPEXIT	__TI_flags(%r12),_TIF_ISOLATE_BP

.Lio_exit_timer:

	stpt	__LC_EXIT_TIMER

	mvc	__VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
@@ -1165,7 +1205,7 @@ ENTRY(mcck_int_handler) 
	mvc	__LC_RETURN_MCCK_PSW(16),__PT_PSW(%r11) # move return PSW

	tm	__LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?

	jno	0f

	BPON

	BPEXIT	__TI_flags(%r12),_TIF_ISOLATE_BP

	stpt	__LC_EXIT_TIMER

	mvc	__VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER

0:	lmg	%r11,%r15,__PT_R11(%r11)
@@ -1292,7 +1332,8 @@ cleanup_critical: 
	clg     %r9,BASED(.Lsie_crit_mcck_length)

	jh      1f

	oi      __LC_CPU_FLAGS+7, _CIF_MCCK_GUEST

1:	lg	%r9,__SF_EMPTY(%r15)		# get control block pointer

1:	BPENTER __SF_EMPTY+24(%r15),(_TIF_ISOLATE_BP|_TIF_ISOLATE_BP_GUEST)

	lg	%r9,__SF_EMPTY(%r15)		# get control block pointer

	ni	__SIE_PROG0C+3(%r9),0xfe	# no longer in SIE

	lctlg	%c1,%c1,__LC_USER_ASCE		# load primary asce

	larl	%r9,sie_exit			# skip forward to sie_exit

arch/s390/kernel/processor.c

+18 −0
Original line number Diff line number Diff line
@@ -197,3 +197,21 @@ const struct seq_operations cpuinfo_op = { 
	.stop	= c_stop,

	.show	= show_cpuinfo,

};



int s390_isolate_bp(void)

{

	if (!test_facility(82))

		return -EOPNOTSUPP;

	set_thread_flag(TIF_ISOLATE_BP);

	return 0;

}

EXPORT_SYMBOL(s390_isolate_bp);



int s390_isolate_bp_guest(void)

{

	if (!test_facility(82))

		return -EOPNOTSUPP;

	set_thread_flag(TIF_ISOLATE_BP_GUEST);

	return 0;

}

EXPORT_SYMBOL(s390_isolate_bp_guest);