s390: add options to change branch prediction behaviour for the kernel (d768bd89) · Commits · 戴 / test

arch/s390/Kconfig

+17 −0

Original line number	Diff line number	Diff line
		@@ -540,6 +540,23 @@ config ARCH_RANDOM

		If unsure, say Y.

		config KERNEL_NOBP
		def_bool n
		prompt "Enable modified branch prediction for the kernel by default"
		help
		If this option is selected the kernel will switch to a modified
		branch prediction mode if the firmware interface is available.
		The modified branch prediction mode improves the behaviour in
		regard to speculative execution.

		With the option enabled the kernel parameter "nobp=0" or "nospec"
		can be used to run the kernel in the normal branch prediction mode.

		With the option disabled the modified branch prediction mode is
		enabled with the "nobp=1" kernel parameter.

		If unsure, say N.

		endmenu

		menu "Memory setup"

arch/s390/include/asm/processor.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -91,6 +91,7 @@ void cpu_detect_mhz_feature(void);
		extern const struct seq_operations cpuinfo_op;
		extern int sysctl_ieee_emulation_warnings;
		extern void execve_tail(void);
		extern void __bpon(void);

		/*
		* User space process size: 2GB for 31 bit, 4TB or 8PT for 64 bit.

arch/s390/kernel/alternative.c

+23 −0

Original line number	Diff line number	Diff line
		@@ -15,6 +15,29 @@ static int __init disable_alternative_instructions(char *str)

		early_param("noaltinstr", disable_alternative_instructions);

		static int __init nobp_setup_early(char *str)
		{
		bool enabled;
		int rc;

		rc = kstrtobool(str, &enabled);
		if (rc)
		return rc;
		if (enabled && test_facility(82))
		__set_facility(82, S390_lowcore.alt_stfle_fac_list);
		else
		__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
		return 0;
		}
		early_param("nobp", nobp_setup_early);

		static int __init nospec_setup_early(char *str)
		{
		__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
		return 0;
		}
		early_param("nospec", nospec_setup_early);

		struct brcl_insn {
		u16 opc;
		s32 disp;

arch/s390/kernel/early.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -196,6 +196,8 @@ static noinline __init void setup_facility_list(void)
		memcpy(S390_lowcore.alt_stfle_fac_list,
		S390_lowcore.stfle_fac_list,
		sizeof(S390_lowcore.alt_stfle_fac_list));
		if (!IS_ENABLED(CONFIG_KERNEL_NOBP))
		__clear_facility(82, S390_lowcore.alt_stfle_fac_list);
		}

		static __init void detect_diag9c(void)

arch/s390/kernel/entry.S

+48 −0

Original line number	Diff line number	Diff line
		@@ -159,6 +159,34 @@ _PIF_WORK = (_PIF_PER_TRAP \| _PIF_SYSCALL_RESTART)
		tm off+\addr, \mask
		.endm

		.macro BPOFF
		.pushsection .altinstr_replacement, "ax"
		660: .long 0xb2e8c000
		.popsection
		661: .long 0x47000000
		.pushsection .altinstructions, "a"
		.long 661b - .
		.long 660b - .
		.word 82
		.byte 4
		.byte 4
		.popsection
		.endm

		.macro BPON
		.pushsection .altinstr_replacement, "ax"
		662: .long 0xb2e8d000
		.popsection
		663: .long 0x47000000
		.pushsection .altinstructions, "a"
		.long 663b - .
		.long 662b - .
		.word 82
		.byte 4
		.byte 4
		.popsection
		.endm

		.section .kprobes.text, "ax"
		.Ldummy:
		/*
		@@ -171,6 +199,11 @@ _PIF_WORK = (_PIF_PER_TRAP \| _PIF_SYSCALL_RESTART)
		*/
		nop 0

		ENTRY(__bpon)
		.globl __bpon
		BPON
		br %r14

		/*
		* Scheduler resume function, called by switch_to
		* gpr2 = (task_struct *) prev
		@@ -226,8 +259,11 @@ ENTRY(sie64a)
		jnz .Lsie_skip
		TSTMSK __LC_CPU_FLAGS,_CIF_FPU
		jo .Lsie_skip # exit if fp/vx regs changed
		BPON
		.Lsie_entry:
		sie 0(%r14)
		.Lsie_exit:
		BPOFF
		.Lsie_skip:
		ni __SIE_PROG0C+3(%r14),0xfe # no longer in SIE
		lctlg %c1,%c1,__LC_USER_ASCE # load primary asce
		@@ -279,6 +315,7 @@ ENTRY(system_call)
		stpt __LC_SYNC_ENTER_TIMER
		.Lsysc_stmg:
		stmg %r8,%r15,__LC_SAVE_AREA_SYNC
		BPOFF
		lg %r12,__LC_CURRENT
		lghi %r13,__TASK_thread
		lghi %r14,_PIF_SYSCALL
		@@ -325,6 +362,7 @@ ENTRY(system_call)
		jnz .Lsysc_work # check for work
		TSTMSK __LC_CPU_FLAGS,_CIF_WORK
		jnz .Lsysc_work
		BPON
		.Lsysc_restore:
		lg %r14,__LC_VDSO_PER_CPU
		lmg %r0,%r10,__PT_R0(%r11)
		@@ -530,6 +568,7 @@ ENTRY(kernel_thread_starter)

		ENTRY(pgm_check_handler)
		stpt __LC_SYNC_ENTER_TIMER
		BPOFF
		stmg %r8,%r15,__LC_SAVE_AREA_SYNC
		lg %r10,__LC_LAST_BREAK
		lg %r12,__LC_CURRENT
		@@ -637,6 +676,7 @@ ENTRY(pgm_check_handler)
		ENTRY(io_int_handler)
		STCK __LC_INT_CLOCK
		stpt __LC_ASYNC_ENTER_TIMER
		BPOFF
		stmg %r8,%r15,__LC_SAVE_AREA_ASYNC
		lg %r12,__LC_CURRENT
		larl %r13,cleanup_critical
		@@ -687,9 +727,13 @@ ENTRY(io_int_handler)
		lg %r14,__LC_VDSO_PER_CPU
		lmg %r0,%r10,__PT_R0(%r11)
		mvc __LC_RETURN_PSW(16),__PT_PSW(%r11)
		tm __PT_PSW+1(%r11),0x01 # returning to user ?
		jno .Lio_exit_kernel
		BPON
		.Lio_exit_timer:
		stpt __LC_EXIT_TIMER
		mvc __VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
		.Lio_exit_kernel:
		lmg %r11,%r15,__PT_R11(%r11)
		lpswe __LC_RETURN_PSW
		.Lio_done:
		@@ -860,6 +904,7 @@ ENTRY(io_int_handler)
		ENTRY(ext_int_handler)
		STCK __LC_INT_CLOCK
		stpt __LC_ASYNC_ENTER_TIMER
		BPOFF
		stmg %r8,%r15,__LC_SAVE_AREA_ASYNC
		lg %r12,__LC_CURRENT
		larl %r13,cleanup_critical
		@@ -908,6 +953,7 @@ ENTRY(psw_idle)
		.Lpsw_idle_stcctm:
		#endif
		oi __LC_CPU_FLAGS+7,_CIF_ENABLED_WAIT
		BPON
		STCK __CLOCK_IDLE_ENTER(%r2)
		stpt __TIMER_IDLE_ENTER(%r2)
		.Lpsw_idle_lpsw:
		@@ -1008,6 +1054,7 @@ load_fpu_regs:
		*/
		ENTRY(mcck_int_handler)
		STCK __LC_MCCK_CLOCK
		BPOFF
		la %r1,4095 # validate r1
		spt __LC_CPU_TIMER_SAVE_AREA-4095(%r1) # validate cpu timer
		sckc __LC_CLOCK_COMPARATOR # validate comparator
		@@ -1118,6 +1165,7 @@ 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
		stpt __LC_EXIT_TIMER
		mvc __VDSO_ECTG_BASE(16,%r14),__LC_EXIT_TIMER
		0: lmg %r11,%r15,__PT_R11(%r11)

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