Commit 95c5824f authored by Pawan Gupta's avatar Pawan Gupta Committed by Thomas Gleixner
Browse files

x86/cpu: Add a "tsx=" cmdline option with TSX disabled by default 



Add a kernel cmdline parameter "tsx" to control the Transactional
Synchronization Extensions (TSX) feature. On CPUs that support TSX
control, use "tsx=on|off" to enable or disable TSX. Not specifying this
option is equivalent to "tsx=off". This is because on certain processors
TSX may be used as a part of a speculative side channel attack.

Carve out the TSX controlling functionality into a separate compilation
unit because TSX is a CPU feature while the TSX async abort control
machinery will go to cpu/bugs.c.

 [ bp: - Massage, shorten and clear the arg buffer.
       - Clarifications of the tsx= possible options - Josh.
       - Expand on TSX_CTRL availability - Pawan. ]

Signed-off-by: default avatarPawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: default avatarBorislav Petkov <bp@suse.de>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarJosh Poimboeuf <jpoimboe@redhat.com>
parent 286836a7

Documentation/admin-guide/kernel-parameters.txt

+26 −0
Original line number Diff line number Diff line
@@ -4848,6 +4848,32 @@ 
			interruptions from clocksource watchdog are not

			acceptable).



	tsx=		[X86] Control Transactional Synchronization

			Extensions (TSX) feature in Intel processors that

			support TSX control.



			This parameter controls the TSX feature. The options are:



			on	- Enable TSX on the system. Although there are

				mitigations for all known security vulnerabilities,

				TSX has been known to be an accelerator for

				several previous speculation-related CVEs, and

				so there may be unknown	security risks associated

				with leaving it enabled.



			off	- Disable TSX on the system. (Note that this

				option takes effect only on newer CPUs which are

				not vulnerable to MDS, i.e., have

				MSR_IA32_ARCH_CAPABILITIES.MDS_NO=1 and which get

				the new IA32_TSX_CTRL MSR through a microcode

				update. This new MSR allows for the reliable

				deactivation of the TSX functionality.)



			Not specifying this option is equivalent to tsx=off.



			See Documentation/admin-guide/hw-vuln/tsx_async_abort.rst

			for more details.



	turbografx.map[2|3]=	[HW,JOY]

			TurboGraFX parallel port interface

			Format:

arch/x86/kernel/cpu/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -30,7 +30,7 @@ obj-$(CONFIG_PROC_FS) += proc.o 
obj-$(CONFIG_X86_FEATURE_NAMES) += capflags.o powerflags.o



ifdef CONFIG_CPU_SUP_INTEL

obj-y			+= intel.o intel_pconfig.o

obj-y			+= intel.o intel_pconfig.o tsx.o

obj-$(CONFIG_PM)	+= intel_epb.o

endif

obj-$(CONFIG_CPU_SUP_AMD)		+= amd.o

arch/x86/kernel/cpu/common.c

+2 −0
Original line number Diff line number Diff line
@@ -1561,6 +1561,8 @@ void __init identify_boot_cpu(void) 
#endif

	cpu_detect_tlb(&boot_cpu_data);

	setup_cr_pinning();



	tsx_init();

}



void identify_secondary_cpu(struct cpuinfo_x86 *c)

arch/x86/kernel/cpu/cpu.h

+16 −0
Original line number Diff line number Diff line
@@ -44,6 +44,22 @@ struct _tlb_table { 
extern const struct cpu_dev *const __x86_cpu_dev_start[],

			    *const __x86_cpu_dev_end[];



#ifdef CONFIG_CPU_SUP_INTEL

enum tsx_ctrl_states {

	TSX_CTRL_ENABLE,

	TSX_CTRL_DISABLE,

	TSX_CTRL_NOT_SUPPORTED,

};



extern __ro_after_init enum tsx_ctrl_states tsx_ctrl_state;



extern void __init tsx_init(void);

extern void tsx_enable(void);

extern void tsx_disable(void);

#else

static inline void tsx_init(void) { }

#endif /* CONFIG_CPU_SUP_INTEL */



extern void get_cpu_cap(struct cpuinfo_x86 *c);

extern void get_cpu_address_sizes(struct cpuinfo_x86 *c);

extern void cpu_detect_cache_sizes(struct cpuinfo_x86 *c);

arch/x86/kernel/cpu/intel.c

+5 −0
Original line number Diff line number Diff line
@@ -762,6 +762,11 @@ static void init_intel(struct cpuinfo_x86 *c) 
		detect_tme(c);



	init_intel_misc_features(c);



	if (tsx_ctrl_state == TSX_CTRL_ENABLE)

		tsx_enable();

	if (tsx_ctrl_state == TSX_CTRL_DISABLE)

		tsx_disable();

}



#ifdef CONFIG_X86_32

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