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

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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: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
This commit is contained in:
Pawan Gupta
2019-10-23 11:01:53 +02:00
committed by Thomas Gleixner
parent 286836a704
commit 95c5824f75
6 changed files with 175 additions and 1 deletions
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16
arch/x86/kernel/cpu/cpu.h
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@@ -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);