linux/arch/x86/include/uapi/asm/hwcap2.h

#ifndef _ASM_X86_HWCAP2_H
#define _ASM_X86_HWCAP2_H

/* MONITOR/MWAIT enabled in Ring 3 */
#define HWCAP2_RING3MWAIT		(1 << 0)

#endif
x86/elf: Add HWCAP2 to expose ring 3 MONITOR/MWAIT Introduce ELF_HWCAP2 variable for x86 and reserve its bit 0 to expose the ring 3 MONITOR/MWAIT. HWCAP variables contain bitmasks which can be used by userspace applications to detect which instruction sets are supported by CPU. On x86 architecture information about CPU capabilities can be checked via CPUID instructions, unfortunately presence of ring 3 MONITOR/MWAIT feature cannot be checked this way. ELF_HWCAP cannot be used as well, because on x86 it is set to CPUID[1].EDX which means that all bits are reserved there. HWCAP2 approach was chosen because it reuses existing solution present in other architectures, so only minor modifications are required to the kernel and userspace applications. When ELF_HWCAP2 is defined kernel maps it to AT_HWCAP2 during the start of the application. This way the ring 3 MONITOR/MWAIT feature can be detected using getauxval() API in a simple and fast manner. ELF_HWCAP2 type is u32 to be consistent with x86 ELF_HWCAP type. Signed-off-by: Grzegorz Andrejczuk <grzegorz.andrejczuk@intel.com> Cc: Piotr.Luc@intel.com Cc: dave.hansen@linux.intel.com Link: http://lkml.kernel.org/r/1484918557-15481-3-git-send-email-grzegorz.andrejczuk@intel.com Signed-off-by: Thomas Gleixner <tglx@linutronix.de> 2017-01-20 13:22:34 +00:00			`#ifndef _ASM_X86_HWCAP2_H`
			`#define _ASM_X86_HWCAP2_H`

			`/* MONITOR/MWAIT enabled in Ring 3 */`
			`#define HWCAP2_RING3MWAIT (1 << 0)`

			`#endif`