[mirror_ubuntu-bionic-kernel.git] / arch / x86 / kernel / cpu / tsx.c

// SPDX-License-Identifier: GPL-2.0
/*
 * Intel Transactional Synchronization Extensions (TSX) control.
 *
 * Copyright (C) 2019 Intel Corporation
 *
 * Author:
 *	Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
 */

#include <linux/cpufeature.h>

#include <asm/cmdline.h>

#include "cpu.h"

enum tsx_ctrl_states tsx_ctrl_state __ro_after_init = TSX_CTRL_NOT_SUPPORTED;

void tsx_disable(void)
{
	u64 tsx;

	rdmsrl(MSR_IA32_TSX_CTRL, tsx);

	/* Force all transactions to immediately abort */
	tsx |= TSX_CTRL_RTM_DISABLE;

	/*
	 * Ensure TSX support is not enumerated in CPUID.
	 * This is visible to userspace and will ensure they
	 * do not waste resources trying TSX transactions that
	 * will always abort.
	 */
	tsx |= TSX_CTRL_CPUID_CLEAR;

	wrmsrl(MSR_IA32_TSX_CTRL, tsx);
}

void tsx_enable(void)
{
	u64 tsx;

	rdmsrl(MSR_IA32_TSX_CTRL, tsx);

	/* Enable the RTM feature in the cpu */
	tsx &= ~TSX_CTRL_RTM_DISABLE;

	/*
	 * Ensure TSX support is enumerated in CPUID.
	 * This is visible to userspace and will ensure they
	 * can enumerate and use the TSX feature.
	 */
	tsx &= ~TSX_CTRL_CPUID_CLEAR;

	wrmsrl(MSR_IA32_TSX_CTRL, tsx);
}

static bool __init tsx_ctrl_is_supported(void)
{
	u64 ia32_cap = x86_read_arch_cap_msr();

	/*
	 * TSX is controlled via MSR_IA32_TSX_CTRL.  However, support for this
	 * MSR is enumerated by ARCH_CAP_TSX_MSR bit in MSR_IA32_ARCH_CAPABILITIES.
	 *
	 * TSX control (aka MSR_IA32_TSX_CTRL) is only available after a
	 * microcode update on CPUs that have their MSR_IA32_ARCH_CAPABILITIES
	 * bit MDS_NO=1. CPUs with MDS_NO=0 are not planned to get
	 * MSR_IA32_TSX_CTRL support even after a microcode update. Thus,
	 * tsx= cmdline requests will do nothing on CPUs without
	 * MSR_IA32_TSX_CTRL support.
	 */
	return !!(ia32_cap & ARCH_CAP_TSX_CTRL_MSR);
}

void __init tsx_init(void)
{
	char arg[4] = {};
	int ret;

	if (!tsx_ctrl_is_supported())
		return;

	ret = cmdline_find_option(boot_command_line, "tsx", arg, sizeof(arg));
	if (ret >= 0) {
		if (!strcmp(arg, "on")) {
			tsx_ctrl_state = TSX_CTRL_ENABLE;
		} else if (!strcmp(arg, "off")) {
			tsx_ctrl_state = TSX_CTRL_DISABLE;
		} else {
			tsx_ctrl_state = TSX_CTRL_DISABLE;
			pr_err("tsx: invalid option, defaulting to off\n");
		}
	} else {
		/* tsx= not provided, defaulting to off */
		tsx_ctrl_state = TSX_CTRL_DISABLE;
	}

	if (tsx_ctrl_state == TSX_CTRL_DISABLE) {
		tsx_disable();

		/*
		 * tsx_disable() will change the state of the
		 * RTM CPUID bit.  Clear it here since it is now
		 * expected to be not set.
		 */
		setup_clear_cpu_cap(X86_FEATURE_RTM);
	} else if (tsx_ctrl_state == TSX_CTRL_ENABLE) {

		/*
		 * HW defaults TSX to be enabled at bootup.
		 * We may still need the TSX enable support
		 * during init for special cases like
		 * kexec after TSX is disabled.
		 */
		tsx_enable();

		/*
		 * tsx_enable() will change the state of the
		 * RTM CPUID bit.  Force it here since it is now
		 * expected to be set.
		 */
		setup_force_cpu_cap(X86_FEATURE_RTM);
	}
}
Commit	Line	Data
8167aae6 PG	1	// SPDX-License-Identifier: GPL-2.0
	2	/*
	3	* Intel Transactional Synchronization Extensions (TSX) control.
	4	*
	5	* Copyright (C) 2019 Intel Corporation
	6	*
	7	* Author:
	8	* Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
	9	*/
	10
	11	#include <linux/cpufeature.h>
	12
	13	#include <asm/cmdline.h>
	14
	15	#include "cpu.h"
	16
	17	enum tsx_ctrl_states tsx_ctrl_state __ro_after_init = TSX_CTRL_NOT_SUPPORTED;
	18
	19	void tsx_disable(void)
	20	{
	21	u64 tsx;
	22
	23	rdmsrl(MSR_IA32_TSX_CTRL, tsx);
	24
	25	/* Force all transactions to immediately abort */
	26	tsx \|= TSX_CTRL_RTM_DISABLE;
	27
	28	/*
	29	* Ensure TSX support is not enumerated in CPUID.
	30	* This is visible to userspace and will ensure they
	31	* do not waste resources trying TSX transactions that
	32	* will always abort.
	33	*/
	34	tsx \|= TSX_CTRL_CPUID_CLEAR;
	35
	36	wrmsrl(MSR_IA32_TSX_CTRL, tsx);
	37	}
	38
	39	void tsx_enable(void)
	40	{
	41	u64 tsx;
	42
	43	rdmsrl(MSR_IA32_TSX_CTRL, tsx);
	44
	45	/* Enable the RTM feature in the cpu */
	46	tsx &= ~TSX_CTRL_RTM_DISABLE;
	47
	48	/*
	49	* Ensure TSX support is enumerated in CPUID.
	50	* This is visible to userspace and will ensure they
	51	* can enumerate and use the TSX feature.
	52	*/
	53	tsx &= ~TSX_CTRL_CPUID_CLEAR;
	54
	55	wrmsrl(MSR_IA32_TSX_CTRL, tsx);
	56	}
	57
	58	static bool __init tsx_ctrl_is_supported(void)
	59	{
	60	u64 ia32_cap = x86_read_arch_cap_msr();
	61
	62	/*
	63	* TSX is controlled via MSR_IA32_TSX_CTRL. However, support for this
	64	* MSR is enumerated by ARCH_CAP_TSX_MSR bit in MSR_IA32_ARCH_CAPABILITIES.
65	*
66	* TSX control (aka MSR_IA32_TSX_CTRL) is only available after a
67	* microcode update on CPUs that have their MSR_IA32_ARCH_CAPABILITIES
68	* bit MDS_NO=1. CPUs with MDS_NO=0 are not planned to get
69	* MSR_IA32_TSX_CTRL support even after a microcode update. Thus,
70	* tsx= cmdline requests will do nothing on CPUs without
71	* MSR_IA32_TSX_CTRL support.
72	*/
73	return !!(ia32_cap & ARCH_CAP_TSX_CTRL_MSR);
74	}
75
76	void __init tsx_init(void)
77	{
78	char arg[4] = {};
79	int ret;
80
81	if (!tsx_ctrl_is_supported())
82	return;
83
84	ret = cmdline_find_option(boot_command_line, "tsx", arg, sizeof(arg));
85	if (ret >= 0) {
86	if (!strcmp(arg, "on")) {
87	tsx_ctrl_state = TSX_CTRL_ENABLE;
88	} else if (!strcmp(arg, "off")) {
89	tsx_ctrl_state = TSX_CTRL_DISABLE;
90	} else {
91	tsx_ctrl_state = TSX_CTRL_DISABLE;
92	pr_err("tsx: invalid option, defaulting to off\n");
93	}
94	} else {
95	/* tsx= not provided, defaulting to off */
96	tsx_ctrl_state = TSX_CTRL_DISABLE;
97	}
98
99	if (tsx_ctrl_state == TSX_CTRL_DISABLE) {
100	tsx_disable();
101
102	/*
103	* tsx_disable() will change the state of the
104	* RTM CPUID bit. Clear it here since it is now
105	* expected to be not set.
106	*/
107	setup_clear_cpu_cap(X86_FEATURE_RTM);
108	} else if (tsx_ctrl_state == TSX_CTRL_ENABLE) {
109
110	/*
111	* HW defaults TSX to be enabled at bootup.
112	* We may still need the TSX enable support
113	* during init for special cases like
114	* kexec after TSX is disabled.
115	*/
116	tsx_enable();
117
118	/*
119	* tsx_enable() will change the state of the
120	* RTM CPUID bit. Force it here since it is now
121	* expected to be set.
122	*/
123	setup_force_cpu_cap(X86_FEATURE_RTM);
124	}
125	}