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// 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);
}
}
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