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/* SPDX-License-Identifier: GPL-2.0 */
#ifndef _ASM_X86_MWAIT_H
#define _ASM_X86_MWAIT_H
#include <linux/sched.h>
#include <linux/sched/idle.h>
#include <asm/cpufeature.h>
#include <asm/nospec-branch.h>
#define MWAIT_SUBSTATE_MASK 0xf
#define MWAIT_CSTATE_MASK 0xf
#define MWAIT_SUBSTATE_SIZE 4
#define MWAIT_HINT2CSTATE(hint) (((hint) >> MWAIT_SUBSTATE_SIZE) & MWAIT_CSTATE_MASK)
#define MWAIT_HINT2SUBSTATE(hint) ((hint) & MWAIT_CSTATE_MASK)
#define MWAIT_C1_SUBSTATE_MASK 0xf0
#define CPUID_MWAIT_LEAF 5
#define CPUID5_ECX_EXTENSIONS_SUPPORTED 0x1
#define CPUID5_ECX_INTERRUPT_BREAK 0x2
#define MWAIT_ECX_INTERRUPT_BREAK 0x1
#define MWAITX_ECX_TIMER_ENABLE BIT(1)
#define MWAITX_MAX_WAIT_CYCLES UINT_MAX
#define MWAITX_DISABLE_CSTATES 0xf0
#define TPAUSE_C01_STATE 1
#define TPAUSE_C02_STATE 0
static __always_inline void __monitor(const void *eax, unsigned long ecx,
unsigned long edx)
{
/* "monitor %eax, %ecx, %edx;" */
asm volatile(".byte 0x0f, 0x01, 0xc8;"
:: "a" (eax), "c" (ecx), "d"(edx));
}
static __always_inline void __monitorx(const void *eax, unsigned long ecx,
unsigned long edx)
{
/* "monitorx %eax, %ecx, %edx;" */
asm volatile(".byte 0x0f, 0x01, 0xfa;"
:: "a" (eax), "c" (ecx), "d"(edx));
}
static __always_inline void __mwait(unsigned long eax, unsigned long ecx)
{
mds_idle_clear_cpu_buffers();
/* "mwait %eax, %ecx;" */
asm volatile(".byte 0x0f, 0x01, 0xc9;"
:: "a" (eax), "c" (ecx));
}
/*
* MWAITX allows for a timer expiration to get the core out a wait state in
* addition to the default MWAIT exit condition of a store appearing at a
* monitored virtual address.
*
* Registers:
*
* MWAITX ECX[1]: enable timer if set
* MWAITX EBX[31:0]: max wait time expressed in SW P0 clocks. The software P0
* frequency is the same as the TSC frequency.
*
* Below is a comparison between MWAIT and MWAITX on AMD processors:
*
* MWAIT MWAITX
* opcode 0f 01 c9 | 0f 01 fb
* ECX[0] value of RFLAGS.IF seen by instruction
* ECX[1] unused/#GP if set | enable timer if set
* ECX[31:2] unused/#GP if set
* EAX unused (reserve for hint)
* EBX[31:0] unused | max wait time (P0 clocks)
*
* MONITOR MONITORX
* opcode 0f 01 c8 | 0f 01 fa
* EAX (logical) address to monitor
* ECX #GP if not zero
*/
static __always_inline void __mwaitx(unsigned long eax, unsigned long ebx,
unsigned long ecx)
{
/* No MDS buffer clear as this is AMD/HYGON only */
/* "mwaitx %eax, %ebx, %ecx;" */
asm volatile(".byte 0x0f, 0x01, 0xfb;"
:: "a" (eax), "b" (ebx), "c" (ecx));
}
/*
* Re-enable interrupts right upon calling mwait in such a way that
* no interrupt can fire _before_ the execution of mwait, ie: no
* instruction must be placed between "sti" and "mwait".
*
* This is necessary because if an interrupt queues a timer before
* executing mwait, it would otherwise go unnoticed and the next tick
* would not be reprogrammed accordingly before mwait ever wakes up.
*/
static __always_inline void __sti_mwait(unsigned long eax, unsigned long ecx)
{
mds_idle_clear_cpu_buffers();
/* "mwait %eax, %ecx;" */
asm volatile("sti; .byte 0x0f, 0x01, 0xc9;"
:: "a" (eax), "c" (ecx));
}
/*
* This uses new MONITOR/MWAIT instructions on P4 processors with PNI,
* which can obviate IPI to trigger checking of need_resched.
* We execute MONITOR against need_resched and enter optimized wait state
* through MWAIT. Whenever someone changes need_resched, we would be woken
* up from MWAIT (without an IPI).
*
* New with Core Duo processors, MWAIT can take some hints based on CPU
* capability.
*/
static __always_inline void mwait_idle_with_hints(unsigned long eax, unsigned long ecx)
{
if (static_cpu_has_bug(X86_BUG_MONITOR) || !current_set_polling_and_test()) {
if (static_cpu_has_bug(X86_BUG_CLFLUSH_MONITOR)) {
mb();
clflush((void *)¤t_thread_info()->flags);
mb();
}
__monitor((void *)¤t_thread_info()->flags, 0, 0);
if (!need_resched()) {
if (ecx & 1) {
__mwait(eax, ecx);
} else {
__sti_mwait(eax, ecx);
raw_local_irq_disable();
}
}
}
current_clr_polling();
}
/*
* Caller can specify whether to enter C0.1 (low latency, less
* power saving) or C0.2 state (saves more power, but longer wakeup
* latency). This may be overridden by the IA32_UMWAIT_CONTROL MSR
* which can force requests for C0.2 to be downgraded to C0.1.
*/
static inline void __tpause(u32 ecx, u32 edx, u32 eax)
{
/* "tpause %ecx, %edx, %eax;" */
#ifdef CONFIG_AS_TPAUSE
asm volatile("tpause %%ecx\n"
:
: "c"(ecx), "d"(edx), "a"(eax));
#else
asm volatile(".byte 0x66, 0x0f, 0xae, 0xf1\t\n"
:
: "c"(ecx), "d"(edx), "a"(eax));
#endif
}
#endif /* _ASM_X86_MWAIT_H */