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x86/asm: Add MONITORX/MWAITX instruction support

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AMD Carrizo processors (Family 15h, Models 60h-6fh) added a new
feature called MWAITX (MWAIT with extensions) as an extension to
MONITOR/MWAIT.

This new instruction controls a configurable timer which causes
the core to exit wait state on timer expiration, in addition to
"normal" MWAIT condition of reading from a monitored VA.

Compared to MONITOR/MWAIT, there are minor differences in opcode
and input parameters:

MWAITX ECX[1]: enable timer if set
MWAITX EBX[31:0]: max wait time expressed in SW P0 clocks ==
TSC. The software P0 frequency is the same as the TSC frequency.

                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 (SW P0 == TSC)

                MONITOR                         MONITORX
opcode          0f 01 c8           |            0f 01 fa
EAX                     (logical) address to monitor
ECX                     #GP if not zero

Max timeout = EBX/(TSC frequency)

Signed-off-by: Huang Rui <ray.huang@amd.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: Aaron Lu <aaron.lu@intel.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andreas Herrmann <herrmann.der.user@gmail.com>
Cc: Andy Lutomirski <luto@amacapital.net>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Dirk Brandewie <dirk.j.brandewie@intel.com>
Cc: Fengguang Wu <fengguang.wu@intel.com>
Cc: Frédéric Weisbecker <fweisbec@gmail.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Len Brown <lenb@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Rafael J. Wysocki <rjw@rjwysocki.net>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tony Li <tony.li@amd.com>
Link: http://lkml.kernel.org/r/1439201994-28067-3-git-send-email-bp@alien8.de
Signed-off-by: Ingo Molnar <mingo@kernel.org>
This commit is contained in:
Huang Rui
2015-08-10 12:19:53 +02:00
committed by Ingo Molnar
parent f0a97af83f
commit f96756746c
2 changed files with 46 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

1
arch/x86/include/asm/cpufeature.h
View File

@@ -176,6 +176,7 @@
#define X86_FEATURE_PERFCTR_NB ( 6*32+24) /* NB performance counter extensions */
#define X86_FEATURE_BPEXT (6*32+26) /* data breakpoint extension */
#define X86_FEATURE_PERFCTR_L2 ( 6*32+28) /* L2 performance counter extensions */
#define X86_FEATURE_MWAITX ( 6*32+29) /* MWAIT extension (MONITORX/MWAITX) */
/*
* Auxiliary flags: Linux defined - For features scattered in various

45
arch/x86/include/asm/mwait.h
View File

@@ -14,6 +14,9 @@
#define CPUID5_ECX_INTERRUPT_BREAK 0x2
#define MWAIT_ECX_INTERRUPT_BREAK 0x1
#define MWAITX_ECX_TIMER_ENABLE BIT(1)
#define MWAITX_MAX_LOOPS ((u32)-1)
#define MWAITX_DISABLE_CSTATES 0xf
static inline void __monitor(const void *eax, unsigned long ecx,
unsigned long edx)
@@ -23,6 +26,14 @@ static inline void __monitor(const void *eax, unsigned long ecx,
:: "a" (eax), "c" (ecx), "d"(edx));
}
static 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 inline void __mwait(unsigned long eax, unsigned long ecx)
{
/* "mwait %eax, %ecx;" */
@@ -30,6 +41,40 @@ static inline void __mwait(unsigned long eax, unsigned long ecx)
:: "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 inline void __mwaitx(unsigned long eax, unsigned long ebx,
unsigned long ecx)
{
/* "mwaitx %eax, %ebx, %ecx;" */
asm volatile(".byte 0x0f, 0x01, 0xfb;"
:: "a" (eax), "b" (ebx), "c" (ecx));
}
static inline void __sti_mwait(unsigned long eax, unsigned long ecx)
{
trace_hardirqs_on();