From: Huang Rui <[email protected]>
AMD Carrizo processors (Family 15h, Models 60h-6fh) add 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 <[email protected]>
Cc: Aaron Lu <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Andreas Herrmann <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Dave Hansen <[email protected]>
Cc: Dirk Brandewie <[email protected]>
Cc: Fengguang Wu <[email protected]>
Cc: Frédéric Weisbecker <[email protected]>
Cc: "H. Peter Anvin" <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: John Stultz <[email protected]>
Cc: Josh Triplett <[email protected]>
Cc: Len Brown <[email protected]>
Cc: Mike Galbraith <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Cc: Ross Zwisler <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Tony Li <[email protected]>
Cc: x86-ml <[email protected]>
Link:
http://lkml.kernel.org/r/[email protected]
Signed-off-by: Borislav Petkov <[email protected]>
---
arch/x86/include/asm/cpufeature.h | 1 +
arch/x86/include/asm/mwait.h | 45 +++++++++++++++++++++++++++++++++++++++
2 files changed, 46 insertions(+)
diff --git a/arch/x86/include/asm/cpufeature.h
b/arch/x86/include/asm/cpufeature.h
index 3d6606fb97d0..a39e5708209b 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -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
diff --git a/arch/x86/include/asm/mwait.h b/arch/x86/include/asm/mwait.h
index 653dfa7662e1..c70689b5e5aa 100644
--- a/arch/x86/include/asm/mwait.h
+++ b/arch/x86/include/asm/mwait.h
@@ -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();
--
2.5.0.rc2.28.g6003e7f
--
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