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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>
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savings and to improve performance
In Linux-3.9 we removed the mwait_idle() loop:
69fb3676df33 ("x86 idle: remove mwait_idle() and "idle=mwait" cmdline param")
The reasoning was that modern machines should be sufficiently
happy during the boot process using the default_idle() HALT
loop, until cpuidle loads and either acpi_idle or intel_idle
invoke the newer MWAIT-with-hints idle loop.
But two machines reported problems:
1. Certain Core2-era machines support MWAIT-C1 and HALT only.
MWAIT-C1 is preferred for optimal power and performance.
But if they support just C1, cpuidle never loads and
so they use the boot-time default idle loop forever.
2. Some laptops will boot-hang if HALT is used,
but will boot successfully if MWAIT is used.
This appears to be a hidden assumption in BIOS SMI,
that is presumably valid on the proprietary OS
where the BIOS was validated.
https://bugzilla.kernel.org/show_bug.cgi?id=60770
So here we effectively revert the patch above, restoring
the mwait_idle() loop. However, we don't bother restoring
the idle=mwait cmdline parameter, since it appears to add
no value.
Maintainer notes:
For 3.9, simply revert 69fb3676df
for 3.10, patch -F3 applies, fuzz needed due to __cpuinit use in
context For 3.11, 3.12, 3.13, this patch applies cleanly
Tested-by: Mike Galbraith <bitbucket@online.de>
Signed-off-by: Len Brown <len.brown@intel.com>
Acked-by: Mike Galbraith <bitbucket@online.de>
Cc: <stable@vger.kernel.org> # 3.9+
Cc: Borislav Petkov <bp@alien8.de>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ian Malone <ibmalone@gmail.com>
Cc: Josh Boyer <jwboyer@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Link: http://lkml.kernel.org/r/345254a551eb5a6a866e048d7ab570fd2193aca4.1389763084.git.len.brown@intel.com
[ Ported to recent kernels. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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X86_FEATURE_FXSAVE_LEAK, X86_FEATURE_11AP and
X86_FEATURE_CLFLUSH_MONITOR are not really features but synthetic bits
we use for applying different bug workarounds. Call them what they
really are, and make sure they get the proper cross-CPU behavior (OR
rather than AND).
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1403042783-23278-1-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
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With various drivers wanting to inject idle time; we get people
calling idle routines outside of the idle loop proper.
Therefore we need to be extra careful about not missing
TIF_NEED_RESCHED -> PREEMPT_NEED_RESCHED propagations.
While looking at this, I also realized there's a small window in the
existing idle loop where we can miss TIF_NEED_RESCHED; when it hits
right after the tif_need_resched() test at the end of the loop but
right before the need_resched() test at the start of the loop.
So move preempt_fold_need_resched() out of the loop where we're
guaranteed to have TIF_NEED_RESCHED set.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/n/tip-x9jgh45oeayzajz2mjt0y7d6@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Use static_cpu_has() to conditionalize the CLFLUSH workaround, and add
memory barriers around it since the documentation is explicit that
CLFLUSH is only ordered with respect to MFENCE.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Len Brown <len.brown@intel.com>
Link: http://lkml.kernel.org/r/CA%2B55aFzGxcML7j8CEvQPYzh0W81uVoAAVmGctMOUZ7CZ1yYd2A@mail.gmail.com
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People seem to delight in writing wrong and broken mwait idle routines;
collapse the lot.
This leaves mwait_play_dead() the sole remaining user of __mwait() and
new __mwait() users are probably doing it wrong.
Also remove __sti_mwait() as its unused.
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: Jacob Jun Pan <jacob.jun.pan@linux.intel.com>
Cc: Mike Galbraith <bitbucket@online.de>
Cc: Len Brown <lenb@kernel.org>
Cc: Rui Zhang <rui.zhang@intel.com>
Acked-by: Rafael Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20131212141654.616820819@infradead.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
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Remove the assumption that cstate_tables are
indexed by MWAIT flag values. Each entry
identifies itself via its own flags value.
This change is needed to support multiple states
that share the same MWAIT flags.
Note that this can have an effect on what state is described
by 'N' on cmdline intel_idle.max_cstate=N on some systems.
intel_idle.max_cstate=0 still disables the driver
intel_idle.max_cstate=1 still results in just C1(E)
However, "place holders" in the sparse C-state name-space
(eg. Atom) have been removed.
Signed-off-by: Len Brown <len.brown@intel.com>
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Cosmetic only.
Replace use of MWAIT_MAX_NUM_CSTATES with CPUIDLE_STATE_MAX.
They are both 8, so this patch has no functional change.
The reason to change is that intel_idle will soon be able
to export more than the 8 "major" states supported by MWAIT.
When we hit that limit, it is important to know
where the limit comes from.
Signed-off-by: Len Brown <len.brown@intel.com>
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We have MWAIT constants spread across three different .c files, for no
good reason. Move them all into a common header file.
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Reviewed-by: Arjan van de Ven <arjan@linux.intel.com>
Cc: Len Brown <lenb@kernel.org>
LKML-Reference: <tip-*@git.kernel.org>
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