Currently the option resides under X86_EXTENDED_PLATFORM due to historical
nonstandard A20M# handling. However that is no longer the case and so Elan can
be treated as part of the standard processor choice Kconfig option.
Signed-off-by: NIan Campbell <ian.campbell@citrix.com>
Link: http://lkml.kernel.org/r/1302245177.31620.47.camel@localhost.localdomain
Cc: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: NH. Peter Anvin <hpa@linux.intel.com>

On i386 (not x86_64) early implementations of gcc would have a bug
with asm goto causing it to produce code like the following:

(This was noticed by Peter Zijlstra)

   56 pushl 0
   67 nopl         jmp 0x6f
      popl
      jmp 0x8c

   6f              mov
                   test
                   je 0x8c

   8c mov
      call *(%esp)

The jump added in the asm goto skipped over the popl that matched
the pushl 0, which lead up to a quick crash of the system when
the jump was enabled. The nopl is defined in the asm goto () statement
and when tracepoints are enabled, the nop changes to a jump to the label
that was specified by the asm goto. asm goto is suppose to tell gcc that
the code in the asm might jump to an external label. Here gcc obviously
fails to make that work.

The bug report for gcc is here:

  http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46226

The bug only appears on x86 when not compiled with
-maccumulate-outgoing-args. This option is always set on x86_64 and it
is also the work around for a function graph tracer i386 bug.
(See commit: 746357d6)
This explains why the bug only showed up on i386 when function graph
tracer was not enabled.

This patch now adds a CONFIG_JUMP_LABEL option that is default
off instead of using jump labels by default. When jump labels are
enabled, the -maccumulate-outgoing-args will be used (causing a
slightly larger kernel image on i386). This option will exist
until we have a way to detect if the gcc compiler in use is safe
to use on all configurations without the work around.

Note, there exists such a test, but for now we will keep the enabling
of jump label as a manual option.

Archs that know the compiler is safe with asm goto, may choose to
select JUMP_LABEL and enable it by default.
Reported-by: NIngo Molnar <mingo@elte.hu>
Cause-discovered-by: NPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Jason Baron <jbaron@redhat.com>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: David Daney <ddaney@caviumnetworks.com>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: David Miller <davem@davemloft.net>
Cc: Richard Henderson <rth@redhat.com>
LKML-Reference: <1288028746.3673.11.camel@laptop>
Signed-off-by: NSteven Rostedt <rostedt@goodmis.org>

commit 746357d6 (x86: Prevent GCC 4.4.x (pentium-mmx et al) function
prologue wreckage) uses -mtune=generic to work around the function
prologue problem with mcount on -march=pentium-mmx and others.

Jakub pointed out that we can use -maccumulate-outgoing-args instead
which is selected by -mtune=generic and prevents the problem without
losing the -march specific optimizations.
Pointed-out-by: NJakub Jelinek <jakub@redhat.com>
Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: stable@kernel.org

When the kernel is compiled with -pg for tracing GCC 4.4.x inserts
stack alignment of a function _before_ the mcount prologue if the
-march=pentium-mmx is set and -mtune=generic is not set. This breaks
the assumption of the function graph tracer which expects that the
mcount prologue

       push %ebp
       mov  %esp, %ebp

is the first stack operation in a function because it needs to modify
the function return address on the stack to trap into the tracer
before returning to the real caller.

The generated code is:

        push   %edi
        lea    0x8(%esp),%edi
        and    $0xfffffff0,%esp
        pushl  -0x4(%edi)
        push   %ebp
        mov    %esp,%ebp

so the tracer modifies the copy of the return address which is stored
after the stack alignment and therefor does not trap the return which
in turn breaks the call chain logic of the tracer and leads to a
kernel panic.

Aside of the fact that the generated code is horrible for no good
reason other -march -mtune options generate the expected:

        push   %ebp
        mov    %esp,%ebp
        and    $0xfffffff0,%esp

which does the same and keeps everything intact.

After some experimenting we found out that this problem is restricted
to gcc4.4.x and to the following -march settings:

i586, pentium, pentium-mmx, k6, k6-2, k6-3, winchip-c6, winchip2, c3,
geode

By adding -mtune=generic the code generator produces always the
expected code.

So forcing -mtune=generic when CONFIG_FUNCTION_GRAPH_TRACER=y is not
pretty, but at the moment the only way to prevent that the kernel
trips over gcc-shrooms induced code madness.

Most distro kernels have CONFIG_X86_GENERIC=y anyway which forces
-mtune=generic as well so it will not impact those.

References: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42109
	    http://lkml.org/lkml/2009/11/19/17Signed-off-by: NThomas Gleixner <tglx@linutronix.de>
LKML-Reference: <alpine.LFD.2.00.0911200206570.24119@localhost.localdomain>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
Cc: Jeff Law <law@redhat.com>
Cc: gcc@gcc.gnu.org
Cc: David Daney <ddaney@caviumnetworks.com>
Cc: Andrew Haley <aph@redhat.com>
Cc: Richard Guenther <richard.guenther@gmail.com>
Cc: stable@kernel.org

Add CPU optimizations for AMD Geode LX.
Signed-off-by: NMatteo Croce <technoboy85@gmail.com>
LKML-Reference: <40101cc30910010811v5d15ff4cx9dd57c9cc9b4b045@mail.gmail.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Add another option when selecting CPU family so the kernel can be
optimized for Intel Atom CPUs. If GCC supports tuning options for
Intel Atom they will be used.
Signed-off-by: NTobias Doerffel <tobias.doerffel@gmail.com>
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>
LKML-Reference: <1251018457-19157-1-git-send-email-tobias.doerffel@gmail.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

The Winchip-2 and Winchip-2A cpu choices select the
same options for kernel and compiler.

Merge them to save few bytes and reduce confusion.
Signed-off-by: NKrzysztof Helt <krzysztof.h1@wp.pl>
Acked-by: NH. Peter Anvin <hpa@zytor.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

binutils, contrary to documented behaviour, will generate long NOPs (a
P6-or-higher instruction which is broken on at least some VIA chips,
Virtual PC/Virtual Server, and some versions of Qemu) depending on the
-mtune= option, which is not supposed to change architectural
behaviour.

Pass an explicit override to the assembler, in case ends up passing
the -mtune= parameter to gas (gcc 4.3.0 does not appear to.)
Signed-off-by: NH. Peter Anvin <hpa@zytor.com>

Moving the ARCH specific Makefiles for i386 and x86_64
required a litle bit tweaking in the top-lvel Makefile.

SRCARCH is now set in the top-level Makefile
because we need this info to include the correct
arch Makefile.
Signed-off-by: NSam Ravnborg <sam@ravnborg.org>

Hi!

I sent this simple patch to lkml about two weeks ago and also cc'ed
to Linus, but seems that the patch got ignored. I decided to write to
you, because you have modified the relevant file most recently.

Below is a copy of the mail that is also available at
<http://lkml.org/lkml/2007/2/28/230>.
Signed-off-by: NAndi Kleen <ak@suse.de>

The VIA C7 is a 686 (with TSC) that supports MMX, SSE and SSE2, it also has
a cache line length of 64 according to
http://www.digit-life.com/articles2/cpu/rmma-via-c7.html.  This patch sets
gcc to -march=686 and select s the correct cache shift.
Signed-off-by: NSimon Arlott <simon@fire.lp0.eu>
Signed-off-by: NAndi Kleen <ak@suse.de>
Cc: Andi Kleen <ak@suse.de>
Cc: Dave Jones <davej@codemonkey.org.uk>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>

gcc doesn't support -mtune=core2 yet, but will be soon. Use -mtune=generic or -mtune=i686
as fallback

TBD need benchmarking for INTEL_USERCOPY etc. So far I used the same defaults as MPENTIUMM
Signed-off-by: NAndi Kleen <ak@suse.de>

The upcomming gcc 4.2 got a new option -mtune=generic to tune
code for both common AMD and Intel CPUs. Use this option
when available for generic kernels.

On x86-64 it is used with CONFIG_GENERIC_CPU. On i386 it is
enabled with CONFIG_X86_GENERIC.  It won't affect the base
line CPU support in any ways and also not the minimum supported CPU.
Signed-off-by: NAndi Kleen <ak@suse.de>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Remove various things which were checking for gcc-1.x and gcc-2.x compilers.

From: Adrian Bunk <bunk@stusta.de>

    Some documentation updates and removes some code paths for gcc < 3.2.
Acked-by: NRussell King <rmk+kernel@arm.linux.org.uk>
Signed-off-by: NAdrian Bunk <bunk@stusta.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

I just noted that -mtune is used, which is only supported on recent GCCs; by
reading http://gcc.gnu.org/gcc-3.4/changes.html, you see "-mcpu has been
renamed to -mtune.", so for GCC < 3.4 we're not using any specific tuning in
the appropriate cases.  However -mcpu is deprecated, so use -mtune when
possible.

This was introduced by commit e9d4dce954a60dc23dd1d967766ca2347b780e54 of the
old tree (between 2.6.10-rc3 and 2.6.10) by Linus Torvalds, to remove the use
of -march, since that could trigger gcc using SSE on its own.  But no
attention was used about using -mcpu vs.  -mtune.

And btw, the old 2.6.4 code (for instance) was:
cflags-$(CONFIG_MPENTIUMII)     += $(call check_gcc,-march=pentium2,-march=i686)
cflags-$(CONFIG_MPENTIUMIII)    += $(call check_gcc,-march=pentium3,-march=i686)
cflags-$(CONFIG_MPENTIUMM)      += $(call check_gcc,-march=pentium3,-march=i686)
cflags-$(CONFIG_MPENTIUM4)      += $(call check_gcc,-march=pentium4,-march=i686)
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

Make UML share the underlying cpu-specific tuning done on i386.

Actually, for now many config options aren't used a lot - but that can be done
later.  Also, UML relies on GCC optimization for things like memcpy and such
more than i386, so specifying the correct -march and -mtune should be enough.
Later, we may want to correct some other stuff.

For instance, since FPU context switching, for us, is done (at least
partially, i.e.  between our kernelspace and userspace) by the host, we may
allow usage of FPU operations by GCC.  This doesn't hold for kernelspace vs.
kernelspace, but we don't support preemption.
Signed-off-by: NPaolo 'Blaisorblade' Giarrusso <blaisorblade@yahoo.it>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>