This is a note to let you know that I've just added the patch titled
ARM: vfp: fix saving d16-d31 vfp registers on v6+ kernels
to the 3.6-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
arm-vfp-fix-saving-d16-d31-vfp-registers-on-v6-kernels.patch
and it can be found in the queue-3.6 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 846a136881b8f73c1f74250bf6acfaa309cab1f2 Mon Sep 17 00:00:00 2001
From: Russell King <[email protected]>
Date: Tue, 9 Oct 2012 11:13:26 +0100
Subject: ARM: vfp: fix saving d16-d31 vfp registers on v6+ kernels
From: Russell King <[email protected]>
commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 upstream.
Michael Olbrich reported that his test program fails when built with
-O2 -mcpu=cortex-a8 -mfpu=neon, and a kernel which supports v6 and v7
CPUs:
volatile int x = 2;
volatile int64_t y = 2;
int main() {
volatile int a = 0;
volatile int64_t b = 0;
while (1) {
a = (a + x) % (1 << 30);
b = (b + y) % (1 << 30);
assert(a == b);
}
}
and two instances are run. When built for just v7 CPUs, this program
works fine. It uses the "vadd.i64 d19, d18, d16" VFP instruction.
It appears that we do not save the high-16 double VFP registers across
context switches when the kernel is built for v6 CPUs. Fix that.
Tested-By: Michael Olbrich <[email protected]>
Signed-off-by: Russell King <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
arch/arm/include/asm/vfpmacros.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/arch/arm/include/asm/vfpmacros.h
+++ b/arch/arm/include/asm/vfpmacros.h
@@ -28,7 +28,7 @@
ldr \tmp, =elf_hwcap @ may not have MVFR regs
ldr \tmp, [\tmp, #0]
tst \tmp, #HWCAP_VFPv3D16
- ldceq p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
+ ldceql p11, cr0, [\base],#32*4 @ FLDMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register
space
#else
VFPFMRX \tmp, MVFR0 @ Media and VFP Feature
Register 0
@@ -52,7 +52,7 @@
ldr \tmp, =elf_hwcap @ may not have MVFR regs
ldr \tmp, [\tmp, #0]
tst \tmp, #HWCAP_VFPv3D16
- stceq p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
+ stceql p11, cr0, [\base],#32*4 @ FSTMIAD \base!, {d16-d31}
addne \base, \base, #32*4 @ step over unused register
space
#else
VFPFMRX \tmp, MVFR0 @ Media and VFP Feature
Register 0
Patches currently in stable-queue which might be from
[email protected] are
queue-3.6/arm-vfp-fix-saving-d16-d31-vfp-registers-on-v6-kernels.patch
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