Patchwork [266/270] ARM: 7566/1: vfp: fix save and restore when running on pre-VFPv3 and CONFIG_VFPv3 set

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Submitter Herton Ronaldo Krzesinski
Date Nov. 26, 2012, 4:59 p.m.
Message ID <1353949160-26803-267-git-send-email-herton.krzesinski@canonical.com>
Download mbox | patch
Permalink /patch/202024/
State New
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Herton Ronaldo Krzesinski - Nov. 26, 2012, 4:59 p.m.
3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Paul Walmsley <paul@pwsan.com>

commit 39141ddfb63a664f26d3f42f64ee386e879b492c upstream.

After commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 ("ARM: vfp: fix
saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board
started crashing during boot with omap2plus_defconfig:

[    3.875122] mmcblk0: mmc0:e624 SD04G 3.69 GiB
[    3.915954]  mmcblk0: p1
[    4.086639] Internal error: Oops - undefined instruction: 0 [#1] SMP ARM
[    4.093719] Modules linked in:
[    4.096954] CPU: 0    Not tainted  (3.6.0-02232-g759e00b #570)
[    4.103149] PC is at vfp_reload_hw+0x1c/0x44
[    4.107666] LR is at __und_usr_fault_32+0x0/0x8

It turns out that the context save/restore fix unmasked a latent bug
in commit 5aaf254409f8d58229107b59507a8235b715a960 ("ARM: 6203/1: Make
VFPv3 usable on ARMv6").  When CONFIG_VFPv3 is set, but the kernel is
booted on a pre-VFPv3 core, the code attempts to save and restore the
d16-d31 VFP registers.  These are only present on non-D16 VFPv3+, so
this results in an undefined instruction exception.  The code didn't
crash before commit 846a136 because the save and restore code was
only touching d0-d15, present on all VFP.

Fix by implementing a request from Russell King to add a new HWCAP
flag that affirmatively indicates the presence of the d16-d31
registers:

   http://marc.info/?l=linux-arm-kernel&m=135013547905283&w=2

and some feedback from Måns to clarify the name of the HWCAP flag.

Signed-off-by: Paul Walmsley <paul@pwsan.com>
Cc: Tony Lindgren <tony@atomide.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Dave Martin <dave.martin@linaro.org>
Cc: Måns Rullgård <mans.rullgard@linaro.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
[ herton: no uapi directory on 3.5 ]
Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
---
 arch/arm/include/asm/hwcap.h     |    3 ++-
 arch/arm/include/asm/vfpmacros.h |   12 ++++++------
 arch/arm/vfp/vfpmodule.c         |    9 ++++++---
 3 files changed, 14 insertions(+), 10 deletions(-)
Ben Hutchings - Dec. 10, 2012, 12:28 a.m.
On Mon, 2012-11-26 at 14:59 -0200, Herton Ronaldo Krzesinski wrote:
> 3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.
> 
> ------------------
> 
> From: Paul Walmsley <paul@pwsan.com>
> 
> commit 39141ddfb63a664f26d3f42f64ee386e879b492c upstream.
> 
> After commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 ("ARM: vfp: fix
> saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board
> started crashing during boot with omap2plus_defconfig:
[...]
> [ herton: no uapi directory on 3.5 ]
> Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
[...]

I've also queued this up for 3.2.  Greg, you'll want to add this to the
other 3.x series since you applied commit 846a136881b8.

Ben.
Greg KH - Dec. 10, 2012, 8:32 p.m.
On Mon, Dec 10, 2012 at 12:28:54AM +0000, Ben Hutchings wrote:
> On Mon, 2012-11-26 at 14:59 -0200, Herton Ronaldo Krzesinski wrote:
> > 3.5.7u1 -stable review patch.  If anyone has any objections, please let me know.
> > 
> > ------------------
> > 
> > From: Paul Walmsley <paul@pwsan.com>
> > 
> > commit 39141ddfb63a664f26d3f42f64ee386e879b492c upstream.
> > 
> > After commit 846a136881b8f73c1f74250bf6acfaa309cab1f2 ("ARM: vfp: fix
> > saving d16-d31 vfp registers on v6+ kernels"), the OMAP 2430SDP board
> > started crashing during boot with omap2plus_defconfig:
> [...]
> > [ herton: no uapi directory on 3.5 ]
> > Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
> [...]
> 
> I've also queued this up for 3.2.  Greg, you'll want to add this to the
> other 3.x series since you applied commit 846a136881b8.

Thanks for letting me know, I've now queued it up after having to fix it
up a bit by hand for the 3.0-stable tree.

greg k-h

Patch

diff --git a/arch/arm/include/asm/hwcap.h b/arch/arm/include/asm/hwcap.h
index 9176261..a2fe893 100644
--- a/arch/arm/include/asm/hwcap.h
+++ b/arch/arm/include/asm/hwcap.h
@@ -18,11 +18,12 @@ 
 #define HWCAP_THUMBEE	(1 << 11)
 #define HWCAP_NEON	(1 << 12)
 #define HWCAP_VFPv3	(1 << 13)
-#define HWCAP_VFPv3D16	(1 << 14)
+#define HWCAP_VFPv3D16	(1 << 14)	/* also set for VFPv4-D16 */
 #define HWCAP_TLS	(1 << 15)
 #define HWCAP_VFPv4	(1 << 16)
 #define HWCAP_IDIVA	(1 << 17)
 #define HWCAP_IDIVT	(1 << 18)
+#define HWCAP_VFPD32	(1 << 19)	/* set if VFP has 32 regs (not 16) */
 #define HWCAP_IDIV	(HWCAP_IDIVA | HWCAP_IDIVT)
 
 #if defined(__KERNEL__)
diff --git a/arch/arm/include/asm/vfpmacros.h b/arch/arm/include/asm/vfpmacros.h
index bf53047..c49c8f7 100644
--- a/arch/arm/include/asm/vfpmacros.h
+++ b/arch/arm/include/asm/vfpmacros.h
@@ -27,9 +27,9 @@ 
 #if __LINUX_ARM_ARCH__ <= 6
 	ldr	\tmp, =elf_hwcap		    @ may not have MVFR regs
 	ldr	\tmp, [\tmp, #0]
-	tst	\tmp, #HWCAP_VFPv3D16
-	ldceql	p11, cr0, [\base],#32*4		    @ FLDMIAD \base!, {d16-d31}
-	addne	\base, \base, #32*4		    @ step over unused register space
+	tst	\tmp, #HWCAP_VFPD32
+	ldcnel	p11, cr0, [\base],#32*4		    @ FLDMIAD \base!, {d16-d31}
+	addeq	\base, \base, #32*4		    @ step over unused register space
 #else
 	VFPFMRX	\tmp, MVFR0			    @ Media and VFP Feature Register 0
 	and	\tmp, \tmp, #MVFR0_A_SIMD_MASK	    @ A_SIMD field
@@ -51,9 +51,9 @@ 
 #if __LINUX_ARM_ARCH__ <= 6
 	ldr	\tmp, =elf_hwcap		    @ may not have MVFR regs
 	ldr	\tmp, [\tmp, #0]
-	tst	\tmp, #HWCAP_VFPv3D16
-	stceql	p11, cr0, [\base],#32*4		    @ FSTMIAD \base!, {d16-d31}
-	addne	\base, \base, #32*4		    @ step over unused register space
+	tst	\tmp, #HWCAP_VFPD32
+	stcnel	p11, cr0, [\base],#32*4		    @ FSTMIAD \base!, {d16-d31}
+	addeq	\base, \base, #32*4		    @ step over unused register space
 #else
 	VFPFMRX	\tmp, MVFR0			    @ Media and VFP Feature Register 0
 	and	\tmp, \tmp, #MVFR0_A_SIMD_MASK	    @ A_SIMD field
diff --git a/arch/arm/vfp/vfpmodule.c b/arch/arm/vfp/vfpmodule.c
index c834b32..3b44e0d 100644
--- a/arch/arm/vfp/vfpmodule.c
+++ b/arch/arm/vfp/vfpmodule.c
@@ -701,11 +701,14 @@  static int __init vfp_init(void)
 			elf_hwcap |= HWCAP_VFPv3;
 
 			/*
-			 * Check for VFPv3 D16. CPUs in this configuration
-			 * only have 16 x 64bit registers.
+			 * Check for VFPv3 D16 and VFPv4 D16.  CPUs in
+			 * this configuration only have 16 x 64bit
+			 * registers.
 			 */
 			if (((fmrx(MVFR0) & MVFR0_A_SIMD_MASK)) == 1)
-				elf_hwcap |= HWCAP_VFPv3D16;
+				elf_hwcap |= HWCAP_VFPv3D16; /* also v4-D16 */
+			else
+				elf_hwcap |= HWCAP_VFPD32;
 		}
 #endif
 		/*