[PATCH kvm-unit-tests] arm: Enable the VFP

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Variable argument macros frequently depend on floating point
registers. Indeed we needed to enable the VFP for arm64 since its
introduction in order to use printf and the like. Somehow we
didn't need to do that for arm32 until recently when compiling
with GCC 9.

Signed-off-by: Andrew Jones <drjones@xxxxxxxxxx>
---

CC'ing Thomas because I think he had to workaround travis tests
failing due to this issue once. Maybe travis can now be
un-worked-around?


 arm/cstart.S | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/arm/cstart.S b/arm/cstart.S
index 114726feab82..bc6219d8a3ee 100644
--- a/arm/cstart.S
+++ b/arm/cstart.S
@@ -50,10 +50,11 @@ start:
 	mov	r0, r2
 	push	{r0-r1}
 
-	/* set up vector table and mode stacks */
+	/* set up vector table, mode stacks, and enable the VFP */
 	mov	r0, lr			@ lr is stack top (see above),
 					@ which is the exception stacks base
 	bl	exceptions_init
+	bl	enable_vfp
 
 	/* complete setup */
 	pop	{r0-r1}
@@ -100,6 +101,16 @@ exceptions_init:
 	isb
 	mov	pc, lr
 
+enable_vfp:
+	/* Enable full access to CP10 and CP11: */
+	mov	r0, #(3 << 22 | 3 << 20)
+	mcr	p15, 0, r0, c1, c0, 2
+	isb
+	/* Set the FPEXC.EN bit to enable Advanced SIMD and VFP: */
+	mov	r0, #(1 << 30)
+	vmsr	fpexc, r0
+	mov	pc, lr
+
 .text
 
 .global get_mmu_off
@@ -130,6 +141,7 @@ secondary_entry:
 	ldr	r0, [r1]
 	mov	sp, r0
 	bl	exceptions_init
+	bl	enable_vfp
 
 	/* finish init in C code */
 	bl	secondary_cinit
-- 
2.21.0





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