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

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

[Andrew Jones]

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@redhat.com>
---

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

[Andrew Jones]

Doh, now I need another change to deal with older compilers

diff --git a/arm/Makefile.arm b/arm/Makefile.arm
index 43b4be1e05eeb..d379a28007493 100644
--- a/arm/Makefile.arm
+++ b/arm/Makefile.arm
@@ -5,7 +5,7 @@
 #
 bits = 32
 ldarch = elf32-littlearm
-machine = -marm
+machine = -marm -mfpu=vfp
 
 # stack.o relies on frame pointers.
 KEEP_FRAME_POINTER := y


I'll send a v2 now.


On Thu, Nov 28, 2019 at 03:34:21PM +0100, Andrew Jones wrote:
> 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@redhat.com>
> ---
> 
> 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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Re: [PATCH kvm-unit-tests] arm: Enable the VFP

[Thomas Huth]

On 28/11/2019 15.34, Andrew Jones wrote:
> 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@redhat.com>
> ---
> 
> 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?

Yes, this patch fixes the problem with GCC9 for me:

 https://gitlab.com/huth/kvm-unit-tests/-/jobs/364079089

Feel free to add my

Tested-by: Thomas Huth <thuth@redhat.com>

and if you like, please also include this hunk:

diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -17,7 +17,7 @@ build-aarch64:

 build-arm:
  script:
- - dnf install -y qemu-system-arm gcc-arm-linux-gnu-8.2.1-1.fc30.2
+ - dnf install -y qemu-system-arm gcc-arm-linux-gnu
  - ./configure --arch=arm --cross-prefix=arm-linux-gnu-
  - make -j2
  - ACCEL=tcg ./run_tests.sh

 Thomas

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