diff mbox series

[03/76] target/arm: arm_reset_sve_state() should set FPSR, not FPCR

Message ID 20250124162836.2332150-4-peter.maydell@linaro.org
State New
Headers show
Series target/arm: Implement FEAT_AFP and FEAT_RPRES | expand

Commit Message

Peter Maydell Jan. 24, 2025, 4:27 p.m. UTC 
The pseudocode ResetSVEState() does:
    FPSR = ZeroExtend(0x0800009f<31:0>, 64);
but QEMU's arm_reset_sve_state() called vfp_set_fpcr() by accident.

Before the advent of FEAT_AFP, this was only setting a collection of
RES0 bits, which vfp_set_fpsr() would then ignore, so the only effect
was that we didn't actually set the FPSR the way we are supposed to
do.  Once FEAT_AFP is implemented, setting the bottom bits of FPSR
will change the floating point behaviour.

Call vfp_set_fpsr(), as we ought to.

(Note for stable backports: commit 7f2a01e7368f9 moved this function
from sme_helper.c to helper.c, but it had the same bug before the
move too.)

Cc: qemu-stable@nongnu.org
Fixes: f84734b87461 ("target/arm: Implement SMSTART, SMSTOP")
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
---
 target/arm/helper.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Richard Henderson Jan. 25, 2025, 3:07 p.m. UTC | #1 
On 1/24/25 08:27, Peter Maydell wrote:
> The pseudocode ResetSVEState() does:
>      FPSR = ZeroExtend(0x0800009f<31:0>, 64);
> but QEMU's arm_reset_sve_state() called vfp_set_fpcr() by accident.
> 
> Before the advent of FEAT_AFP, this was only setting a collection of
> RES0 bits, which vfp_set_fpsr() would then ignore, so the only effect
> was that we didn't actually set the FPSR the way we are supposed to
> do.  Once FEAT_AFP is implemented, setting the bottom bits of FPSR
> will change the floating point behaviour.
> 
> Call vfp_set_fpsr(), as we ought to.
> 
> (Note for stable backports: commit 7f2a01e7368f9 moved this function
> from sme_helper.c to helper.c, but it had the same bug before the
> move too.)
> 
> Cc: qemu-stable@nongnu.org
> Fixes: f84734b87461 ("target/arm: Implement SMSTART, SMSTOP")
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
> ---
>   target/arm/helper.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/target/arm/helper.c b/target/arm/helper.c
> index 63997678513..40bdfc851a5 100644
> --- a/target/arm/helper.c
> +++ b/target/arm/helper.c
> @@ -6413,7 +6413,7 @@ static void arm_reset_sve_state(CPUARMState *env)
>       memset(env->vfp.zregs, 0, sizeof(env->vfp.zregs));
>       /* Recall that FFR is stored as pregs[16]. */
>       memset(env->vfp.pregs, 0, sizeof(env->vfp.pregs));
> -    vfp_set_fpcr(env, 0x0800009f);
> +    vfp_set_fpsr(env, 0x0800009f);
>   }
>   
>   void aarch64_set_svcr(CPUARMState *env, uint64_t new, uint64_t mask)

Oops.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~
diff mbox series

Patch

diff --git a/target/arm/helper.c b/target/arm/helper.c
index 63997678513..40bdfc851a5 100644
--- a/target/arm/helper.c
+++ b/target/arm/helper.c
@@ -6413,7 +6413,7 @@  static void arm_reset_sve_state(CPUARMState *env)
     memset(env->vfp.zregs, 0, sizeof(env->vfp.zregs));
     /* Recall that FFR is stored as pregs[16]. */
     memset(env->vfp.pregs, 0, sizeof(env->vfp.pregs));
-    vfp_set_fpcr(env, 0x0800009f);
+    vfp_set_fpsr(env, 0x0800009f);
 }
 
 void aarch64_set_svcr(CPUARMState *env, uint64_t new, uint64_t mask)