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[v4,11/21] target/arm: default SVE length to 64 bytes for linux-user

Message ID 20191220120438.16114-12-alex.bennee@linaro.org
State New
Headers show
Series gdbstub refactor and SVE support (+check-tcg tweaks) | expand

Commit Message

Alex Bennée Dec. 20, 2019, 12:04 p.m. UTC 
The Linux kernel chooses the default of 64 bytes for SVE registers on
the basis that it is the largest size on known hardware that won't
grow the signal frame. We still honour the sve-max-vq property and
userspace can expand the number of lanes by calling PR_SVE_SET_VL.

This should not make any difference to SVE enabled software as the SVE
is of course vector length agnostic.

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>

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


---
v2
  - tweak zcr_el[1] instead
---
 target/arm/cpu.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

-- 
2.20.1
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Patch

diff --git a/target/arm/cpu.c b/target/arm/cpu.c
index dd51adac059..2d2e786245b 100644
--- a/target/arm/cpu.c
+++ b/target/arm/cpu.c
@@ -199,9 +199,9 @@  static void arm_cpu_reset(CPUState *s)
         /* and to the SVE instructions */
         env->cp15.cpacr_el1 = deposit64(env->cp15.cpacr_el1, 16, 2, 3);
         env->cp15.cptr_el[3] |= CPTR_EZ;
-        /* with maximum vector length */
+        /* with reasonable vector length */
         env->vfp.zcr_el[1] = cpu_isar_feature(aa64_sve, cpu) ?
-                             cpu->sve_max_vq - 1 : 0;
+            MIN(cpu->sve_max_vq - 1, 3) : 0;
         env->vfp.zcr_el[2] = env->vfp.zcr_el[1];
         env->vfp.zcr_el[3] = env->vfp.zcr_el[1];
         /*