linux-user/aarch64: Implement PR_SME_GET_VL, PR_SME_SET_VL

These prctl set the Streaming SVE vector length, which may
be completely different from the Normal SVE vector length.

Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
Message-id: 20220708151540.18136-43-richard.henderson@linaro.org
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 54 insertions, 0 deletions

diff --git a/linux-user/aarch64/target_prctl.h b/linux-user/aarch64/target_prctl.h
index 40481e6663..907c314146 100644
--- a/linux-user/aarch64/target_prctl.h
+++ b/linux-user/aarch64/target_prctl.h
@@ -10,6 +10,7 @@ static abi_long do_prctl_sve_get_vl(CPUArchState *env)
 {
     ARMCPU *cpu = env_archcpu(env);
     if (cpu_isar_feature(aa64_sve, cpu)) {
+        /* PSTATE.SM is always unset on syscall entry. */
         return sve_vq(env) * 16;
     }
     return -TARGET_EINVAL;
@@ -27,6 +28,7 @@ static abi_long do_prctl_sve_set_vl(CPUArchState *env, abi_long arg2)
         && arg2 >= 0 && arg2 <= 512 * 16 && !(arg2 & 15)) {
         uint32_t vq, old_vq;
 
+        /* PSTATE.SM is always unset on syscall entry. */
         old_vq = sve_vq(env);
 
         /*
@@ -49,6 +51,58 @@ static abi_long do_prctl_sve_set_vl(CPUArchState *env, abi_long arg2)
 }
 #define do_prctl_sve_set_vl do_prctl_sve_set_vl
 
+static abi_long do_prctl_sme_get_vl(CPUArchState *env)
+{
+    ARMCPU *cpu = env_archcpu(env);
+    if (cpu_isar_feature(aa64_sme, cpu)) {
+        return sme_vq(env) * 16;
+    }
+    return -TARGET_EINVAL;
+}
+#define do_prctl_sme_get_vl do_prctl_sme_get_vl
+
+static abi_long do_prctl_sme_set_vl(CPUArchState *env, abi_long arg2)
+{
+    /*
+     * We cannot support either PR_SME_SET_VL_ONEXEC or PR_SME_VL_INHERIT.
+     * Note the kernel definition of sve_vl_valid allows for VQ=512,
+     * i.e. VL=8192, even though the architectural maximum is VQ=16.
+     */
+    if (cpu_isar_feature(aa64_sme, env_archcpu(env))
+        && arg2 >= 0 && arg2 <= 512 * 16 && !(arg2 & 15)) {
+        int vq, old_vq;
+
+        old_vq = sme_vq(env);
+
+        /*
+         * Bound the value of vq, so that we know that it fits into
+         * the 4-bit field in SMCR_EL1.  Because PSTATE.SM is cleared
+         * on syscall entry, we are not modifying the current SVE
+         * vector length.
+         */
+        vq = MAX(arg2 / 16, 1);
+        vq = MIN(vq, 16);
+        env->vfp.smcr_el[1] =
+            FIELD_DP64(env->vfp.smcr_el[1], SMCR, LEN, vq - 1);
+
+        /* Delay rebuilding hflags until we know if ZA must change. */
+        vq = sve_vqm1_for_el_sm(env, 0, true) + 1;
+
+        if (vq != old_vq) {
+            /*
+             * PSTATE.ZA state is cleared on any change to SVL.
+             * We need not call arm_rebuild_hflags because PSTATE.SM was
+             * cleared on syscall entry, so this hasn't changed VL.
+             */
+            env->svcr = FIELD_DP64(env->svcr, SVCR, ZA, 0);
+            arm_rebuild_hflags(env);
+        }
+        return vq * 16;
+    }
+    return -TARGET_EINVAL;
+}
+#define do_prctl_sme_set_vl do_prctl_sme_set_vl
+
 static abi_long do_prctl_reset_keys(CPUArchState *env, abi_long arg2)
 {
     ARMCPU *cpu = env_archcpu(env);