Mirror the behavour of /proc/sys/abi/sve_default_vector_length under the real linux kernel. We have no way of passing along a real default across exec like the kernel can, but this is a decent way of adjusting the startup vector length of a process.
Resolves: https://gitlab.com/qemu-project/qemu/-/issues/482 Signed-off-by: Richard Henderson <richard.hender...@linaro.org> --- target/arm/cpu.h | 5 +++++ target/arm/cpu.c | 14 ++++++++++-- target/arm/cpu64.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 70 insertions(+), 2 deletions(-) diff --git a/target/arm/cpu.h b/target/arm/cpu.h index 52e99344c5..ffd82edaef 100644 --- a/target/arm/cpu.h +++ b/target/arm/cpu.h @@ -1006,6 +1006,11 @@ struct ARMCPU { /* Used to set the maximum vector length the cpu will support. */ uint32_t sve_max_vq; +#ifdef CONFIG_USER_ONLY + /* Used to set the default vector length at process start. */ + uint32_t sve_default_vq; +#endif + /* * In sve_vq_map each set bit is a supported vector length of * (bit-number + 1) * 16 bytes, i.e. each bit number + 1 is the vector diff --git a/target/arm/cpu.c b/target/arm/cpu.c index 9cddfd6a44..b5a2c9eb45 100644 --- a/target/arm/cpu.c +++ b/target/arm/cpu.c @@ -201,7 +201,8 @@ static void arm_cpu_reset(DeviceState *dev) env->cp15.cpacr_el1 = deposit64(env->cp15.cpacr_el1, 16, 2, 3); /* with reasonable vector length */ if (cpu_isar_feature(aa64_sve, cpu)) { - env->vfp.zcr_el[1] = MIN(cpu->sve_max_vq - 1, 3); + env->vfp.zcr_el[1] = + aarch64_sve_zcr_get_valid_len(cpu, cpu->sve_default_vq - 1); } /* * Enable TBI0 but not TBI1. @@ -1051,7 +1052,16 @@ static void arm_cpu_initfn(Object *obj) QLIST_INIT(&cpu->pre_el_change_hooks); QLIST_INIT(&cpu->el_change_hooks); -#ifndef CONFIG_USER_ONLY +#ifdef CONFIG_USER_ONLY +# ifdef TARGET_AARCH64 + /* + * The linux kernel defaults to 512-bit vectors, when sve is supported. + * See documentation for /proc/sys/abi/sve_default_vector_length, and + * our corresponding sve-default-vector-length cpu property. + */ + cpu->sve_default_vq = 4; +# endif +#else /* Our inbound IRQ and FIQ lines */ if (kvm_enabled()) { /* VIRQ and VFIQ are unused with KVM but we add them to maintain diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c index c7a1626bec..0e44a4f154 100644 --- a/target/arm/cpu64.c +++ b/target/arm/cpu64.c @@ -559,6 +559,52 @@ static void cpu_arm_set_sve(Object *obj, bool value, Error **errp) cpu->isar.id_aa64pfr0 = t; } +#ifdef CONFIG_USER_ONLY +/* Mirror linux /proc/sys/abi/sve_default_vector_length. */ +static void cpu_arm_set_sve_default_vec_len(Object *obj, Visitor *v, + const char *name, void *opaque, + Error **errp) +{ + ARMCPU *cpu = ARM_CPU(obj); + uint32_t default_len, default_vq, remainder; + + if (!visit_type_uint32(v, name, &default_len, errp)) { + return; + } + + default_vq = default_len / 128; + remainder = default_len % 128; + + /* + * Note that the 512 max comes from include/uapi/asm/sve_context.h + * and is the maximum architectural width of ZCR_ELx.LEN. + */ + if (remainder || default_vq < 1 || default_vq > 512) { + error_setg(errp, "cannot set sve-default-vector-length"); + if (remainder) { + error_append_hint(errp, "Vector length not a multiple of 128\n"); + } else if (default_vq < 1) { + error_append_hint(errp, "Vector length smaller than 128\n"); + } else { + error_append_hint(errp, "Vector length larger than 65536\n"); + } + return; + } + + cpu->sve_default_vq = default_vq; +} + +static void cpu_arm_get_sve_default_vec_len(Object *obj, Visitor *v, + const char *name, void *opaque, + Error **errp) +{ + ARMCPU *cpu = ARM_CPU(obj); + uint32_t value = cpu->sve_default_vq * 128; + + visit_type_uint32(v, name, &value, errp); +} +#endif + void aarch64_add_sve_properties(Object *obj) { uint32_t vq; @@ -571,6 +617,13 @@ void aarch64_add_sve_properties(Object *obj) object_property_add(obj, name, "bool", cpu_arm_get_sve_vq, cpu_arm_set_sve_vq, NULL, NULL); } + +#ifdef CONFIG_USER_ONLY + /* Mirror linux /proc/sys/abi/sve_default_vector_length. */ + object_property_add(obj, "sve-default-vector-length", "uint32", + cpu_arm_get_sve_default_vec_len, + cpu_arm_set_sve_default_vec_len, NULL, NULL); +#endif } void arm_cpu_pauth_finalize(ARMCPU *cpu, Error **errp) -- 2.25.1
