target/arm/cpu64: max cpu: Introduce sve<N> properties

Introduce cpu properties to give fine control over SVE vector lengths.
We introduce a property for each valid length up to the current
maximum supported, which is 2048-bits. The properties are named, e.g.
sve128, sve256, sve384, sve512, ..., where the number is the number of
bits. See the updates to docs/arm-cpu-features.rst for a description
of the semantics and for example uses.

Note, as sve-max-vq is still present and we'd like to be able to
support qmp_query_cpu_model_expansion with guests launched with e.g.
-cpu max,sve-max-vq=8 on their command lines, then we do allow
sve-max-vq and sve<N> properties to be provided at the same time, but
this is not recommended, and is why sve-max-vq is not mentioned in the
document.  If sve-max-vq is provided then it enables all lengths smaller
than and including the max and disables all lengths larger. It also has
the side-effect that no larger lengths may be enabled and that the max
itself cannot be disabled. Smaller non-power-of-two lengths may,
however, be disabled, e.g. -cpu max,sve-max-vq=4,sve384=off provides a
guest the vector lengths 128, 256, and 512 bits.

This patch has been co-authored with Richard Henderson, who reworked
the target/arm/cpu64.c changes in order to push all the validation and
auto-enabling/disabling steps into the finalizer, resulting in a nice
LOC reduction.

Signed-off-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>
Tested-by: Masayoshi Mizuma <m.mizuma@jp.fujitsu.com>
Reviewed-by: Beata Michalska <beata.michalska@linaro.org>
Message-id: 20191031142734.8590-5-drjones@redhat.com
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 19 insertions, 0 deletions

diff --git a/target/arm/cpu.h b/target/arm/cpu.h
index d844ea21d8..a044d6028b 100644
--- a/target/arm/cpu.h
+++ b/target/arm/cpu.h
@@ -184,8 +184,13 @@ typedef struct {
 
 #ifdef TARGET_AARCH64
 # define ARM_MAX_VQ    16
+void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp);
+uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, uint32_t vq);
 #else
 # define ARM_MAX_VQ    1
+static inline void arm_cpu_sve_finalize(ARMCPU *cpu, Error **errp) { }
+static inline uint32_t arm_cpu_vq_map_next_smaller(ARMCPU *cpu, uint32_t vq)
+{ return 0; }
 #endif
 
 typedef struct ARMVectorReg {
@@ -918,6 +923,18 @@ struct ARMCPU {
 
     /* Used to set the maximum vector length the cpu will support.  */
     uint32_t sve_max_vq;
+
+    /*
+     * 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
+     * length in quadwords.
+     *
+     * While processing properties during initialization, corresponding
+     * sve_vq_init bits are set for bits in sve_vq_map that have been
+     * set by properties.
+     */
+    DECLARE_BITMAP(sve_vq_map, ARM_MAX_VQ);
+    DECLARE_BITMAP(sve_vq_init, ARM_MAX_VQ);
 };
 
 void arm_cpu_post_init(Object *obj);
@@ -1837,6 +1854,8 @@ static inline int arm_feature(CPUARMState *env, int feature)
     return (env->features & (1ULL << feature)) != 0;
 }
 
+void arm_cpu_finalize_features(ARMCPU *cpu, Error **errp);
+
 #if !defined(CONFIG_USER_ONLY)
 /* Return true if exception levels below EL3 are in secure state,
  * or would be following an exception return to that level.