[Qemu-devel] [PATCH 12/13] target/arm/kvm: max cpu: Add support for sve-vls-map

[Andrew Jones <drjones@redhat.com>]

The max cpu type can have its SVE vector lengths explicitly set
with the sve-vls-map property. This patch allows that property
to work when KVM is in use. The map must conform to additional
constraints for KVM which are checked at vcpu init.

Signed-off-by: Andrew Jones <drjones@redhat.com>
---
 target/arm/cpu64.c |  7 +++---
 target/arm/kvm64.c | 56 +++++++++++++++++++++++++++++++++++++++++++---
 2 files changed, 56 insertions(+), 7 deletions(-)

diff --git a/target/arm/cpu64.c b/target/arm/cpu64.c
index 9ac702d54136..94f3dd5b51e5 100644
--- a/target/arm/cpu64.c
+++ b/target/arm/cpu64.c
@@ -310,7 +310,7 @@ static void cpu_set_sve_vls_map(Object *obj, Visitor *v, const char *name,
             error_setg(&err, "SVE vector length map has unsupported lengths");
             error_append_hint(&err, "Valid vector lengths in range [1-%d]\n",
                               ARM_MAX_VQ);
-        } else if (cpu->sve_max_vq != ARM_MAX_VQ &&
+        } else if (cpu->sve_max_vq != ARM_MAX_VQ && cpu->sve_max_vq != -1 &&
                    cpu->sve_max_vq != arm_cpu_fls64(cpu->sve_vls_map)) {
             /*
              * If the user provides both sve-max-vq and sve-vls-map, with
@@ -433,13 +433,12 @@ static void aarch64_max_initfn(Object *obj)
 #endif
 
         cpu->sve_max_vq = ARM_MAX_VQ;
-
-        object_property_add(obj, "sve-vls-map", "uint64", cpu_get_sve_vls_map,
-                            cpu_set_sve_vls_map, NULL, NULL, &error_fatal);
     }
 
     object_property_add(obj, "sve-max-vq", "uint32", cpu_max_get_sve_vq,
                         cpu_max_set_sve_vq, NULL, NULL, &error_fatal);
+    object_property_add(obj, "sve-vls-map", "uint64", cpu_get_sve_vls_map,
+                        cpu_set_sve_vls_map, NULL, NULL, &error_fatal);
 }
 
 struct ARMCPUInfo {
diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
index 11c6334a7c08..5506f019c190 100644
--- a/target/arm/kvm64.c
+++ b/target/arm/kvm64.c
@@ -685,9 +685,9 @@ int kvm_arch_init_vcpu(CPUState *cs)
     } else {
         unset_feature(&env->features, ARM_FEATURE_PMU);
     }
-    if (cpu->sve_max_vq) {
+    if (cpu->sve_max_vq || cpu->sve_vls_map) {
         if (!kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_SVE)) {
-            if (cpu->sve_max_vq == -1) {
+            if (cpu->sve_max_vq == -1 && !cpu->sve_vls_map) {
                 cpu->sve_max_vq = 0;
             } else {
                 error_report("This KVM host does not support SVE");
@@ -704,12 +704,62 @@ int kvm_arch_init_vcpu(CPUState *cs)
         return ret;
     }
 
-    if (cpu->sve_max_vq) {
+    if (cpu->sve_max_vq || cpu->sve_vls_map) {
         uint64_t sve_vls[KVM_ARM64_SVE_VLS_WORDS];
         ret = kvm_arm_get_sve_vls(cs, sve_vls);
         if (ret < 0) {
             return ret;
         }
+        if (cpu->sve_vls_map) {
+            uint64_t ovls;
+            int i;
+
+            /*
+             * We currently only support a single VLS word, as that should
+             * be sufficient for some time (vq=64 means a 8192-bit vector
+             * and KVM currently only supports up to 2048-bit vectors).
+             * The choice to only support a single word for now is due to
+             * the need to input it on the command line. It's much simpler
+             * to input a word as a cpu property than an array of words.
+             * So for now just warn if we detect our assumption was wrong.
+             */
+            for (i = 1; i < KVM_ARM64_SVE_VLS_WORDS; ++i) {
+                if (sve_vls[i]) {
+                    warn_report("KVM supports vector lengths larger than "
+                                "sve-vls-map can select");
+                    sve_vls[i] = 0;
+                }
+            }
+
+            ovls = sve_vls[0];
+            sve_vls[0] = cpu->sve_vls_map;
+
+            if (cpu->sve_vls_map & ~ovls) {
+                error_report("sve-vls-map=0x%lx is not valid on this host "
+                             "which supports 0x%lx", cpu->sve_vls_map, ovls);
+                return -EINVAL;
+            }
+
+            i = arm_cpu_fls64(cpu->sve_vls_map);
+            if (cpu->sve_max_vq && cpu->sve_max_vq != -1 &&
+                cpu->sve_max_vq != i) {
+                error_report("sve-vls-map and sve-max-vq are inconsistent");
+                return -EINVAL;
+            }
+            cpu->sve_max_vq = i;
+
+            /*
+             * sve-vls-map must have all the same vector lengths up to its
+             * max vq that the host supports.
+             */
+            if (cpu->sve_vls_map != (ovls & (BIT_MASK(cpu->sve_max_vq) - 1))) {
+                error_report("sve-vls-map=0x%lx is not valid on this host "
+                             "which supports 0x%lx", cpu->sve_vls_map, ovls);
+                error_printf("All host vector lengths up to %d must also "
+                             "be selected.\n", cpu->sve_max_vq);
+                return -EINVAL;
+            }
+        }
         if (cpu->sve_max_vq == -1) {
             cpu->sve_max_vq = ret;
         } else if (cpu->sve_max_vq > ret) {
-- 
2.20.1