[PATCH v3 16/19] target/riscv/cpu.c: create KVM mock properties

[Daniel Henrique Barboza]

KVM-specific properties are being created inside target/riscv/kvm.c. But
at this moment we're gathering all the remaining properties from TCG and
adding them as is when running KVM. This creates a situation where
non-KVM properties are setting flags to 'true' due to its default
settings (e.g.  Zawrs). Users can also freely enable them via command
line.

This doesn't impact runtime per se because KVM doesn't care about these
flags, but code such as riscv_isa_string_ext() take those flags into
account. The result is that, for a KVM guest, setting non-KVM properties
will make them appear in the riscv,isa DT.

We want to keep the same API for both TCG and KVM and at the same time,
when running KVM, forbid non-KVM extensions to be enabled internally. We
accomplish both by changing riscv_cpu_add_user_properties() to add a
mock/no-op boolean property for every non-KVM extension in
riscv_cpu_extensions[]. Then, when running KVM, users are still free to
set extensions at will, we'll treat non-KVM extensions as a no-op, and
riscv_isa_string_ext() will not report bogus extensions in the DT.

Signed-off-by: Daniel Henrique Barboza <dbarboza@ventanamicro.com>
---
 target/riscv/cpu.c | 36 +++++++++++++++++++++++++++++++++---
 1 file changed, 33 insertions(+), 3 deletions(-)

diff --git a/target/riscv/cpu.c b/target/riscv/cpu.c
index b65db165cc..f5209f0789 100644
--- a/target/riscv/cpu.c
+++ b/target/riscv/cpu.c
@@ -1720,6 +1720,18 @@ static Property riscv_cpu_extensions[] = {
     DEFINE_PROP_END_OF_LIST(),
 };
 
+
+static void cpu_set_cfg_noop(Object *obj, Visitor *v,
+                             const char *name,
+                             void *opaque, Error **errp)
+{
+    bool value;
+
+    if (!visit_type_bool(v, name, &value, errp)) {
+        return;
+    }
+}
+
 /*
  * Add CPU properties with user-facing flags.
  *
@@ -1738,9 +1750,27 @@ static void riscv_cpu_add_user_properties(Object *obj)
     riscv_cpu_add_misa_properties(obj);
 
     for (prop = riscv_cpu_extensions; prop && prop->name; prop++) {
-        /* Check if KVM didn't create the property already */
-        if (object_property_find(obj, prop->name)) {
-            continue;
+        if (riscv_running_kvm()) {
+            /* Check if KVM didn't create the property already */
+            if (object_property_find(obj, prop->name)) {
+                continue;
+            }
+
+            /*
+             * Set every multi-letter extension that KVM doesn't
+             * know as a no-op. This will allow users to set values
+             * to them while keeping their internal state to 'false'.
+             *
+             * We're giving a pass for non-bool properties since they're
+             * not related to the availability of extensions and can be
+             * safely ignored as is.
+             */
+            if (prop->info == &qdev_prop_bool) {
+                object_property_add(obj, prop->name, "bool",
+                                    NULL, cpu_set_cfg_noop,
+                                    NULL, NULL);
+                continue;
+            }
         }
 
         qdev_property_add_static(dev, prop);
-- 
2.41.0