[RFC 4/6] capabilities: introduce console io as a domain capability

["Daniel P. Smith" <dpsmith@xxxxxxxxxxxxxxxxxxxx>]

The field `is_console` suggests that the field represents a state of being or
posession, not that it reflects the privilege to access the console. In this
patch the field is renamed to capabilities to encapsulate the capabilities a
domain has been granted. The first capability being the ability to read/write
the Xen console.

Signed-off-by: Daniel P. Smith <dpsmith@xxxxxxxxxxxxxxxxxxxx>
---
 xen/arch/arm/domain_build.c |  4 +++-
 xen/include/xen/sched.h     | 25 +++++++++++++++++++++++--
 xen/include/xsm/dummy.h     |  2 +-
 3 files changed, 27 insertions(+), 4 deletions(-)

diff --git a/xen/arch/arm/domain_build.c b/xen/arch/arm/domain_build.c
index 51b4daefe1..ad7432b029 100644
--- a/xen/arch/arm/domain_build.c
+++ b/xen/arch/arm/domain_build.c
@@ -4076,7 +4076,9 @@ void __init create_domUs(void)
             panic("Error creating domain %s (rc = %ld)\n",
                   dt_node_name(node), PTR_ERR(d));
 
-        d->is_console = true;
+        if ( ! domain_set_cap(d, CAP_CONSOLE_IO) )
+            printk("failed setting console_io on %pd\n", d);
+
         dt_device_set_used_by(node, d->domain_id);
 
         rc = construct_domU(d, node);
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index ec0f9baff6..b04fbe0565 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -472,8 +472,8 @@ struct domain
 #define ROLE_HARDWARE_DOMAIN   (1U<<2)
 #define ROLE_XENSTORE_DOMAIN   (1U<<3)
     uint8_t          role;
-    /* Can this guest access the Xen console? */
-    bool             is_console;
+#define CAP_CONSOLE_IO  (1U<<0)
+    uint8_t          capabilities;
     /* Is this guest being debugged by dom0? */
     bool             debugger_attached;
     /*
@@ -1146,6 +1146,27 @@ static always_inline bool is_hvm_vcpu(const struct vcpu 
*v)
     return is_hvm_domain(v->domain);
 }
 
+static always_inline bool domain_has_cap(
+    const struct domain *d, uint8_t cap)
+{
+    return d->capabilities & cap;
+}
+
+static always_inline bool domain_set_cap(
+    struct domain *d, uint8_t cap)
+{
+    switch ( cap )
+    {
+    case CAP_CONSOLE_IO:
+        d->capabilities |= cap;
+        break;
+    default:
+        return false;
+    }
+
+    return domain_has_cap(d, cap);
+}
+
 static always_inline bool hap_enabled(const struct domain *d)
 {
     /* sanitise_domain_config() rejects HAP && !HVM */
diff --git a/xen/include/xsm/dummy.h b/xen/include/xsm/dummy.h
index 18f1ddd127..067ff1d111 100644
--- a/xen/include/xsm/dummy.h
+++ b/xen/include/xsm/dummy.h
@@ -268,7 +268,7 @@ static XSM_INLINE int cf_check xsm_console_io(
     XSM_DEFAULT_ARG struct domain *d, int cmd)
 {
     XSM_ASSERT_ACTION(XSM_OTHER);
-    if ( d->is_console )
+    if ( domain_has_cap(d, CAP_CONSOLE_IO) )
         return xsm_default_action(XSM_HOOK, d, NULL);
 #ifdef CONFIG_VERBOSE_DEBUG
     if ( cmd == CONSOLEIO_write )
-- 
2.20.1