Subject: x86/vtx: Allow runtime modification of the exec-sp setting
From: Andrew Cooper <[email-masked]>

See patch for details.

Signed-off-by: Andrew Cooper <[email-masked]>
Reviewed-by: Jan Beulich <[email-masked]>
Reviewed-by: George Dunlap <[email-masked]>

diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index 27050c0877..3c29b7c46f 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -107,6 +107,41 @@ static int __init parse_ept_param(const char *s)
 }
 custom_param("ept", parse_ept_param);
 
+static int parse_ept_param_runtime(const char *s)
+{
+    int val;
+
+    if ( !cpu_has_vmx_ept || !hvm_funcs.hap_supported ||
+         !(hvm_funcs.hap_capabilities &
+           (HVM_HAP_SUPERPAGE_2MB | HVM_HAP_SUPERPAGE_1GB)) )
+    {
+        printk("VMX: EPT not available, or not in use - ignoring\n");
+        return 0;
+    }
+
+    if ( (val = parse_boolean("exec-sp", s, NULL)) < 0 )
+        return -EINVAL;
+
+    if ( val != opt_ept_exec_sp )
+    {
+        struct domain *d;
+
+        opt_ept_exec_sp = val;
+
+        rcu_read_lock(&domlist_read_lock);
+        for_each_domain ( d )
+            if ( paging_mode_hap(d) )
+                p2m_change_entry_type_global(d, p2m_ram_rw, p2m_ram_rw);
+        rcu_read_unlock(&domlist_read_lock);
+    }
+
+    printk("VMX: EPT executable superpages %sabled\n",
+           val ? "en" : "dis");
+
+    return 0;
+}
+custom_runtime_only_param("ept", parse_ept_param_runtime);
+
 /* Dynamic (run-time adjusted) execution control flags. */
 u32 vmx_pin_based_exec_control __read_mostly;
 u32 vmx_cpu_based_exec_control __read_mostly;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 7a52ba993e..416e77b03c 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -263,17 +263,22 @@ int p2m_is_logdirty_range(struct p2m_domain *p2m, unsigned long start,
     return 0;
 }
 
+/*
+ * May be called with ot = nt = p2m_ram_rw for its side effect of
+ * recalculating all PTEs in the p2m.
+ */
 void p2m_change_entry_type_global(struct domain *d,
                                   p2m_type_t ot, p2m_type_t nt)
 {
     struct p2m_domain *p2m = p2m_get_hostp2m(d);
 
-    ASSERT(ot != nt);
     ASSERT(p2m_is_changeable(ot) && p2m_is_changeable(nt));
 
     p2m_lock(p2m);
     p2m->change_entry_type_global(p2m, ot, nt);
-    p2m->global_logdirty = (nt == p2m_ram_logdirty);
+    /* Don't allow 'recalculate' operations to change the logdirty state. */
+    if ( ot != nt )
+        p2m->global_logdirty = (nt == p2m_ram_logdirty);
     p2m_unlock(p2m);
 }