[Xen-devel] [PATCH] x86/altp2m: Allow setting the #VE info page for an arbitrary VCPU

[Adrian Pop <apop@xxxxxxxxxxxxxxx>]

The intended use-case of this patch is to allow either Dom0 or a control
domain to activate #VE for an introspected guest, and not having to do
this necessarily from an in-guest agent.

Signed-off-by: Adrian Pop <apop@xxxxxxxxxxxxxxx>
---
 tools/libxc/xc_altp2m.c |  1 -
 xen/arch/x86/hvm/hvm.c  | 47 +++++++++++++++++++++++++++++++++--------
 2 files changed, 38 insertions(+), 10 deletions(-)

diff --git a/tools/libxc/xc_altp2m.c b/tools/libxc/xc_altp2m.c
index 1c9b572e2b..be5bfd28ed 100644
--- a/tools/libxc/xc_altp2m.c
+++ b/tools/libxc/xc_altp2m.c
@@ -68,7 +68,6 @@ int xc_altp2m_set_domain_state(xc_interface *handle, uint32_t 
dom, bool state)
     return rc;
 }
 
-/* This is a bit odd to me that it acts on current.. */
 int xc_altp2m_set_vcpu_enable_notify(xc_interface *handle, uint32_t domid,
                                      uint32_t vcpuid, xen_pfn_t gfn)
 {
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 4e318cede4..0157611384 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4467,6 +4467,30 @@ static int hvmop_get_param(
     return rc;
 }
 
+/*
+ * Find the struct vcpu given a dom_id and vcpu_id.
+ * Return NULL if not found.
+ */
+static struct vcpu *__get_vcpu(domid_t domain_id, uint32_t vcpu_id)
+{
+    struct domain *dom;
+    struct vcpu *v;
+
+    dom = rcu_lock_domain_by_id(domain_id);
+
+    for_each_vcpu( dom, v )
+    {
+        if ( vcpu_id == v->vcpu_id )
+        {
+            rcu_unlock_domain(dom);
+            return v;
+        }
+    }
+
+    rcu_unlock_domain(dom);
+    return NULL;
+}
+
 static int do_altp2m_op(
     XEN_GUEST_HANDLE_PARAM(void) arg)
 {
@@ -4504,8 +4528,7 @@ static int do_altp2m_op(
         return -EOPNOTSUPP;
     }
 
-    d = ( a.cmd != HVMOP_altp2m_vcpu_enable_notify ) ?
-        rcu_lock_domain_by_any_id(a.domain) : rcu_lock_current_domain();
+    d = rcu_lock_domain_by_any_id(a.domain);
 
     if ( d == NULL )
         return -ESRCH;
@@ -4576,26 +4599,32 @@ static int do_altp2m_op(
 
     case HVMOP_altp2m_vcpu_enable_notify:
     {
-        struct vcpu *curr = current;
+        struct vcpu *v;
         p2m_type_t p2mt;
 
-        if ( a.u.enable_notify.pad || a.domain != DOMID_SELF ||
-             a.u.enable_notify.vcpu_id != curr->vcpu_id )
+        if ( a.u.enable_notify.pad )
         {
             rc = -EINVAL;
             break;
         }
 
-        if ( !gfn_eq(vcpu_altp2m(curr).veinfo_gfn, INVALID_GFN) ||
-             mfn_eq(get_gfn_query_unlocked(curr->domain,
+        v = __get_vcpu(a.domain, a.u.enable_notify.vcpu_id);
+        if ( !v )
+        {
+            rc = -EFAULT;
+            break;
+        }
+
+        if ( !gfn_eq(vcpu_altp2m(v).veinfo_gfn, INVALID_GFN) ||
+             mfn_eq(get_gfn_query_unlocked(v->domain,
                     a.u.enable_notify.gfn, &p2mt), INVALID_MFN) )
         {
             rc = -EINVAL;
             break;
         }
 
-        vcpu_altp2m(curr).veinfo_gfn = _gfn(a.u.enable_notify.gfn);
-        altp2m_vcpu_update_vmfunc_ve(curr);
+        vcpu_altp2m(v).veinfo_gfn = _gfn(a.u.enable_notify.gfn);
+        altp2m_vcpu_update_vmfunc_ve(v);
         break;
     }
 
-- 
2.17.0


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel