[Xen-devel] [PATCH v3] x86/altp2m: Add a new hypercall to get the active altp2m index

[Alexandru Stefan ISAILA <aisaila@xxxxxxxxxxxxxxx>]

The patch adds a new lib xc function (xc_altp2m_get_vcpu_p2m_idx) that
uses a new hvmop (HVMOP_altp2m_get_p2m_idx) to get the active altp2m
index from a given vcpu.

Signed-off-by: Alexandru Isaila <aisaila@xxxxxxxxxxxxxxx>

---
Changes since V2:
        - Update comment and title
        - Remove redundant max_vcpu check.
---
 tools/libxc/include/xenctrl.h   |  2 ++
 tools/libxc/xc_altp2m.c         | 25 +++++++++++++++++++++++++
 xen/arch/x86/hvm/hvm.c          | 23 +++++++++++++++++++++++
 xen/include/public/hvm/hvm_op.h |  8 ++++++++
 4 files changed, 58 insertions(+)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 538007a6dc..87526af4b4 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -1942,6 +1942,8 @@ int xc_altp2m_get_mem_access(xc_interface *handle, 
uint32_t domid,
 int xc_altp2m_change_gfn(xc_interface *handle, uint32_t domid,
                          uint16_t view_id, xen_pfn_t old_gfn,
                          xen_pfn_t new_gfn);
+int xc_altp2m_get_vcpu_p2m_idx(xc_interface *handle, uint32_t domid,
+                               uint32_t vcpuid, uint16_t *p2midx);
 
 /** 
  * Mem paging operations.
diff --git a/tools/libxc/xc_altp2m.c b/tools/libxc/xc_altp2m.c
index a86520c232..09dad0355e 100644
--- a/tools/libxc/xc_altp2m.c
+++ b/tools/libxc/xc_altp2m.c
@@ -352,3 +352,28 @@ int xc_altp2m_get_mem_access(xc_interface *handle, 
uint32_t domid,
     xc_hypercall_buffer_free(handle, arg);
     return rc;
 }
+
+int xc_altp2m_get_vcpu_p2m_idx(xc_interface *handle, uint32_t domid,
+                               uint32_t vcpuid, uint16_t *altp2m_idx)
+{
+    int rc;
+
+    DECLARE_HYPERCALL_BUFFER(xen_hvm_altp2m_op_t, arg);
+
+    arg = xc_hypercall_buffer_alloc(handle, arg, sizeof(*arg));
+    if ( arg == NULL )
+        return -1;
+
+    arg->version = HVMOP_ALTP2M_INTERFACE_VERSION;
+    arg->cmd = HVMOP_altp2m_get_p2m_idx;
+    arg->domain = domid;
+    arg->u.get_vcpu_p2m_idx.vcpu_id = vcpuid;
+
+    rc = xencall2(handle->xcall, __HYPERVISOR_hvm_op, HVMOP_altp2m,
+                 HYPERCALL_BUFFER_AS_ARG(arg));
+    if ( !rc )
+        *altp2m_idx = arg->u.get_vcpu_p2m_idx.altp2m_idx;
+
+    xc_hypercall_buffer_free(handle, arg);
+    return rc;
+}
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index 029eea3b85..4ee7e6ce47 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4500,6 +4500,7 @@ static int do_altp2m_op(
     case HVMOP_altp2m_set_mem_access_multi:
     case HVMOP_altp2m_get_mem_access:
     case HVMOP_altp2m_change_gfn:
+    case HVMOP_altp2m_get_p2m_idx:
         break;
 
     default:
@@ -4735,6 +4736,28 @@ static int do_altp2m_op(
                     _gfn(a.u.change_gfn.old_gfn),
                     _gfn(a.u.change_gfn.new_gfn));
         break;
+
+    case HVMOP_altp2m_get_p2m_idx:
+    {
+        struct vcpu *v;
+
+        if ( !altp2m_active(d) )
+        {
+            rc = -EOPNOTSUPP;
+            break;
+        }
+
+        if ( (v = domain_vcpu(d, a.u.get_vcpu_p2m_idx.vcpu_id)) == NULL )
+        {
+            rc = -EINVAL;
+            break;
+        }
+
+        a.u.get_vcpu_p2m_idx.altp2m_idx = altp2m_vcpu_idx(v);
+        rc = __copy_to_guest(arg, &a, 1) ? -EFAULT : 0;
+        break;
+    }
+
     default:
         ASSERT_UNREACHABLE();
     }
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
index c6cd12f596..353f8034d9 100644
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -304,6 +304,11 @@ struct xen_hvm_altp2m_change_gfn {
 typedef struct xen_hvm_altp2m_change_gfn xen_hvm_altp2m_change_gfn_t;
 DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_change_gfn_t);
 
+struct xen_hvm_altp2m_get_vcpu_p2m_idx {
+    uint32_t vcpu_id;
+    uint16_t altp2m_idx;
+};
+
 struct xen_hvm_altp2m_op {
     uint32_t version;   /* HVMOP_ALTP2M_INTERFACE_VERSION */
     uint32_t cmd;
@@ -332,6 +337,8 @@ struct xen_hvm_altp2m_op {
 #define HVMOP_altp2m_get_mem_access       12
 /* Disable altp2m event notifications for a given VCPU */
 #define HVMOP_altp2m_vcpu_disable_notify  13
+/* Get the active vcpu p2m index */
+#define HVMOP_altp2m_get_p2m_idx          14
     domid_t domain;
     uint16_t pad1;
     uint32_t pad2;
@@ -347,6 +354,7 @@ struct xen_hvm_altp2m_op {
         struct xen_hvm_altp2m_set_mem_access_multi set_mem_access_multi;
         struct xen_hvm_altp2m_suppress_ve          suppress_ve;
         struct xen_hvm_altp2m_vcpu_disable_notify  disable_notify;
+        struct xen_hvm_altp2m_get_vcpu_p2m_idx     get_vcpu_p2m_idx;
         uint8_t pad[64];
     } u;
 };
-- 
2.17.1

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