[Xen-devel] [PATCH] x86/altp2m: add altp2m_vcpu_disable_notify

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

Allow altp2m users to disable #VE/VMFUNC alone. Currently it is
only possible to disable this functionality when we disable altp2m
completely; #VE/VMFUNC can only be enabled once per altp2m session.

In addition to making things complete, disabling #VE is also a
workaround for CFW116 ("When Virtualization Exceptions are Enabled,
EPT Violations May Generate Erroneous Virtualization Exceptions")
on Xeon CPUs.

Signed-off-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
---
 tools/libxc/include/xenctrl.h   |  2 ++
 tools/libxc/xc_altp2m.c         | 22 ++++++++++++++++++++++
 xen/arch/x86/hvm/hvm.c          | 31 +++++++++++++++++++++++++++++++
 xen/include/public/hvm/hvm_op.h | 12 +++++++++++-
 4 files changed, 66 insertions(+), 1 deletion(-)

diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index 97ae965..31cdda7 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -1932,6 +1932,8 @@ int xc_altp2m_get_domain_state(xc_interface *handle, 
uint32_t dom, bool *state);
 int xc_altp2m_set_domain_state(xc_interface *handle, uint32_t dom, bool state);
 int xc_altp2m_set_vcpu_enable_notify(xc_interface *handle, uint32_t domid,
                                      uint32_t vcpuid, xen_pfn_t gfn);
+int xc_altp2m_set_vcpu_disable_notify(xc_interface *handle, uint32_t domid,
+                                      uint32_t vcpuid);
 int xc_altp2m_create_view(xc_interface *handle, uint32_t domid,
                           xenmem_access_t default_access, uint16_t *view_id);
 int xc_altp2m_destroy_view(xc_interface *handle, uint32_t domid,
diff --git a/tools/libxc/xc_altp2m.c b/tools/libxc/xc_altp2m.c
index 844b9f1..f8cd603 100644
--- a/tools/libxc/xc_altp2m.c
+++ b/tools/libxc/xc_altp2m.c
@@ -91,6 +91,28 @@ int xc_altp2m_set_vcpu_enable_notify(xc_interface *handle, 
uint32_t domid,
     return rc;
 }
 
+int xc_altp2m_set_vcpu_disable_notify(xc_interface *handle, uint32_t domid,
+                                      uint32_t vcpuid)
+{
+    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_vcpu_disable_notify;
+    arg->domain = domid;
+    arg->u.disable_notify.vcpu_id = vcpuid;
+
+    rc = xencall2(handle->xcall, __HYPERVISOR_hvm_op, HVMOP_altp2m,
+                 HYPERCALL_BUFFER_AS_ARG(arg));
+
+    xc_hypercall_buffer_free(handle, arg);
+    return rc;
+}
+
 int xc_altp2m_create_view(xc_interface *handle, uint32_t domid,
                           xenmem_access_t default_access, uint16_t *view_id)
 {
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index d64b6b6..c1816c5 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -4485,6 +4485,7 @@ static int do_altp2m_op(
     case HVMOP_altp2m_get_domain_state:
     case HVMOP_altp2m_set_domain_state:
     case HVMOP_altp2m_vcpu_enable_notify:
+    case HVMOP_altp2m_vcpu_disable_notify:
     case HVMOP_altp2m_create_p2m:
     case HVMOP_altp2m_destroy_p2m:
     case HVMOP_altp2m_switch_p2m:
@@ -4602,6 +4603,36 @@ static int do_altp2m_op(
         break;
     }
 
+    case HVMOP_altp2m_vcpu_disable_notify:
+    {
+        struct vcpu *v;
+
+        if ( a.u.disable_notify.pad ||
+             a.u.disable_notify.vcpu_id >= d->max_vcpus )
+        {
+            rc = -EINVAL;
+            break;
+        }
+
+        if ( !cpu_has_vmx_virt_exceptions )
+        {
+            rc = -EOPNOTSUPP;
+            break;
+        }
+
+        v = d->vcpu[a.u.enable_notify.vcpu_id];
+
+        if ( gfn_eq(vcpu_altp2m(v).veinfo_gfn, INVALID_GFN) )
+        {
+            rc = -EINVAL;
+            break;
+        }
+
+        vcpu_altp2m(v).veinfo_gfn = INVALID_GFN;
+        altp2m_vcpu_update_vmfunc_ve(v);
+        break;
+    }
+
     case HVMOP_altp2m_create_p2m:
         if ( !(rc = p2m_init_next_altp2m(d, &a.u.view.view)) )
             rc = __copy_to_guest(arg, &a, 1) ? -EFAULT : 0;
diff --git a/xen/include/public/hvm/hvm_op.h b/xen/include/public/hvm/hvm_op.h
index 5878a25..bfc76f5 100644
--- a/xen/include/public/hvm/hvm_op.h
+++ b/xen/include/public/hvm/hvm_op.h
@@ -232,6 +232,13 @@ struct xen_hvm_altp2m_vcpu_enable_notify {
 typedef struct xen_hvm_altp2m_vcpu_enable_notify 
xen_hvm_altp2m_vcpu_enable_notify_t;
 DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_vcpu_enable_notify_t);
 
+struct xen_hvm_altp2m_vcpu_disable_notify {
+    uint32_t vcpu_id;
+    uint32_t pad;
+};
+typedef struct xen_hvm_altp2m_vcpu_disable_notify 
xen_hvm_altp2m_vcpu_disable_notify_t;
+DEFINE_XEN_GUEST_HANDLE(xen_hvm_altp2m_vcpu_disable_notify_t);
+
 struct xen_hvm_altp2m_view {
     /* IN/OUT variable */
     uint16_t view;
@@ -304,7 +311,7 @@ struct xen_hvm_altp2m_op {
 /* Get/set the altp2m state for a domain */
 #define HVMOP_altp2m_get_domain_state     1
 #define HVMOP_altp2m_set_domain_state     2
-/* Set the current VCPU to receive altp2m event notifications */
+/* Set a given VCPU to receive altp2m event notifications */
 #define HVMOP_altp2m_vcpu_enable_notify   3
 /* Create a new view */
 #define HVMOP_altp2m_create_p2m           4
@@ -324,6 +331,8 @@ struct xen_hvm_altp2m_op {
 #define HVMOP_altp2m_get_suppress_ve      11
 /* Get the access of a page of memory from a certain view */
 #define HVMOP_altp2m_get_mem_access       12
+/* Disable altp2m event notifications for a given VCPU */
+#define HVMOP_altp2m_vcpu_disable_notify  13
     domid_t domain;
     uint16_t pad1;
     uint32_t pad2;
@@ -338,6 +347,7 @@ struct xen_hvm_altp2m_op {
         struct xen_hvm_altp2m_change_gfn           change_gfn;
         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;
         uint8_t pad[64];
     } u;
 };
-- 
2.7.4


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