Bit 28 of TD attribute, named SEPT_VE_DISABLE. When set to 1, it disables
EPT violation conversion to #VE on guest TD access of PENDING pages.

Some guest OS (e.g., Linux TD guest) may require this bit as 1.
Otherwise refuse to boot.

Add sept-ve-disable property for tdx-guest object, for user to configure
this bit.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
---
Changes in v4:
- collect Acked-by from Markus

Changes in v3:
- update the comment of property @sept-ve-disable to make it more
  descriptive and use new format. (Daniel and Markus)
---
 qapi/qom.json         |  7 ++++++-
 target/i386/kvm/tdx.c | 24 ++++++++++++++++++++++++
 2 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/qapi/qom.json b/qapi/qom.json
index 5b3c3146947f..2177f3101382 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -900,10 +900,15 @@
 #
 # Properties for tdx-guest objects.
 #
+# @sept-ve-disable: toggle bit 28 of TD attributes to control disabling
+#     of EPT violation conversion to #VE on guest TD access of PENDING
+#     pages.  Some guest OS (e.g., Linux TD guest) may require this to
+#     be set, otherwise they refuse to boot.
+#
 # Since: 9.0
 ##
 { 'struct': 'TdxGuestProperties',
-  'data': { }}
+  'data': { '*sept-ve-disable': 'bool' } }
 
 ##
 # @ThreadContextProperties:
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 634aca504b32..51db64bec7ce 100644
--- a/target/i386/kvm/tdx.c
+++ b/target/i386/kvm/tdx.c
@@ -32,6 +32,8 @@
                                      (1U << KVM_FEATURE_PV_SCHED_YIELD) | \
                                      (1U << KVM_FEATURE_MSI_EXT_DEST_ID))
 
+#define TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE   BIT_ULL(28)
+
 #define TDX_ATTRIBUTES_MAX_BITS      64
 
 static FeatureMask tdx_attrs_ctrl_fields[TDX_ATTRIBUTES_MAX_BITS] = {
@@ -513,6 +515,24 @@ int tdx_pre_create_vcpu(CPUState *cpu, Error **errp)
     return 0;
 }
 
+static bool tdx_guest_get_sept_ve_disable(Object *obj, Error **errp)
+{
+    TdxGuest *tdx = TDX_GUEST(obj);
+
+    return !!(tdx->attributes & TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE);
+}
+
+static void tdx_guest_set_sept_ve_disable(Object *obj, bool value, Error **errp)
+{
+    TdxGuest *tdx = TDX_GUEST(obj);
+
+    if (value) {
+        tdx->attributes |= TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE;
+    } else {
+        tdx->attributes &= ~TDX_TD_ATTRIBUTES_SEPT_VE_DISABLE;
+    }
+}
+
 /* tdx guest */
 OBJECT_DEFINE_TYPE_WITH_INTERFACES(TdxGuest,
                                    tdx_guest,
@@ -528,6 +548,10 @@ static void tdx_guest_init(Object *obj)
     qemu_mutex_init(&tdx->lock);
 
     tdx->attributes = 0;
+
+    object_property_add_bool(obj, "sept-ve-disable",
+                             tdx_guest_get_sept_ve_disable,
+                             tdx_guest_set_sept_ve_disable);
 }
 
 static void tdx_guest_finalize(Object *obj)
-- 
2.34.1