[PATCH v3 27/70] i386/tdx: Add property sept-ve-disable for tdx-guest object

Xiaoyao Li
2023-11-15T07:18:35Z

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>
---
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 8e08257dac2f..3a29659e0155 100644
--- a/qapi/qom.json
+++ b/qapi/qom.json
@@ -883,10 +883,15 @@
#
# 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: 8.2
##
{ 'struct': 'TdxGuestProperties',
- 'data': { }}
+ 'data': { '*sept-ve-disable': 'bool' } }

##
# @ThreadContextProperties:
diff --git a/target/i386/kvm/tdx.c b/target/i386/kvm/tdx.c
index 122a37c93de3..6b9dca03ded5 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] = {
@@ -510,6 +512,24 @@ out:
return r;
}

+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,
@@ -525,6 +545,10 @@ 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