[PATCH v4 4/7] x86/tdx: Add SetupEventNotifyInterrupt TDX hypercall support

[Kuppuswamy Sathyanarayanan]

SetupEventNotifyInterrupt TDX hypercall is used by guest TD to specify
which interrupt vector to use as an event-notify vector to the VMM.
Such registered vector is also used by Host VMM to notify about
completion of GetQuote requests to the Guest TD.

Add tdx_hcall_set_notify_intr() helper function to implement the
SetupEventNotifyInterrupt hypercall.

This will be used by the TD quote driver.

Details about the SetupEventNotifyInterrupt TDVMCALL can be found in
TDX Guest-Host Communication Interface (GHCI) Specification, sec 3.5
"TDG.VP.VMCALL<SetupEventNotifyInterrupt>".

Reviewed-by: Tony Luck <tony.luck@xxxxxxxxx>
Reviewed-by: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@xxxxxxxxxxxxxxx>
---

Change since v3:
 * None

Change since v2:
 * Included TDVMCALL_SUCCESS case check in tdx_hcall_set_notify_intr().

 arch/x86/kernel/tdx.c | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c
index 203ddc4c8412..9fca354e014c 100644
--- a/arch/x86/kernel/tdx.c
+++ b/arch/x86/kernel/tdx.c
@@ -28,6 +28,7 @@
 /* TDX hypercall Leaf IDs */
 #define TDVMCALL_MAP_GPA		0x10001
 #define TDVMCALL_GET_QUOTE		0x10002
+#define TDVMCALL_SETUP_NOTIFY_INTR	0x10004
 
 /* TDX Module call error codes */
 #define TDX_PAGE_ALREADY_ACCEPTED	0x00000b0a00000000
@@ -207,6 +208,32 @@ int tdx_hcall_get_quote(u64 data)
 }
 EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);
 
+/*
+ * tdx_hcall_set_notify_intr() - Setup Event Notify Interrupt Vector.
+ *
+ * @vector        : Vector address to be used for notification.
+ *
+ * return 0 on success or failure error number.
+ */
+int tdx_hcall_set_notify_intr(u8 vector)
+{
+	u64 ret;
+
+	/* Minimum vector value allowed is 32 */
+	if (vector < 32)
+		return -EINVAL;
+
+	ret = _trace_tdx_hypercall(TDVMCALL_SETUP_NOTIFY_INTR, vector, 0, 0, 0,
+				   NULL);
+
+	if (ret == TDVMCALL_SUCCESS)
+		return 0;
+	else if (ret == TDCALL_INVALID_OPERAND)
+		return -EINVAL;
+
+	return -EIO;
+}
+
 static void tdg_get_info(void)
 {
 	u64 ret;
-- 
2.25.1