[PATCH v1 3/6] x86/tdx: Add SetupEventNotifyInterrupt TDX hypercall support

[Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>]

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 guest attestation driver.

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

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 arch/x86/coco/tdx.c | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/arch/x86/coco/tdx.c b/arch/x86/coco/tdx.c
index 2c07f9551d3b..d18508e6150f 100644
--- a/arch/x86/coco/tdx.c
+++ b/arch/x86/coco/tdx.c
@@ -22,6 +22,7 @@
 /* TDX hypercall Leaf IDs */
 #define TDVMCALL_MAP_GPA		0x10001
 #define TDVMCALL_GET_QUOTE		0x10002
+#define TDVMCALL_SETUP_NOTIFY_INTR	0x10004
 
 /* MMIO direction */
 #define EPT_READ	0
@@ -175,6 +176,38 @@ int tdx_hcall_get_quote(void *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.
+ */
+static int tdx_hcall_set_notify_intr(u8 vector)
+{
+	u64 ret;
+
+	/* Minimum vector value allowed is 32 */
+	if (vector < 32)
+		return -EINVAL;
+
+	/*
+	 * Register callback vector address with VMM. More details
+	 * about the ABI can be found in TDX Guest-Host-Communication
+	 * Interface (GHCI), sec titled
+	 * "TDG.VP.VMCALL<SetupEventNotifyInterrupt>".
+	 */
+	ret = _tdx_hypercall(TDVMCALL_SETUP_NOTIFY_INTR, vector, 0, 0, 0);
+
+	if (ret) {
+		if (ret == TDCALL_INVALID_OPERAND)
+			return -EINVAL;
+		return -EIO;
+	}
+
+	return 0;
+}
+
 static void get_info(void)
 {
 	struct tdx_module_output out;
-- 
2.25.1