The interaction with the TDX module is like a RPM protocol here. There
are several operations (get tdreport, get quote) that need to input a
blob, and then output another blob. It was considered to use a sysfs
interface for this, but it doesn't fit well into the standard sysfs
model for configuring values. It would be possible to do read/write on
files, but it would need multiple file descriptors, which would be
somewhat messy. ioctls seems to be the best fitting and simplest model
here. There is one ioctl per operation, that takes the input blob and
returns the output blob, and as well as auxiliary ioctls to return the
blob lengths. The ioctls are documented in the header file. 

Reviewed-by: Tony Luck <tony.luck@intel.com>
Reviewed-by: Andi Kleen <redacted>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
---
 drivers/platform/x86/Kconfig            |   9 ++
 drivers/platform/x86/Makefile           |   1 +
 drivers/platform/x86/intel_tdx_attest.c | 171 ++++++++++++++++++++++++
 include/uapi/misc/tdx.h                 |  37 +++++
 4 files changed, 218 insertions(+)
 create mode 100644 drivers/platform/x86/intel_tdx_attest.c
 create mode 100644 include/uapi/misc/tdx.h

diff --git a/drivers/platform/x86/Kconfig b/drivers/platform/x86/Kconfig
index 60592fb88e7a..7d01c473aef6 100644
--- a/drivers/platform/x86/Kconfig
+++ b/drivers/platform/x86/Kconfig

@@ -1301,6 +1301,15 @@ config INTEL_SCU_IPC_UTIL
 	  low level access for debug work and updating the firmware. Say
 	  N unless you will be doing this on an Intel MID platform.
 
+config INTEL_TDX_ATTESTATION
+	tristate "Intel TDX attestation driver"
+	depends on INTEL_TDX_GUEST
+	help
+	  The TDX attestation driver provides IOCTL or MMAP interfaces to
+	  the user to request TDREPORT from the TDX module or request quote
+	  from VMM. It is mainly used to get secure disk decryption keys from
+	  the key server.

+
 config INTEL_TELEMETRY
 	tristate "Intel SoC Telemetry Driver"
 	depends on X86_64

diff --git a/drivers/platform/x86/Makefile b/drivers/platform/x86/Makefile
index dcc8cdb95b4d..83439990ae47 100644
--- a/drivers/platform/x86/Makefile
+++ b/drivers/platform/x86/Makefile

@@ -138,6 +138,7 @@ obj-$(CONFIG_INTEL_SCU_PCI)		+= intel_scu_pcidrv.o
 obj-$(CONFIG_INTEL_SCU_PLATFORM)	+= intel_scu_pltdrv.o
 obj-$(CONFIG_INTEL_SCU_WDT)		+= intel_scu_wdt.o
 obj-$(CONFIG_INTEL_SCU_IPC_UTIL)	+= intel_scu_ipcutil.o
+obj-$(CONFIG_INTEL_TDX_ATTESTATION)	+= intel_tdx_attest.o
 obj-$(CONFIG_INTEL_TELEMETRY)		+= intel_telemetry_core.o \
 					   intel_telemetry_pltdrv.o \
 					   intel_telemetry_debugfs.o

diff --git a/drivers/platform/x86/intel_tdx_attest.c b/drivers/platform/x86/intel_tdx_attest.c
new file mode 100644
index 000000000000..a0225d053851
--- /dev/null
+++ b/drivers/platform/x86/intel_tdx_attest.c

@@ -0,0 +1,171 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * intel_tdx_attest.c - TDX guest attestation interface driver.
+ *
+ * Implements user interface to trigger attestation process and
+ * read the TD Quote result.
+ *
+ * Copyright (C) 2020 Intel Corporation
+ *
+ * Author:
+ *     Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
+ */
+
+#define pr_fmt(fmt) "x86/tdx: attest: " fmt
+
+#include <linux/module.h>
+#include <linux/miscdevice.h>
+#include <linux/uaccess.h>
+#include <linux/fs.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/set_memory.h>
+#include <linux/io.h>
+#include <asm/apic.h>
+#include <asm/tdx.h>
+#include <asm/irq_vectors.h>
+#include <uapi/misc/tdx.h>
+
+#define VERSION				"1.0"
+
+/* Used in Quote memory allocation */
+#define QUOTE_SIZE			(2 * PAGE_SIZE)
+
+/* Mutex to synchronize attestation requests */
+static DEFINE_MUTEX(attestation_lock);
+/* Completion object to track attestation status */
+static DECLARE_COMPLETION(attestation_done);
+
+static void attestation_callback_handler(void)
+{
+	complete(&attestation_done);
+}
+
+static long tdg_attest_ioctl(struct file *file, unsigned int cmd,
+			     unsigned long arg)
+{
+	u64 data = virt_to_phys(file->private_data);