Merge tag 'x86_tdx_for_6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 tdx updates from Dave Hansen:
 "This includes a single chunk of new functionality for TDX guests which
  allows them to talk to the trusted TDX module software and obtain an
  attestation report.

  This report can then be used to prove the trustworthiness of the guest
  to a third party and get access to things like storage encryption
  keys"

* tag 'x86_tdx_for_6.2' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  selftests/tdx: Test TDX attestation GetReport support
  virt: Add TDX guest driver
  x86/tdx: Add a wrapper to get TDREPORT0 from the TDX Module

Author: torvalds

Documentation/virt/coco/tdx-guest.rst

@@ -0,0 +1,52 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+===================================================================
+TDX Guest API Documentation
+===================================================================
+
+1. General description
+======================
+
+The TDX guest driver exposes IOCTL interfaces via the /dev/tdx-guest misc
+device to allow userspace to get certain TDX guest-specific details.
+
+2. API description
+==================
+
+In this section, for each supported IOCTL, the following information is
+provided along with a generic description.
+
+:Input parameters: Parameters passed to the IOCTL and related details.
+:Output: Details about output data and return value (with details about
+         the non common error values).
+
+2.1 TDX_CMD_GET_REPORT0
+-----------------------
+
+:Input parameters: struct tdx_report_req
+:Output: Upon successful execution, TDREPORT data is copied to
+         tdx_report_req.tdreport and return 0. Return -EINVAL for invalid
+         operands, -EIO on TDCALL failure or standard error number on other
+         common failures.
+
+The TDX_CMD_GET_REPORT0 IOCTL can be used by the attestation software to get
+the TDREPORT0 (a.k.a. TDREPORT subtype 0) from the TDX module using
+TDCALL[TDG.MR.REPORT].
+
+A subtype index is added at the end of this IOCTL CMD to uniquely identify the
+subtype-specific TDREPORT request. Although the subtype option is mentioned in
+the TDX Module v1.0 specification, section titled "TDG.MR.REPORT", it is not
+currently used, and it expects this value to be 0. So to keep the IOCTL
+implementation simple, the subtype option was not included as part of the input
+ABI. However, in the future, if the TDX Module supports more than one subtype,
+a new IOCTL CMD will be created to handle it. To keep the IOCTL naming
+consistent, a subtype index is added as part of the IOCTL CMD.
+
+Reference
+---------
+
+TDX reference material is collected here:
+
+https://www.intel.com/content/www/us/en/developer/articles/technical/intel-trust-domain-extensions.html
+
+The driver is based on TDX module specification v1.0 and TDX GHCI specification v1.0.

Documentation/virt/index.rst

@@ -14,6 +14,7 @@ Linux Virtualization Support
    ne_overview
    acrn/index
    coco/sev-guest
+   coco/tdx-guest
    hyperv/index
 
 .. only:: html and subproject

Documentation/x86/tdx.rst

@@ -210,6 +210,49 @@ converted to shared on boot.
 For coherent DMA allocation, the DMA buffer gets converted on the
 allocation. Check force_dma_unencrypted() for details.
 
+Attestation
+===========
+
+Attestation is used to verify the TDX guest trustworthiness to other
+entities before provisioning secrets to the guest. For example, a key
+server may want to use attestation to verify that the guest is the
+desired one before releasing the encryption keys to mount the encrypted
+rootfs or a secondary drive.
+
+The TDX module records the state of the TDX guest in various stages of
+the guest boot process using the build time measurement register (MRTD)
+and runtime measurement registers (RTMR). Measurements related to the
+guest initial configuration and firmware image are recorded in the MRTD
+register. Measurements related to initial state, kernel image, firmware
+image, command line options, initrd, ACPI tables, etc are recorded in
+RTMR registers. For more details, as an example, please refer to TDX
+Virtual Firmware design specification, section titled "TD Measurement".
+At TDX guest runtime, the attestation process is used to attest to these
+measurements.
+
+The attestation process consists of two steps: TDREPORT generation and
+Quote generation.
+
+TDX guest uses TDCALL[TDG.MR.REPORT] to get the TDREPORT (TDREPORT_STRUCT)
+from the TDX module. TDREPORT is a fixed-size data structure generated by
+the TDX module which contains guest-specific information (such as build
+and boot measurements), platform security version, and the MAC to protect
+the integrity of the TDREPORT. A user-provided 64-Byte REPORTDATA is used
+as input and included in the TDREPORT. Typically it can be some nonce
+provided by attestation service so the TDREPORT can be verified uniquely.
+More details about the TDREPORT can be found in Intel TDX Module
+specification, section titled "TDG.MR.REPORT Leaf".
+
+After getting the TDREPORT, the second step of the attestation process
+is to send it to the Quoting Enclave (QE) to generate the Quote. TDREPORT
+by design can only be verified on the local platform as the MAC key is
+bound to the platform. To support remote verification of the TDREPORT,
+TDX leverages Intel SGX Quoting Enclave to verify the TDREPORT locally
+and convert it to a remotely verifiable Quote. Method of sending TDREPORT
+to QE is implementation specific. Attestation software can choose
+whatever communication channel available (i.e. vsock or TCP/IP) to
+send the TDREPORT to QE and receive the Quote.
+
 References
 ==========
 

arch/x86/coco/tdx/tdx.c

@@ -5,6 +5,8 @@
 #define pr_fmt(fmt)     "tdx: " fmt
 
 #include <linux/cpufeature.h>
+#include <linux/export.h>
+#include <linux/io.h>
 #include <asm/coco.h>
 #include <asm/tdx.h>
 #include <asm/vmx.h>
@@ -15,6 +17,7 @@
 /* TDX module Call Leaf IDs */
 #define TDX_GET_INFO			1
 #define TDX_GET_VEINFO			3
+#define TDX_GET_REPORT			4
 #define TDX_ACCEPT_PAGE			6
 
 /* TDX hypercall Leaf IDs */
@@ -36,6 +39,12 @@
 
 #define ATTR_SEPT_VE_DISABLE	BIT(28)
 
+/* TDX Module call error codes */
+#define TDCALL_RETURN_CODE(a)	((a) >> 32)
+#define TDCALL_INVALID_OPERAND	0xc0000100
+
+#define TDREPORT_SUBTYPE_0	0
+
 /*
  * Wrapper for standard use of __tdx_hypercall with no output aside from
  * return code.
@@ -100,6 +109,37 @@ static inline void tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
 		panic("TDCALL %lld failed (Buggy TDX module!)\n", fn);
 }
 
+/**
+ * tdx_mcall_get_report0() - Wrapper to get TDREPORT0 (a.k.a. TDREPORT
+ *                           subtype 0) using TDG.MR.REPORT TDCALL.
+ * @reportdata: Address of the input buffer which contains user-defined
+ *              REPORTDATA to be included into TDREPORT.
+ * @tdreport: Address of the output buffer to store TDREPORT.
+ *
+ * Refer to section titled "TDG.MR.REPORT leaf" in the TDX Module
+ * v1.0 specification for more information on TDG.MR.REPORT TDCALL.
+ * It is used in the TDX guest driver module to get the TDREPORT0.
+ *
+ * Return 0 on success, -EINVAL for invalid operands, or -EIO on
+ * other TDCALL failures.
+ */
+int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
+{
+	u64 ret;
+
+	ret = __tdx_module_call(TDX_GET_REPORT, virt_to_phys(tdreport),
+				virt_to_phys(reportdata), TDREPORT_SUBTYPE_0,
+				0, NULL);
+	if (ret) {
+		if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
+			return -EINVAL;
+		return -EIO;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
+
 static void tdx_parse_tdinfo(u64 *cc_mask)
 {
 	struct tdx_module_output out;

arch/x86/include/asm/tdx.h

@@ -67,6 +67,8 @@ void tdx_safe_halt(void);
 
 bool tdx_early_handle_ve(struct pt_regs *regs);
 
+int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport);
+
 #else
 
 static inline void tdx_early_init(void) { };

drivers/virt/Kconfig

@@ -52,4 +52,6 @@ source "drivers/virt/coco/efi_secret/Kconfig"
 
 source "drivers/virt/coco/sev-guest/Kconfig"
 
+source "drivers/virt/coco/tdx-guest/Kconfig"
+
 endif

drivers/virt/Makefile

@@ -11,3 +11,4 @@ obj-$(CONFIG_NITRO_ENCLAVES)	+= nitro_enclaves/
 obj-$(CONFIG_ACRN_HSM)		+= acrn/
 obj-$(CONFIG_EFI_SECRET)	+= coco/efi_secret/
 obj-$(CONFIG_SEV_GUEST)		+= coco/sev-guest/
+obj-$(CONFIG_INTEL_TDX_GUEST)	+= coco/tdx-guest/

drivers/virt/coco/tdx-guest/Kconfig

@@ -0,0 +1,10 @@
+config TDX_GUEST_DRIVER
+	tristate "TDX Guest driver"
+	depends on INTEL_TDX_GUEST
+	help
+	  The driver provides userspace interface to communicate with
+	  the TDX module to request the TDX guest details like attestation
+	  report.
+
+	  To compile this driver as module, choose M here. The module will
+	  be called tdx-guest.

drivers/virt/coco/tdx-guest/Makefile

@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0
+obj-$(CONFIG_TDX_GUEST_DRIVER) += tdx-guest.o

drivers/virt/coco/tdx-guest/tdx-guest.c

@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TDX guest user interface driver
+ *
+ * Copyright (C) 2022 Intel Corporation
+ */
+
+#include <linux/kernel.h>
+#include <linux/miscdevice.h>
+#include <linux/mm.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/string.h>
+#include <linux/uaccess.h>
+
+#include <uapi/linux/tdx-guest.h>
+
+#include <asm/cpu_device_id.h>
+#include <asm/tdx.h>
+
+static long tdx_get_report0(struct tdx_report_req __user *req)
+{
+	u8 *reportdata, *tdreport;
+	long ret;
+
+	reportdata = kmalloc(TDX_REPORTDATA_LEN, GFP_KERNEL);
+	if (!reportdata)
+		return -ENOMEM;
+
+	tdreport = kzalloc(TDX_REPORT_LEN, GFP_KERNEL);
+	if (!tdreport) {
+		ret = -ENOMEM;
+		goto out;
+	}
+
+	if (copy_from_user(reportdata, req->reportdata, TDX_REPORTDATA_LEN)) {
+		ret = -EFAULT;
+		goto out;
+	}
+
+	/* Generate TDREPORT0 using "TDG.MR.REPORT" TDCALL */
+	ret = tdx_mcall_get_report0(reportdata, tdreport);
+	if (ret)
+		goto out;
+
+	if (copy_to_user(req->tdreport, tdreport, TDX_REPORT_LEN))
+		ret = -EFAULT;
+
+out:
+	kfree(reportdata);
+	kfree(tdreport);
+
+	return ret;
+}
+
+static long tdx_guest_ioctl(struct file *file, unsigned int cmd,
+			    unsigned long arg)
+{
+	switch (cmd) {
+	case TDX_CMD_GET_REPORT0:
+		return tdx_get_report0((struct tdx_report_req __user *)arg);
+	default:
+		return -ENOTTY;
+	}
+}
+
+static const struct file_operations tdx_guest_fops = {
+	.owner = THIS_MODULE,
+	.unlocked_ioctl = tdx_guest_ioctl,
+	.llseek = no_llseek,
+};
+
+static struct miscdevice tdx_misc_dev = {
+	.name = KBUILD_MODNAME,
+	.minor = MISC_DYNAMIC_MINOR,
+	.fops = &tdx_guest_fops,
+};
+
+static const struct x86_cpu_id tdx_guest_ids[] = {
+	X86_MATCH_FEATURE(X86_FEATURE_TDX_GUEST, NULL),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, tdx_guest_ids);
+
+static int __init tdx_guest_init(void)
+{
+	if (!x86_match_cpu(tdx_guest_ids))
+		return -ENODEV;
+
+	return misc_register(&tdx_misc_dev);
+}
+module_init(tdx_guest_init);
+
+static void __exit tdx_guest_exit(void)
+{
+	misc_deregister(&tdx_misc_dev);
+}
+module_exit(tdx_guest_exit);
+
+MODULE_AUTHOR("Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>");
+MODULE_DESCRIPTION("TDX Guest Driver");
+MODULE_LICENSE("GPL");

include/uapi/linux/tdx-guest.h

@@ -0,0 +1,42 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/*
+ * Userspace interface for TDX guest driver
+ *
+ * Copyright (C) 2022 Intel Corporation
+ */
+
+#ifndef _UAPI_LINUX_TDX_GUEST_H_
+#define _UAPI_LINUX_TDX_GUEST_H_
+
+#include <linux/ioctl.h>
+#include <linux/types.h>
+
+/* Length of the REPORTDATA used in TDG.MR.REPORT TDCALL */
+#define TDX_REPORTDATA_LEN              64
+
+/* Length of TDREPORT used in TDG.MR.REPORT TDCALL */
+#define TDX_REPORT_LEN                  1024
+
+/**
+ * struct tdx_report_req - Request struct for TDX_CMD_GET_REPORT0 IOCTL.
+ *
+ * @reportdata: User buffer with REPORTDATA to be included into TDREPORT.
+ *              Typically it can be some nonce provided by attestation
+ *              service, so the generated TDREPORT can be uniquely verified.
+ * @tdreport: User buffer to store TDREPORT output from TDCALL[TDG.MR.REPORT].
+ */
+struct tdx_report_req {
+	__u8 reportdata[TDX_REPORTDATA_LEN];
+	__u8 tdreport[TDX_REPORT_LEN];
+};
+
+/*
+ * TDX_CMD_GET_REPORT0 - Get TDREPORT0 (a.k.a. TDREPORT subtype 0) using
+ *                       TDCALL[TDG.MR.REPORT]
+ *
+ * Return 0 on success, -EIO on TDCALL execution failure, and
+ * standard errno on other general error cases.
+ */
+#define TDX_CMD_GET_REPORT0              _IOWR('T', 1, struct tdx_report_req)
+
+#endif /* _UAPI_LINUX_TDX_GUEST_H_ */

tools/testing/selftests/Makefile

@@ -74,6 +74,7 @@ TARGETS += sync
 TARGETS += syscall_user_dispatch
 TARGETS += sysctl
 TARGETS += tc-testing
+TARGETS += tdx
 TARGETS += timens
 ifneq (1, $(quicktest))
 TARGETS += timers

tools/testing/selftests/tdx/Makefile

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: GPL-2.0
+
+CFLAGS += -O3 -Wl,-no-as-needed -Wall -static
+
+TEST_GEN_PROGS := tdx_guest_test
+
+include ../lib.mk

tools/testing/selftests/tdx/config

@@ -0,0 +1 @@
+CONFIG_TDX_GUEST_DRIVER=y