linux-kernel - [PATCH v3 1/4] x86/tdx: Add tdx_mcall

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Date:   Fri, 15 Apr 2022 15:01:06 -0700
From:   Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org,
        Hans de Goede <hdegoede@...hat.com>,
        Mark Gross <mgross@...ux.intel.com>
Cc:     "H . Peter Anvin" <hpa@...or.com>,
        Kuppuswamy Sathyanarayanan 
        <sathyanarayanan.kuppuswamy@...ux.intel.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Andi Kleen <ak@...ux.intel.com>, linux-kernel@...r.kernel.org,
        platform-driver-x86@...r.kernel.org
Subject: [PATCH v3 1/4] x86/tdx: Add tdx_mcall_tdreport() API support

In TDX guest, attestation is mainly used to verify the trustworthiness
of a TD to the 3rd party key servers. First step in attestation process
is to get the TDREPORT data and the generated data is further used in
subsequent steps of the attestation process. TDREPORT data contains
details like TDX module version information, measurement of the TD,
along with a TD-specified nonce

Add a wrapper function (tdx_mcall_tdreport()) to get the TDREPORT from
the TDX Module.

More details about the TDREPORT TDCALL can be found in TDX Guest-Host
Communication Interface (GHCI) for Intel TDX 1.5, section titled
"TDCALL [MR.REPORT]".

Steps involved in attestation process can be found in TDX Guest-Host
Communication Interface (GHCI) for Intel TDX 1.5, section titled
"TD attestation"

This API will be mainly used by the attestation driver. Attestation
driver support will be added by upcoming patches.

Reviewed-by: Tony Luck <tony.luck@...el.com>
Reviewed-by: Andi Kleen <ak@...ux.intel.com>
Acked-by: Kirill A. Shutemov <kirill.shutemov@...ux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
---
 arch/x86/coco/tdx/tdx.c    | 46 ++++++++++++++++++++++++++++++++++++++
 arch/x86/include/asm/tdx.h |  2 ++
 2 files changed, 48 insertions(+)

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index 03deb4d6920d..3e409b618d3f 100644
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -11,10 +11,12 @@
 #include <asm/insn.h>
 #include <asm/insn-eval.h>
 #include <asm/pgtable.h>
+#include <asm/io.h>
 
 /* 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 */
@@ -34,6 +36,10 @@
 #define VE_GET_PORT_NUM(e)	((e) >> 16)
 #define VE_IS_IO_STRING(e)	((e) & BIT(4))
 
+/* TDX Module call error codes */
+#define TDCALL_RETURN_CODE_MASK		0xffffffff00000000
+#define TDCALL_RETURN_CODE(a)		((a) & TDCALL_RETURN_CODE_MASK)
+
 /*
  * Wrapper for standard use of __tdx_hypercall with no output aside from
  * return code.
@@ -98,6 +104,46 @@ 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_tdreport() - Generate TDREPORT_STRUCT using TDCALL.
+ *
+ * @data        : Address of 1024B aligned data to store
+ *                TDREPORT_STRUCT.
+ * @reportdata  : Address of 64B aligned report data
+ *
+ * return 0 on success or failure error number.
+ */
+long tdx_mcall_tdreport(void *data, void *reportdata)
+{
+	u64 ret;
+
+	/*
+	 * Check for a valid TDX guest to ensure this API is only
+	 * used by TDX guest platform. Also make sure "data" and
+	 * "reportdata" pointers are valid.
+	 */
+	if (!data || !reportdata || !cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return -EINVAL;
+
+	/*
+	 * Pass the physical address of user generated reportdata
+	 * and the physical address of out pointer to store the
+	 * TDREPORT data to the TDX module to generate the
+	 * TD report. Generated data contains measurements/configuration
+	 * data of the TD guest. More info about ABI can be found in TDX
+	 * Guest-Host-Communication Interface (GHCI), sec titled
+	 * "TDG.MR.REPORT".
+	 */
+	ret = __tdx_module_call(TDX_GET_REPORT, virt_to_phys(data),
+				virt_to_phys(reportdata), 0, 0, NULL);
+
+	if (ret)
+		return TDCALL_RETURN_CODE(ret);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tdx_mcall_tdreport);
+
 static u64 get_cc_mask(void)
 {
 	struct tdx_module_output out;
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 020c81a7c729..a151f69dd6ef 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -67,6 +67,8 @@ void tdx_safe_halt(void);
 
 bool tdx_early_handle_ve(struct pt_regs *regs);
 
+long tdx_mcall_tdreport(void *data, void *reportdata);
+
 #else
 
 static inline void tdx_early_init(void) { };
-- 
2.25.1