[PATCH v1 2/6] x86/tdx: Add tdx_hcall_get_quote() API support

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

The second stage in the attestation process is for the guest to request
the VMM generate and sign a quote based on the TDREPORT acquired
earlier. More details about the steps involved in attestation process
can be found in TDX Guest-Host Communication Interface (GHCI) for Intel
TDX 1.5, section titled "TD attestation"

Add tdx_hcall_get_quote() helper function to implement the GetQuote
hypercall.

More details about the GetQuote TDVMCALL are in the Guest-Host
Communication Interface (GHCI) Specification, sec 3.3, titled
"VP.VMCALL<GetQuote>".

This will be used by the TD attestation driver in follow-on patches.

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        | 46 ++++++++++++++++++++++++++++++++++++++
 arch/x86/include/asm/tdx.h |  2 ++
 2 files changed, 48 insertions(+)

diff --git a/arch/x86/coco/tdx.c b/arch/x86/coco/tdx.c
index f01b03e41572..2c07f9551d3b 100644
--- a/arch/x86/coco/tdx.c
+++ b/arch/x86/coco/tdx.c
@@ -21,6 +21,7 @@
 
 /* TDX hypercall Leaf IDs */
 #define TDVMCALL_MAP_GPA		0x10001
+#define TDVMCALL_GET_QUOTE		0x10002
 
 /* MMIO direction */
 #define EPT_READ	0
@@ -38,6 +39,10 @@
 #define TDCALL_INVALID_OPERAND		0x8000000000000000
 #define TDCALL_OPERAND_BUSY		0x8000020000000000
 
+/* TDX hypercall error codes */
+#define TDVMCALL_INVALID_OPERAND	0x8000000000000000
+#define TDVMCALL_GPA_IN_USE		0x8000000000000001
+
 static struct {
 	unsigned int gpa_width;
 	unsigned long attributes;
@@ -129,6 +134,47 @@ int tdx_mcall_tdreport(void *data, void *reportdata)
 }
 EXPORT_SYMBOL_GPL(tdx_mcall_tdreport);
 
+/*
+ * tdx_hcall_get_quote() - Generate TDQUOTE using TDREPORT_STRUCT.
+ *
+ * @data        : Address of 8KB GPA memory which contains
+ *                TDREPORT_STRUCT.
+ *
+ * return 0 on success or failure error number.
+ */
+int tdx_hcall_get_quote(void *data)
+{
+	u64 ret;
+
+	/*
+	 * Use confidential guest TDX check to ensure this API is only
+	 * used by TDX guest platforms.
+	 */
+	if (!data || !cpu_feature_enabled(X86_FEATURE_TDX_GUEST))
+		return -EINVAL;
+
+	/*
+	 * Pass the physical address of tdreport data to the VMM
+	 * and trigger the tdquote generation. Quote data will be
+	 * stored back in the same physical address space. More info
+	 * about ABI can be found in TDX Guest-Host-Communication
+	 * Interface (GHCI), sec titled "TDG.VP.VMCALL<GetQuote>".
+	 */
+	ret = _tdx_hypercall(TDVMCALL_GET_QUOTE, cc_mkdec(virt_to_phys(data)),
+			     0, 0, 0);
+
+	if (ret) {
+		if (ret == TDVMCALL_INVALID_OPERAND)
+			return -EINVAL;
+		else if (ret == TDVMCALL_GPA_IN_USE)
+			return -EBUSY;
+		return -EIO;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(tdx_hcall_get_quote);
+
 static void get_info(void)
 {
 	struct tdx_module_output out;
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index b2e76ae8fdf1..e93ca229d512 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -60,6 +60,8 @@ bool tdx_early_handle_ve(struct pt_regs *regs);
 
 int tdx_mcall_tdreport(void *data, void *reportdata);
 
+int tdx_hcall_get_quote(void *data);
+
 #else
 
 static inline void tdx_early_init(void) { };
-- 
2.25.1