x86/tdx: Add tdx_mcall_extend_rtmr() interface

The TDX guest exposes one MRTD (Build-time Measurement Register) and four
RTMR (Run-time Measurement Register) registers to record the build and boot
measurements of a virtual machine (VM). These registers are similar to PCR
(Platform Configuration Register) registers in the TPM (Trusted Platform
Module) space. This measurement data is used to implement security features
like attestation and trusted boot.

To facilitate updating the RTMR registers, the TDX module provides support
for the `TDG.MR.RTMR.EXTEND` TDCALL which can be used to securely extend
the RTMR registers.

Add helper function to update RTMR registers. It will be used by the TDX
guest driver in enabling RTMR extension support.

Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Cedric Xing <cedric.xing@intel.com>
Acked-by: Dionna Amalie Glaze <dionnaglaze@google.com>
Acked-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20250506-tdx-rtmr-v6-3-ac6ff5e9d58a@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/arch/x86/coco/tdx/tdx.c b/arch/x86/coco/tdx/tdx.c
index edab6d6049bedfb8b7cb2cbb57ab0a670bb6a6c6..0b6804d2a5e14d3ccbee5d19ad8ae6674527fb2f 100644 (file)
--- a/arch/x86/coco/tdx/tdx.c
+++ b/arch/x86/coco/tdx/tdx.c
@@ -36,6 +36,7 @@
 /* TDX Module call error codes */
 #define TDCALL_RETURN_CODE(a)  ((a) >> 32)
 #define TDCALL_INVALID_OPERAND 0xc0000100
+#define TDCALL_OPERAND_BUSY    0x80000200
 
 #define TDREPORT_SUBTYPE_0     0
 
@@ -136,6 +137,42 @@ int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport)
 }
 EXPORT_SYMBOL_GPL(tdx_mcall_get_report0);
 
+/**
+ * tdx_mcall_extend_rtmr() - Wrapper to extend RTMR registers using
+ *                          TDG.MR.RTMR.EXTEND TDCALL.
+ * @index: Index of RTMR register to be extended.
+ * @data: Address of the input buffer with RTMR register extend data.
+ *
+ * Refer to section titled "TDG.MR.RTMR.EXTEND leaf" in the TDX Module v1.0
+ * specification for more information on TDG.MR.RTMR.EXTEND TDCALL.
+ *
+ * It is used in the TDX guest driver module to allow user to extend the RTMR
+ * registers.
+ *
+ * Return 0 on success, -ENXIO for invalid operands, -EBUSY for busy operation,
+ * or -EIO on other TDCALL failures.
+ */
+int tdx_mcall_extend_rtmr(u8 index, u8 *data)
+{
+       struct tdx_module_args args = {
+               .rcx = virt_to_phys(data),
+               .rdx = index,
+       };
+       u64 ret;
+
+       ret = __tdcall(TDG_MR_RTMR_EXTEND, &args);
+       if (ret) {
+               if (TDCALL_RETURN_CODE(ret) == TDCALL_INVALID_OPERAND)
+                       return -ENXIO;
+               if (TDCALL_RETURN_CODE(ret) == TDCALL_OPERAND_BUSY)
+                       return -EBUSY;
+               return -EIO;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(tdx_mcall_extend_rtmr);
+
 /**
  * tdx_hcall_get_quote() - Wrapper to request TD Quote using GetQuote
  *                         hypercall.

diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index a28ff6b141458b57e0bb333646328ea302678d3a..738f583f65cb00a12494b027a5b41347734b044e 100644 (file)
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -13,6 +13,7 @@
 /* TDX module Call Leaf IDs */
 #define TDG_VP_VMCALL                  0
 #define TDG_VP_INFO                    1
+#define TDG_MR_RTMR_EXTEND             2
 #define TDG_VP_VEINFO_GET              3
 #define TDG_MR_REPORT                  4
 #define TDG_MEM_PAGE_ACCEPT            6

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 4a1922ec80cf76ffb9662d0dd34eb02a7c66b4d4..12d17f3ca3016a1bfeb37f07d82721331826fd96 100644 (file)
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -64,6 +64,8 @@ bool tdx_early_handle_ve(struct pt_regs *regs);
 
 int tdx_mcall_get_report0(u8 *reportdata, u8 *tdreport);
 
+int tdx_mcall_extend_rtmr(u8 index, u8 *data);
+
 u64 tdx_hcall_get_quote(u8 *buf, size_t size);
 
 void __init tdx_dump_attributes(u64 td_attr);