--- /dev/null
+/* SPDX-License-Identifier: GPL-2.0 */
+#include <asm/asm-offsets.h>
+#include <asm/asm.h>
+#include <asm/frame.h>
+#include <asm/unwind_hints.h>
+
+#include <linux/linkage.h>
+#include <linux/bits.h>
+#include <linux/errno.h>
+
+#include "../../virt/vmx/tdx/tdxcall.S"
+
+/*
+ * Bitmasks of exposed registers (with VMM).
+ */
+#define TDX_R10 BIT(10)
+#define TDX_R11 BIT(11)
+#define TDX_R12 BIT(12)
+#define TDX_R13 BIT(13)
+#define TDX_R14 BIT(14)
+#define TDX_R15 BIT(15)
+
+/*
+ * These registers are clobbered to hold arguments for each
+ * TDVMCALL. They are safe to expose to the VMM.
+ * Each bit in this mask represents a register ID. Bit field
+ * details can be found in TDX GHCI specification, section
+ * titled "TDCALL [TDG.VP.VMCALL] leaf".
+ */
+#define TDVMCALL_EXPOSE_REGS_MASK ( TDX_R10 | TDX_R11 | \
+ TDX_R12 | TDX_R13 | \
+ TDX_R14 | TDX_R15 )
+
+/*
+ * __tdx_module_call() - Used by TDX guests to request services from
+ * the TDX module (does not include VMM services) using TDCALL instruction.
+ *
+ * Transforms function call register arguments into the TDCALL register ABI.
+ * After TDCALL operation, TDX module output is saved in @out (if it is
+ * provided by the user).
+ *
+ *-------------------------------------------------------------------------
+ * TDCALL ABI:
+ *-------------------------------------------------------------------------
+ * Input Registers:
+ *
+ * RAX - TDCALL Leaf number.
+ * RCX,RDX,R8-R9 - TDCALL Leaf specific input registers.
+ *
+ * Output Registers:
+ *
+ * RAX - TDCALL instruction error code.
+ * RCX,RDX,R8-R11 - TDCALL Leaf specific output registers.
+ *
+ *-------------------------------------------------------------------------
+ *
+ * __tdx_module_call() function ABI:
+ *
+ * @fn (RDI) - TDCALL Leaf ID, moved to RAX
+ * @rcx (RSI) - Input parameter 1, moved to RCX
+ * @rdx (RDX) - Input parameter 2, moved to RDX
+ * @r8 (RCX) - Input parameter 3, moved to R8
+ * @r9 (R8) - Input parameter 4, moved to R9
+ *
+ * @out (R9) - struct tdx_module_output pointer
+ * stored temporarily in R12 (not
+ * shared with the TDX module). It
+ * can be NULL.
+ *
+ * Return status of TDCALL via RAX.
+ */
+SYM_FUNC_START(__tdx_module_call)
+ FRAME_BEGIN
+ TDX_MODULE_CALL host=0
+ FRAME_END
+ ret
+SYM_FUNC_END(__tdx_module_call)
+
+/*
+ * __tdx_hypercall() - Make hypercalls to a TDX VMM using TDVMCALL leaf
+ * of TDCALL instruction
+ *
+ * Transforms values in function call argument struct tdx_hypercall_args @args
+ * into the TDCALL register ABI. After TDCALL operation, VMM output is saved
+ * back in @args.
+ *
+ *-------------------------------------------------------------------------
+ * TD VMCALL ABI:
+ *-------------------------------------------------------------------------
+ *
+ * Input Registers:
+ *
+ * RAX - TDCALL instruction leaf number (0 - TDG.VP.VMCALL)
+ * RCX - BITMAP which controls which part of TD Guest GPR
+ * is passed as-is to the VMM and back.
+ * R10 - Set 0 to indicate TDCALL follows standard TDX ABI
+ * specification. Non zero value indicates vendor
+ * specific ABI.
+ * R11 - VMCALL sub function number
+ * RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific arguments.
+ * R8-R9, R12-R15 - Same as above.
+ *
+ * Output Registers:
+ *
+ * RAX - TDCALL instruction status (Not related to hypercall
+ * output).
+ * R10 - Hypercall output error code.
+ * R11-R15 - Hypercall sub function specific output values.
+ *
+ *-------------------------------------------------------------------------
+ *
+ * __tdx_hypercall() function ABI:
+ *
+ * @args (RDI) - struct tdx_hypercall_args for input and output
+ * @flags (RSI) - TDX_HCALL_* flags
+ *
+ * On successful completion, return the hypercall error code.
+ */
+SYM_FUNC_START(__tdx_hypercall)
+ FRAME_BEGIN
+
+ /* Save callee-saved GPRs as mandated by the x86_64 ABI */
+ push %r15
+ push %r14
+ push %r13
+ push %r12
+
+ /* Mangle function call ABI into TDCALL ABI: */
+ /* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */
+ xor %eax, %eax
+
+ /* Copy hypercall registers from arg struct: */
+ movq TDX_HYPERCALL_r10(%rdi), %r10
+ movq TDX_HYPERCALL_r11(%rdi), %r11
+ movq TDX_HYPERCALL_r12(%rdi), %r12
+ movq TDX_HYPERCALL_r13(%rdi), %r13
+ movq TDX_HYPERCALL_r14(%rdi), %r14
+ movq TDX_HYPERCALL_r15(%rdi), %r15
+
+ movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx
+
+ tdcall
+
+ /*
+ * RAX==0 indicates a failure of the TDVMCALL mechanism itself and that
+ * something has gone horribly wrong with the TDX module.
+ *
+ * The return status of the hypercall operation is in a separate
+ * register (in R10). Hypercall errors are a part of normal operation
+ * and are handled by callers.
+ */
+ testq %rax, %rax
+ jne .Lpanic
+
+ /* TDVMCALL leaf return code is in R10 */
+ movq %r10, %rax
+
+ /* Copy hypercall result registers to arg struct if needed */
+ testq $TDX_HCALL_HAS_OUTPUT, %rsi
+ jz .Lout
+
+ movq %r10, TDX_HYPERCALL_r10(%rdi)
+ movq %r11, TDX_HYPERCALL_r11(%rdi)
+ movq %r12, TDX_HYPERCALL_r12(%rdi)
+ movq %r13, TDX_HYPERCALL_r13(%rdi)
+ movq %r14, TDX_HYPERCALL_r14(%rdi)
+ movq %r15, TDX_HYPERCALL_r15(%rdi)
+.Lout:
+ /*
+ * Zero out registers exposed to the VMM to avoid speculative execution
+ * with VMM-controlled values. This needs to include all registers
+ * present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15
+ * context will be restored.
+ */
+ xor %r10d, %r10d
+ xor %r11d, %r11d
+
+ /* Restore callee-saved GPRs as mandated by the x86_64 ABI */
+ pop %r12
+ pop %r13
+ pop %r14
+ pop %r15
+
+ FRAME_END
+
+ retq
+.Lpanic:
+ call __tdx_hypercall_failed
+ /* __tdx_hypercall_failed never returns */
+ jmp .Lpanic
+SYM_FUNC_END(__tdx_hypercall)
#ifndef _ASM_X86_TDX_H
#define _ASM_X86_TDX_H
+#include <linux/bits.h>
#include <linux/init.h>
#include <linux/bits.h>
#define TDX_CPUID_LEAF_ID 0x21
#define TDX_IDENT "IntelTDX "
+#define TDX_HYPERCALL_STANDARD 0
+
+#define TDX_HCALL_HAS_OUTPUT BIT(0)
+
/*
* SW-defined error codes.
*
u64 r11;
};
+/*
+ * Used in __tdx_hypercall() to pass down and get back registers' values of
+ * the TDCALL instruction when requesting services from the VMM.
+ *
+ * This is a software only structure and not part of the TDX module/VMM ABI.
+ */
+struct tdx_hypercall_args {
+ u64 r10;
+ u64 r11;
+ u64 r12;
+ u64 r13;
+ u64 r14;
+ u64 r15;
+};
+
#ifdef CONFIG_INTEL_TDX_GUEST
void __init tdx_early_init(void);
+/* Used to communicate with the TDX module */
+u64 __tdx_module_call(u64 fn, u64 rcx, u64 rdx, u64 r8, u64 r9,
+ struct tdx_module_output *out);
+
+/* Used to request services from the VMM */
+u64 __tdx_hypercall(struct tdx_hypercall_args *args, unsigned long flags);
+
+/* Called from __tdx_hypercall() for unrecoverable failure */
+void __tdx_hypercall_failed(void);
+
#else
static inline void tdx_early_init(void) { };
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