1/* SPDX-License-Identifier: GPL-2.0 */ 2#include <asm/asm-offsets.h> 3#include <asm/asm.h> 4#include <asm/frame.h> 5#include <asm/unwind_hints.h> 6 7#include <linux/linkage.h> 8#include <linux/bits.h> 9#include <linux/errno.h> 10 11#include "../../virt/vmx/tdx/tdxcall.S" 12 13/* 14 * Bitmasks of exposed registers (with VMM). 15 */ 16#define TDX_R10 BIT(10) 17#define TDX_R11 BIT(11) 18#define TDX_R12 BIT(12) 19#define TDX_R13 BIT(13) 20#define TDX_R14 BIT(14) 21#define TDX_R15 BIT(15) 22 23/* 24 * These registers are clobbered to hold arguments for each 25 * TDVMCALL. They are safe to expose to the VMM. 26 * Each bit in this mask represents a register ID. Bit field 27 * details can be found in TDX GHCI specification, section 28 * titled "TDCALL [TDG.VP.VMCALL] leaf". 29 */ 30#define TDVMCALL_EXPOSE_REGS_MASK ( TDX_R10 | TDX_R11 | \ 31 TDX_R12 | TDX_R13 | \ 32 TDX_R14 | TDX_R15 ) 33 34.section .noinstr.text, "ax" 35 36/* 37 * __tdx_module_call() - Used by TDX guests to request services from 38 * the TDX module (does not include VMM services) using TDCALL instruction. 39 * 40 * Transforms function call register arguments into the TDCALL register ABI. 41 * After TDCALL operation, TDX module output is saved in @out (if it is 42 * provided by the user). 43 * 44 *------------------------------------------------------------------------- 45 * TDCALL ABI: 46 *------------------------------------------------------------------------- 47 * Input Registers: 48 * 49 * RAX - TDCALL Leaf number. 50 * RCX,RDX,R8-R9 - TDCALL Leaf specific input registers. 51 * 52 * Output Registers: 53 * 54 * RAX - TDCALL instruction error code. 55 * RCX,RDX,R8-R11 - TDCALL Leaf specific output registers. 56 * 57 *------------------------------------------------------------------------- 58 * 59 * __tdx_module_call() function ABI: 60 * 61 * @fn (RDI) - TDCALL Leaf ID, moved to RAX 62 * @rcx (RSI) - Input parameter 1, moved to RCX 63 * @rdx (RDX) - Input parameter 2, moved to RDX 64 * @r8 (RCX) - Input parameter 3, moved to R8 65 * @r9 (R8) - Input parameter 4, moved to R9 66 * 67 * @out (R9) - struct tdx_module_output pointer 68 * stored temporarily in R12 (not 69 * shared with the TDX module). It 70 * can be NULL. 71 * 72 * Return status of TDCALL via RAX. 73 */ 74SYM_FUNC_START(__tdx_module_call) 75 FRAME_BEGIN 76 TDX_MODULE_CALL host=0 77 FRAME_END 78 RET 79SYM_FUNC_END(__tdx_module_call) 80 81/* 82 * __tdx_hypercall() - Make hypercalls to a TDX VMM using TDVMCALL leaf 83 * of TDCALL instruction 84 * 85 * Transforms values in function call argument struct tdx_hypercall_args @args 86 * into the TDCALL register ABI. After TDCALL operation, VMM output is saved 87 * back in @args. 88 * 89 *------------------------------------------------------------------------- 90 * TD VMCALL ABI: 91 *------------------------------------------------------------------------- 92 * 93 * Input Registers: 94 * 95 * RAX - TDCALL instruction leaf number (0 - TDG.VP.VMCALL) 96 * RCX - BITMAP which controls which part of TD Guest GPR 97 * is passed as-is to the VMM and back. 98 * R10 - Set 0 to indicate TDCALL follows standard TDX ABI 99 * specification. Non zero value indicates vendor 100 * specific ABI. 101 * R11 - VMCALL sub function number 102 * RBX, RBP, RDI, RSI - Used to pass VMCALL sub function specific arguments. 103 * R8-R9, R12-R15 - Same as above. 104 * 105 * Output Registers: 106 * 107 * RAX - TDCALL instruction status (Not related to hypercall 108 * output). 109 * R10 - Hypercall output error code. 110 * R11-R15 - Hypercall sub function specific output values. 111 * 112 *------------------------------------------------------------------------- 113 * 114 * __tdx_hypercall() function ABI: 115 * 116 * @args (RDI) - struct tdx_hypercall_args for input and output 117 * @flags (RSI) - TDX_HCALL_* flags 118 * 119 * On successful completion, return the hypercall error code. 120 */ 121SYM_FUNC_START(__tdx_hypercall) 122 FRAME_BEGIN 123 124 /* Save callee-saved GPRs as mandated by the x86_64 ABI */ 125 push %r15 126 push %r14 127 push %r13 128 push %r12 129 130 /* Mangle function call ABI into TDCALL ABI: */ 131 /* Set TDCALL leaf ID (TDVMCALL (0)) in RAX */ 132 xor %eax, %eax 133 134 /* Copy hypercall registers from arg struct: */ 135 movq TDX_HYPERCALL_r10(%rdi), %r10 136 movq TDX_HYPERCALL_r11(%rdi), %r11 137 movq TDX_HYPERCALL_r12(%rdi), %r12 138 movq TDX_HYPERCALL_r13(%rdi), %r13 139 movq TDX_HYPERCALL_r14(%rdi), %r14 140 movq TDX_HYPERCALL_r15(%rdi), %r15 141 142 movl $TDVMCALL_EXPOSE_REGS_MASK, %ecx 143 144 tdcall 145 146 /* 147 * RAX==0 indicates a failure of the TDVMCALL mechanism itself and that 148 * something has gone horribly wrong with the TDX module. 149 * 150 * The return status of the hypercall operation is in a separate 151 * register (in R10). Hypercall errors are a part of normal operation 152 * and are handled by callers. 153 */ 154 testq %rax, %rax 155 jne .Lpanic 156 157 /* TDVMCALL leaf return code is in R10 */ 158 movq %r10, %rax 159 160 /* Copy hypercall result registers to arg struct if needed */ 161 testq $TDX_HCALL_HAS_OUTPUT, %rsi 162 jz .Lout 163 164 movq %r10, TDX_HYPERCALL_r10(%rdi) 165 movq %r11, TDX_HYPERCALL_r11(%rdi) 166 movq %r12, TDX_HYPERCALL_r12(%rdi) 167 movq %r13, TDX_HYPERCALL_r13(%rdi) 168 movq %r14, TDX_HYPERCALL_r14(%rdi) 169 movq %r15, TDX_HYPERCALL_r15(%rdi) 170.Lout: 171 /* 172 * Zero out registers exposed to the VMM to avoid speculative execution 173 * with VMM-controlled values. This needs to include all registers 174 * present in TDVMCALL_EXPOSE_REGS_MASK (except R12-R15). R12-R15 175 * context will be restored. 176 */ 177 xor %r10d, %r10d 178 xor %r11d, %r11d 179 180 /* Restore callee-saved GPRs as mandated by the x86_64 ABI */ 181 pop %r12 182 pop %r13 183 pop %r14 184 pop %r15 185 186 FRAME_END 187 188 RET 189.Lpanic: 190 call __tdx_hypercall_failed 191 /* __tdx_hypercall_failed never returns */ 192 REACHABLE 193 jmp .Lpanic 194SYM_FUNC_END(__tdx_hypercall) 195