arch/x86/kvm/vmx/vmenter.S

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #include <linux/linkage.h>
   3 #include <asm/asm.h>
   4 #include <asm/bitsperlong.h>
   5 #include <asm/kvm_vcpu_regs.h>
   6 #include <asm/nospec-branch.h>
   7
   8 #define WORD_SIZE (BITS_PER_LONG / 8)
   9
  10 #define VCPU_RAX        __VCPU_REGS_RAX * WORD_SIZE
  11 #define VCPU_RCX        __VCPU_REGS_RCX * WORD_SIZE
  12 #define VCPU_RDX        __VCPU_REGS_RDX * WORD_SIZE
  13 #define VCPU_RBX        __VCPU_REGS_RBX * WORD_SIZE
  14 /* Intentionally omit RSP as it's context switched by hardware */
  15 #define VCPU_RBP        __VCPU_REGS_RBP * WORD_SIZE
  16 #define VCPU_RSI        __VCPU_REGS_RSI * WORD_SIZE
  17 #define VCPU_RDI        __VCPU_REGS_RDI * WORD_SIZE
  18
  19 #ifdef CONFIG_X86_64
  20 #define VCPU_R8         __VCPU_REGS_R8  * WORD_SIZE
  21 #define VCPU_R9         __VCPU_REGS_R9  * WORD_SIZE
  22 #define VCPU_R10        __VCPU_REGS_R10 * WORD_SIZE
  23 #define VCPU_R11        __VCPU_REGS_R11 * WORD_SIZE
  24 #define VCPU_R12        __VCPU_REGS_R12 * WORD_SIZE
  25 #define VCPU_R13        __VCPU_REGS_R13 * WORD_SIZE
  26 #define VCPU_R14        __VCPU_REGS_R14 * WORD_SIZE
  27 #define VCPU_R15        __VCPU_REGS_R15 * WORD_SIZE
  28 #endif
  29
  30         .text
  31
  32 /**
  33  * vmx_vmenter - VM-Enter the current loaded VMCS
  34  *
  35  * %RFLAGS.ZF:  !VMCS.LAUNCHED, i.e. controls VMLAUNCH vs. VMRESUME
  36  *
  37  * Returns:
  38  *      %RFLAGS.CF is set on VM-Fail Invalid
  39  *      %RFLAGS.ZF is set on VM-Fail Valid
  40  *      %RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
  41  *
  42  * Note that VMRESUME/VMLAUNCH fall-through and return directly if
  43  * they VM-Fail, whereas a successful VM-Enter + VM-Exit will jump
  44  * to vmx_vmexit.
  45  */
  46 SYM_FUNC_START(vmx_vmenter)
  47         /* EFLAGS.ZF is set if VMCS.LAUNCHED == 0 */
  48         je 2f
  49
  50 1:      vmresume
  51         ret
  52
  53 2:      vmlaunch
  54         ret
  55
  56 3:      cmpb $0, kvm_rebooting
  57         je 4f
  58         ret
  59 4:      ud2
  60
  61         _ASM_EXTABLE(1b, 3b)
  62         _ASM_EXTABLE(2b, 3b)
  63
  64 SYM_FUNC_END(vmx_vmenter)
  65
  66 /**
  67  * vmx_vmexit - Handle a VMX VM-Exit
  68  *
  69  * Returns:
  70  *      %RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
  71  *
  72  * This is vmx_vmenter's partner in crime.  On a VM-Exit, control will jump
  73  * here after hardware loads the host's state, i.e. this is the destination
  74  * referred to by VMCS.HOST_RIP.
  75  */
  76 SYM_FUNC_START(vmx_vmexit)
  77 #ifdef CONFIG_RETPOLINE
  78         ALTERNATIVE "jmp .Lvmexit_skip_rsb", "", X86_FEATURE_RETPOLINE
  79         /* Preserve guest's RAX, it's used to stuff the RSB. */
  80         push %_ASM_AX
  81
  82         /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
  83         FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
  84
  85         /* Clear RFLAGS.CF and RFLAGS.ZF to preserve VM-Exit, i.e. !VM-Fail. */
  86         or $1, %_ASM_AX
  87
  88         pop %_ASM_AX
  89 .Lvmexit_skip_rsb:
  90 #endif
  91         ret
  92 SYM_FUNC_END(vmx_vmexit)
  93
  94 /**
  95  * __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
  96  * @vmx:        struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
  97  * @regs:       unsigned long * (to guest registers)
  98  * @launched:   %true if the VMCS has been launched
  99  *
 100  * Returns:
 101  *      0 on VM-Exit, 1 on VM-Fail
 102  */
 103 SYM_FUNC_START(__vmx_vcpu_run)
 104         push %_ASM_BP
 105         mov  %_ASM_SP, %_ASM_BP
 106 #ifdef CONFIG_X86_64
 107         push %r15
 108         push %r14
 109         push %r13
 110         push %r12
 111 #else
 112         push %edi
 113         push %esi
 114 #endif
 115         push %_ASM_BX
 116
 117         /*
 118          * Save @regs, _ASM_ARG2 may be modified by vmx_update_host_rsp() and
 119          * @regs is needed after VM-Exit to save the guest's register values.
 120          */
 121         push %_ASM_ARG2
 122
 123         /* Copy @launched to BL, _ASM_ARG3 is volatile. */
 124         mov %_ASM_ARG3B, %bl
 125
 126         /* Adjust RSP to account for the CALL to vmx_vmenter(). */
 127         lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
 128         call vmx_update_host_rsp
 129
 130         /* Load @regs to RAX. */
 131         mov (%_ASM_SP), %_ASM_AX
 132
 133         /* Check if vmlaunch or vmresume is needed */
 134         cmpb $0, %bl
 135
 136         /* Load guest registers.  Don't clobber flags. */
 137         mov VCPU_RCX(%_ASM_AX), %_ASM_CX
 138         mov VCPU_RDX(%_ASM_AX), %_ASM_DX
 139         mov VCPU_RBX(%_ASM_AX), %_ASM_BX
 140         mov VCPU_RBP(%_ASM_AX), %_ASM_BP
 141         mov VCPU_RSI(%_ASM_AX), %_ASM_SI
 142         mov VCPU_RDI(%_ASM_AX), %_ASM_DI
 143 #ifdef CONFIG_X86_64
 144         mov VCPU_R8 (%_ASM_AX),  %r8
 145         mov VCPU_R9 (%_ASM_AX),  %r9
 146         mov VCPU_R10(%_ASM_AX), %r10
 147         mov VCPU_R11(%_ASM_AX), %r11
 148         mov VCPU_R12(%_ASM_AX), %r12
 149         mov VCPU_R13(%_ASM_AX), %r13
 150         mov VCPU_R14(%_ASM_AX), %r14
 151         mov VCPU_R15(%_ASM_AX), %r15
 152 #endif
 153         /* Load guest RAX.  This kills the @regs pointer! */
 154         mov VCPU_RAX(%_ASM_AX), %_ASM_AX
 155
 156         /* Enter guest mode */
 157         call vmx_vmenter
 158
 159         /* Jump on VM-Fail. */
 160         jbe 2f
 161
 162         /* Temporarily save guest's RAX. */
 163         push %_ASM_AX
 164
 165         /* Reload @regs to RAX. */
 166         mov WORD_SIZE(%_ASM_SP), %_ASM_AX
 167
 168         /* Save all guest registers, including RAX from the stack */
 169         __ASM_SIZE(pop) VCPU_RAX(%_ASM_AX)
 170         mov %_ASM_CX,   VCPU_RCX(%_ASM_AX)
 171         mov %_ASM_DX,   VCPU_RDX(%_ASM_AX)
 172         mov %_ASM_BX,   VCPU_RBX(%_ASM_AX)
 173         mov %_ASM_BP,   VCPU_RBP(%_ASM_AX)
 174         mov %_ASM_SI,   VCPU_RSI(%_ASM_AX)
 175         mov %_ASM_DI,   VCPU_RDI(%_ASM_AX)
 176 #ifdef CONFIG_X86_64
 177         mov %r8,  VCPU_R8 (%_ASM_AX)
 178         mov %r9,  VCPU_R9 (%_ASM_AX)
 179         mov %r10, VCPU_R10(%_ASM_AX)
 180         mov %r11, VCPU_R11(%_ASM_AX)
 181         mov %r12, VCPU_R12(%_ASM_AX)
 182         mov %r13, VCPU_R13(%_ASM_AX)
 183         mov %r14, VCPU_R14(%_ASM_AX)
 184         mov %r15, VCPU_R15(%_ASM_AX)
 185 #endif
 186
 187         /* Clear RAX to indicate VM-Exit (as opposed to VM-Fail). */
 188         xor %eax, %eax
 189
 190         /*
 191          * Clear all general purpose registers except RSP and RAX to prevent
 192          * speculative use of the guest's values, even those that are reloaded
 193          * via the stack.  In theory, an L1 cache miss when restoring registers
 194          * could lead to speculative execution with the guest's values.
 195          * Zeroing XORs are dirt cheap, i.e. the extra paranoia is essentially
 196          * free.  RSP and RAX are exempt as RSP is restored by hardware during
 197          * VM-Exit and RAX is explicitly loaded with 0 or 1 to return VM-Fail.
 198          */
 199 1:      xor %ecx, %ecx
 200         xor %edx, %edx
 201         xor %ebx, %ebx
 202         xor %ebp, %ebp
 203         xor %esi, %esi
 204         xor %edi, %edi
 205 #ifdef CONFIG_X86_64
 206         xor %r8d,  %r8d
 207         xor %r9d,  %r9d
 208         xor %r10d, %r10d
 209         xor %r11d, %r11d
 210         xor %r12d, %r12d
 211         xor %r13d, %r13d
 212         xor %r14d, %r14d
 213         xor %r15d, %r15d
 214 #endif
 215
 216         /* "POP" @regs. */
 217         add $WORD_SIZE, %_ASM_SP
 218         pop %_ASM_BX
 219
 220 #ifdef CONFIG_X86_64
 221         pop %r12
 222         pop %r13
 223         pop %r14
 224         pop %r15
 225 #else
 226         pop %esi
 227         pop %edi
 228 #endif
 229         pop %_ASM_BP
 230         ret
 231
 232         /* VM-Fail.  Out-of-line to avoid a taken Jcc after VM-Exit. */
 233 2:      mov $1, %eax
 234         jmp 1b
 235 SYM_FUNC_END(__vmx_vcpu_run)
 236
 237 /**
 238  * vmread_error_trampoline - Trampoline from inline asm to vmread_error()
 239  * @field:      VMCS field encoding that failed
 240  * @fault:      %true if the VMREAD faulted, %false if it failed
 241
 242  * Save and restore volatile registers across a call to vmread_error().  Note,
 243  * all parameters are passed on the stack.
 244  */
 245 SYM_FUNC_START(vmread_error_trampoline)
 246         push %_ASM_BP
 247         mov  %_ASM_SP, %_ASM_BP
 248
 249         push %_ASM_AX
 250         push %_ASM_CX
 251         push %_ASM_DX
 252 #ifdef CONFIG_X86_64
 253         push %rdi
 254         push %rsi
 255         push %r8
 256         push %r9
 257         push %r10
 258         push %r11
 259 #endif
 260 #ifdef CONFIG_X86_64
 261         /* Load @field and @fault to arg1 and arg2 respectively. */
 262         mov 3*WORD_SIZE(%rbp), %_ASM_ARG2
 263         mov 2*WORD_SIZE(%rbp), %_ASM_ARG1
 264 #else
 265         /* Parameters are passed on the stack for 32-bit (see asmlinkage). */
 266         push 3*WORD_SIZE(%ebp)
 267         push 2*WORD_SIZE(%ebp)
 268 #endif
 269
 270         call vmread_error
 271
 272 #ifndef CONFIG_X86_64
 273         add $8, %esp
 274 #endif
 275
 276         /* Zero out @fault, which will be popped into the result register. */
 277         _ASM_MOV $0, 3*WORD_SIZE(%_ASM_BP)
 278
 279 #ifdef CONFIG_X86_64
 280         pop %r11
 281         pop %r10
 282         pop %r9
 283         pop %r8
 284         pop %rsi
 285         pop %rdi
 286 #endif
 287         pop %_ASM_DX
 288         pop %_ASM_CX
 289         pop %_ASM_AX
 290         pop %_ASM_BP
 291
 292         ret
 293 SYM_FUNC_END(vmread_error_trampoline)