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 #include <asm/segment.h>
   8
   9 #define WORD_SIZE (BITS_PER_LONG / 8)
  10
  11 #define VCPU_RAX        __VCPU_REGS_RAX * WORD_SIZE
  12 #define VCPU_RCX        __VCPU_REGS_RCX * WORD_SIZE
  13 #define VCPU_RDX        __VCPU_REGS_RDX * WORD_SIZE
  14 #define VCPU_RBX        __VCPU_REGS_RBX * WORD_SIZE
  15 /* Intentionally omit RSP as it's context switched by hardware */
  16 #define VCPU_RBP        __VCPU_REGS_RBP * WORD_SIZE
  17 #define VCPU_RSI        __VCPU_REGS_RSI * WORD_SIZE
  18 #define VCPU_RDI        __VCPU_REGS_RDI * WORD_SIZE
  19
  20 #ifdef CONFIG_X86_64
  21 #define VCPU_R8         __VCPU_REGS_R8  * WORD_SIZE
  22 #define VCPU_R9         __VCPU_REGS_R9  * WORD_SIZE
  23 #define VCPU_R10        __VCPU_REGS_R10 * WORD_SIZE
  24 #define VCPU_R11        __VCPU_REGS_R11 * WORD_SIZE
  25 #define VCPU_R12        __VCPU_REGS_R12 * WORD_SIZE
  26 #define VCPU_R13        __VCPU_REGS_R13 * WORD_SIZE
  27 #define VCPU_R14        __VCPU_REGS_R14 * WORD_SIZE
  28 #define VCPU_R15        __VCPU_REGS_R15 * WORD_SIZE
  29 #endif
  30
  31 .section .noinstr.text, "ax"
  32
  33 /**
  34  * vmx_vmenter - VM-Enter the current loaded VMCS
  35  *
  36  * %RFLAGS.ZF:  !VMCS.LAUNCHED, i.e. controls VMLAUNCH vs. VMRESUME
  37  *
  38  * Returns:
  39  *      %RFLAGS.CF is set on VM-Fail Invalid
  40  *      %RFLAGS.ZF is set on VM-Fail Valid
  41  *      %RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
  42  *
  43  * Note that VMRESUME/VMLAUNCH fall-through and return directly if
  44  * they VM-Fail, whereas a successful VM-Enter + VM-Exit will jump
  45  * to vmx_vmexit.
  46  */
  47 SYM_FUNC_START_LOCAL(vmx_vmenter)
  48         /* EFLAGS.ZF is set if VMCS.LAUNCHED == 0 */
  49         je 2f
  50
  51 1:      vmresume
  52         ret
  53
  54 2:      vmlaunch
  55         ret
  56
  57 3:      cmpb $0, kvm_rebooting
  58         je 4f
  59         ret
  60 4:      ud2
  61
  62         _ASM_EXTABLE(1b, 3b)
  63         _ASM_EXTABLE(2b, 3b)
  64
  65 SYM_FUNC_END(vmx_vmenter)
  66
  67 /**
  68  * vmx_vmexit - Handle a VMX VM-Exit
  69  *
  70  * Returns:
  71  *      %RFLAGS.{CF,ZF} are cleared on VM-Success, i.e. VM-Exit
  72  *
  73  * This is vmx_vmenter's partner in crime.  On a VM-Exit, control will jump
  74  * here after hardware loads the host's state, i.e. this is the destination
  75  * referred to by VMCS.HOST_RIP.
  76  */
  77 SYM_FUNC_START(vmx_vmexit)
  78 #ifdef CONFIG_RETPOLINE
  79         ALTERNATIVE "jmp .Lvmexit_skip_rsb", "", X86_FEATURE_RETPOLINE
  80         /* Preserve guest's RAX, it's used to stuff the RSB. */
  81         push %_ASM_AX
  82
  83         /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */
  84         FILL_RETURN_BUFFER %_ASM_AX, RSB_CLEAR_LOOPS, X86_FEATURE_RETPOLINE
  85
  86         /* Clear RFLAGS.CF and RFLAGS.ZF to preserve VM-Exit, i.e. !VM-Fail. */
  87         or $1, %_ASM_AX
  88
  89         pop %_ASM_AX
  90 .Lvmexit_skip_rsb:
  91 #endif
  92         ret
  93 SYM_FUNC_END(vmx_vmexit)
  94
  95 /**
  96  * __vmx_vcpu_run - Run a vCPU via a transition to VMX guest mode
  97  * @vmx:        struct vcpu_vmx * (forwarded to vmx_update_host_rsp)
  98  * @regs:       unsigned long * (to guest registers)
  99  * @launched:   %true if the VMCS has been launched
 100  *
 101  * Returns:
 102  *      0 on VM-Exit, 1 on VM-Fail
 103  */
 104 SYM_FUNC_START(__vmx_vcpu_run)
 105         push %_ASM_BP
 106         mov  %_ASM_SP, %_ASM_BP
 107 #ifdef CONFIG_X86_64
 108         push %r15
 109         push %r14
 110         push %r13
 111         push %r12
 112 #else
 113         push %edi
 114         push %esi
 115 #endif
 116         push %_ASM_BX
 117
 118         /*
 119          * Save @regs, _ASM_ARG2 may be modified by vmx_update_host_rsp() and
 120          * @regs is needed after VM-Exit to save the guest's register values.
 121          */
 122         push %_ASM_ARG2
 123
 124         /* Copy @launched to BL, _ASM_ARG3 is volatile. */
 125         mov %_ASM_ARG3B, %bl
 126
 127         /* Adjust RSP to account for the CALL to vmx_vmenter(). */
 128         lea -WORD_SIZE(%_ASM_SP), %_ASM_ARG2
 129         call vmx_update_host_rsp
 130
 131         /* Load @regs to RAX. */
 132         mov (%_ASM_SP), %_ASM_AX
 133
 134         /* Check if vmlaunch or vmresume is needed */
 135         testb %bl, %bl
 136
 137         /* Load guest registers.  Don't clobber flags. */
 138         mov VCPU_RCX(%_ASM_AX), %_ASM_CX
 139         mov VCPU_RDX(%_ASM_AX), %_ASM_DX
 140         mov VCPU_RBX(%_ASM_AX), %_ASM_BX
 141         mov VCPU_RBP(%_ASM_AX), %_ASM_BP
 142         mov VCPU_RSI(%_ASM_AX), %_ASM_SI
 143         mov VCPU_RDI(%_ASM_AX), %_ASM_DI
 144 #ifdef CONFIG_X86_64
 145         mov VCPU_R8 (%_ASM_AX),  %r8
 146         mov VCPU_R9 (%_ASM_AX),  %r9
 147         mov VCPU_R10(%_ASM_AX), %r10
 148         mov VCPU_R11(%_ASM_AX), %r11
 149         mov VCPU_R12(%_ASM_AX), %r12
 150         mov VCPU_R13(%_ASM_AX), %r13
 151         mov VCPU_R14(%_ASM_AX), %r14
 152         mov VCPU_R15(%_ASM_AX), %r15
 153 #endif
 154         /* Load guest RAX.  This kills the @regs pointer! */
 155         mov VCPU_RAX(%_ASM_AX), %_ASM_AX
 156
 157         /* Enter guest mode */
 158         call vmx_vmenter
 159
 160         /* Jump on VM-Fail. */
 161         jbe 2f
 162
 163         /* Temporarily save guest's RAX. */
 164         push %_ASM_AX
 165
 166         /* Reload @regs to RAX. */
 167         mov WORD_SIZE(%_ASM_SP), %_ASM_AX
 168
 169         /* Save all guest registers, including RAX from the stack */
 170         pop           VCPU_RAX(%_ASM_AX)
 171         mov %_ASM_CX, VCPU_RCX(%_ASM_AX)
 172         mov %_ASM_DX, VCPU_RDX(%_ASM_AX)
 173         mov %_ASM_BX, VCPU_RBX(%_ASM_AX)
 174         mov %_ASM_BP, VCPU_RBP(%_ASM_AX)
 175         mov %_ASM_SI, VCPU_RSI(%_ASM_AX)
 176         mov %_ASM_DI, VCPU_RDI(%_ASM_AX)
 177 #ifdef CONFIG_X86_64
 178         mov %r8,  VCPU_R8 (%_ASM_AX)
 179         mov %r9,  VCPU_R9 (%_ASM_AX)
 180         mov %r10, VCPU_R10(%_ASM_AX)
 181         mov %r11, VCPU_R11(%_ASM_AX)
 182         mov %r12, VCPU_R12(%_ASM_AX)
 183         mov %r13, VCPU_R13(%_ASM_AX)
 184         mov %r14, VCPU_R14(%_ASM_AX)
 185         mov %r15, VCPU_R15(%_ASM_AX)
 186 #endif
 187
 188         /* Clear RAX to indicate VM-Exit (as opposed to VM-Fail). */
 189         xor %eax, %eax
 190
 191         /*
 192          * Clear all general purpose registers except RSP and RAX to prevent
 193          * speculative use of the guest's values, even those that are reloaded
 194          * via the stack.  In theory, an L1 cache miss when restoring registers
 195          * could lead to speculative execution with the guest's values.
 196          * Zeroing XORs are dirt cheap, i.e. the extra paranoia is essentially
 197          * free.  RSP and RAX are exempt as RSP is restored by hardware during
 198          * VM-Exit and RAX is explicitly loaded with 0 or 1 to return VM-Fail.
 199          */
 200 1:      xor %ecx, %ecx
 201         xor %edx, %edx
 202         xor %ebx, %ebx
 203         xor %ebp, %ebp
 204         xor %esi, %esi
 205         xor %edi, %edi
 206 #ifdef CONFIG_X86_64
 207         xor %r8d,  %r8d
 208         xor %r9d,  %r9d
 209         xor %r10d, %r10d
 210         xor %r11d, %r11d
 211         xor %r12d, %r12d
 212         xor %r13d, %r13d
 213         xor %r14d, %r14d
 214         xor %r15d, %r15d
 215 #endif
 216
 217         /* "POP" @regs. */
 218         add $WORD_SIZE, %_ASM_SP
 219         pop %_ASM_BX
 220
 221 #ifdef CONFIG_X86_64
 222         pop %r12
 223         pop %r13
 224         pop %r14
 225         pop %r15
 226 #else
 227         pop %esi
 228         pop %edi
 229 #endif
 230         pop %_ASM_BP
 231         ret
 232
 233         /* VM-Fail.  Out-of-line to avoid a taken Jcc after VM-Exit. */
 234 2:      mov $1, %eax
 235         jmp 1b
 236 SYM_FUNC_END(__vmx_vcpu_run)
 237
 238
 239 .section .text, "ax"
 240
 241 /**
 242  * vmread_error_trampoline - Trampoline from inline asm to vmread_error()
 243  * @field:      VMCS field encoding that failed
 244  * @fault:      %true if the VMREAD faulted, %false if it failed
 245
 246  * Save and restore volatile registers across a call to vmread_error().  Note,
 247  * all parameters are passed on the stack.
 248  */
 249 SYM_FUNC_START(vmread_error_trampoline)
 250         push %_ASM_BP
 251         mov  %_ASM_SP, %_ASM_BP
 252
 253         push %_ASM_AX
 254         push %_ASM_CX
 255         push %_ASM_DX
 256 #ifdef CONFIG_X86_64
 257         push %rdi
 258         push %rsi
 259         push %r8
 260         push %r9
 261         push %r10
 262         push %r11
 263 #endif
 264 #ifdef CONFIG_X86_64
 265         /* Load @field and @fault to arg1 and arg2 respectively. */
 266         mov 3*WORD_SIZE(%rbp), %_ASM_ARG2
 267         mov 2*WORD_SIZE(%rbp), %_ASM_ARG1
 268 #else
 269         /* Parameters are passed on the stack for 32-bit (see asmlinkage). */
 270         push 3*WORD_SIZE(%ebp)
 271         push 2*WORD_SIZE(%ebp)
 272 #endif
 273
 274         call vmread_error
 275
 276 #ifndef CONFIG_X86_64
 277         add $8, %esp
 278 #endif
 279
 280         /* Zero out @fault, which will be popped into the result register. */
 281         _ASM_MOV $0, 3*WORD_SIZE(%_ASM_BP)
 282
 283 #ifdef CONFIG_X86_64
 284         pop %r11
 285         pop %r10
 286         pop %r9
 287         pop %r8
 288         pop %rsi
 289         pop %rdi
 290 #endif
 291         pop %_ASM_DX
 292         pop %_ASM_CX
 293         pop %_ASM_AX
 294         pop %_ASM_BP
 295
 296         ret
 297 SYM_FUNC_END(vmread_error_trampoline)
 298
 299 SYM_FUNC_START(vmx_do_interrupt_nmi_irqoff)
 300         /*
 301          * Unconditionally create a stack frame, getting the correct RSP on the
 302          * stack (for x86-64) would take two instructions anyways, and RBP can
 303          * be used to restore RSP to make objtool happy (see below).
 304          */
 305         push %_ASM_BP
 306         mov %_ASM_SP, %_ASM_BP
 307
 308 #ifdef CONFIG_X86_64
 309         /*
 310          * Align RSP to a 16-byte boundary (to emulate CPU behavior) before
 311          * creating the synthetic interrupt stack frame for the IRQ/NMI.
 312          */
 313         and  $-16, %rsp
 314         push $__KERNEL_DS
 315         push %rbp
 316 #endif
 317         pushf
 318         push $__KERNEL_CS
 319         CALL_NOSPEC _ASM_ARG1
 320
 321         /*
 322          * "Restore" RSP from RBP, even though IRET has already unwound RSP to
 323          * the correct value.  objtool doesn't know the callee will IRET and,
 324          * without the explicit restore, thinks the stack is getting walloped.
 325          * Using an unwind hint is problematic due to x86-64's dynamic alignment.
 326          */
 327         mov %_ASM_BP, %_ASM_SP
 328         pop %_ASM_BP
 329         ret
 330 SYM_FUNC_END(vmx_do_interrupt_nmi_irqoff)