arch/arm64/kvm/handle_exit.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2012,2013 - ARM Ltd
   4  * Author: Marc Zyngier <marc.zyngier@arm.com>
   5  *
   6  * Derived from arch/arm/kvm/handle_exit.c:
   7  * Copyright (C) 2012 - Virtual Open Systems and Columbia University
   8  * Author: Christoffer Dall <c.dall@virtualopensystems.com>
   9  */
  10
  11 #include <linux/kvm.h>
  12 #include <linux/kvm_host.h>
  13
  14 #include <asm/esr.h>
  15 #include <asm/exception.h>
  16 #include <asm/kvm_asm.h>
  17 #include <asm/kvm_emulate.h>
  18 #include <asm/kvm_mmu.h>
  19 #include <asm/debug-monitors.h>
  20 #include <asm/traps.h>
  21
  22 #include <kvm/arm_hypercalls.h>
  23
  24 #define CREATE_TRACE_POINTS
  25 #include "trace_handle_exit.h"
  26
  27 typedef int (*exit_handle_fn)(struct kvm_vcpu *);
  28
  29 static void kvm_handle_guest_serror(struct kvm_vcpu *vcpu, u32 esr)
  30 {
  31         if (!arm64_is_ras_serror(esr) || arm64_is_fatal_ras_serror(NULL, esr))
  32                 kvm_inject_vabt(vcpu);
  33 }
  34
  35 static int handle_hvc(struct kvm_vcpu *vcpu)
  36 {
  37         int ret;
  38
  39         trace_kvm_hvc_arm64(*vcpu_pc(vcpu), vcpu_get_reg(vcpu, 0),
  40                             kvm_vcpu_hvc_get_imm(vcpu));
  41         vcpu->stat.hvc_exit_stat++;
  42
  43         ret = kvm_hvc_call_handler(vcpu);
  44         if (ret < 0) {
  45                 vcpu_set_reg(vcpu, 0, ~0UL);
  46                 return 1;
  47         }
  48
  49         return ret;
  50 }
  51
  52 static int handle_smc(struct kvm_vcpu *vcpu)
  53 {
  54         /*
  55          * "If an SMC instruction executed at Non-secure EL1 is
  56          * trapped to EL2 because HCR_EL2.TSC is 1, the exception is a
  57          * Trap exception, not a Secure Monitor Call exception [...]"
  58          *
  59          * We need to advance the PC after the trap, as it would
  60          * otherwise return to the same address...
  61          */
  62         vcpu_set_reg(vcpu, 0, ~0UL);
  63         kvm_incr_pc(vcpu);
  64         return 1;
  65 }
  66
  67 /*
  68  * Guest access to FP/ASIMD registers are routed to this handler only
  69  * when the system doesn't support FP/ASIMD.
  70  */
  71 static int handle_no_fpsimd(struct kvm_vcpu *vcpu)
  72 {
  73         kvm_inject_undefined(vcpu);
  74         return 1;
  75 }
  76
  77 /**
  78  * kvm_handle_wfx - handle a wait-for-interrupts or wait-for-event
  79  *                  instruction executed by a guest
  80  *
  81  * @vcpu:       the vcpu pointer
  82  *
  83  * WFE: Yield the CPU and come back to this vcpu when the scheduler
  84  * decides to.
  85  * WFI: Simply call kvm_vcpu_block(), which will halt execution of
  86  * world-switches and schedule other host processes until there is an
  87  * incoming IRQ or FIQ to the VM.
  88  */
  89 static int kvm_handle_wfx(struct kvm_vcpu *vcpu)
  90 {
  91         if (kvm_vcpu_get_esr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
  92                 trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
  93                 vcpu->stat.wfe_exit_stat++;
  94                 kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
  95         } else {
  96                 trace_kvm_wfx_arm64(*vcpu_pc(vcpu), false);
  97                 vcpu->stat.wfi_exit_stat++;
  98                 kvm_vcpu_block(vcpu);
  99                 kvm_clear_request(KVM_REQ_UNHALT, vcpu);
 100         }
 101
 102         kvm_incr_pc(vcpu);
 103
 104         return 1;
 105 }
 106
 107 /**
 108  * kvm_handle_guest_debug - handle a debug exception instruction
 109  *
 110  * @vcpu:       the vcpu pointer
 111  *
 112  * We route all debug exceptions through the same handler. If both the
 113  * guest and host are using the same debug facilities it will be up to
 114  * userspace to re-inject the correct exception for guest delivery.
 115  *
 116  * @return: 0 (while setting vcpu->run->exit_reason), -1 for error
 117  */
 118 static int kvm_handle_guest_debug(struct kvm_vcpu *vcpu)
 119 {
 120         struct kvm_run *run = vcpu->run;
 121         u32 esr = kvm_vcpu_get_esr(vcpu);
 122         int ret = 0;
 123
 124         run->exit_reason = KVM_EXIT_DEBUG;
 125         run->debug.arch.hsr = esr;
 126
 127         switch (ESR_ELx_EC(esr)) {
 128         case ESR_ELx_EC_WATCHPT_LOW:
 129                 run->debug.arch.far = vcpu->arch.fault.far_el2;
 130                 fallthrough;
 131         case ESR_ELx_EC_SOFTSTP_LOW:
 132         case ESR_ELx_EC_BREAKPT_LOW:
 133         case ESR_ELx_EC_BKPT32:
 134         case ESR_ELx_EC_BRK64:
 135                 break;
 136         default:
 137                 kvm_err("%s: un-handled case esr: %#08x\n",
 138                         __func__, (unsigned int) esr);
 139                 ret = -1;
 140                 break;
 141         }
 142
 143         return ret;
 144 }
 145
 146 static int kvm_handle_unknown_ec(struct kvm_vcpu *vcpu)
 147 {
 148         u32 esr = kvm_vcpu_get_esr(vcpu);
 149
 150         kvm_pr_unimpl("Unknown exception class: esr: %#08x -- %s\n",
 151                       esr, esr_get_class_string(esr));
 152
 153         kvm_inject_undefined(vcpu);
 154         return 1;
 155 }
 156
 157 static int handle_sve(struct kvm_vcpu *vcpu)
 158 {
 159         /* Until SVE is supported for guests: */
 160         kvm_inject_undefined(vcpu);
 161         return 1;
 162 }
 163
 164 /*
 165  * Guest usage of a ptrauth instruction (which the guest EL1 did not turn into
 166  * a NOP). If we get here, it is that we didn't fixup ptrauth on exit, and all
 167  * that we can do is give the guest an UNDEF.
 168  */
 169 static int kvm_handle_ptrauth(struct kvm_vcpu *vcpu)
 170 {
 171         kvm_inject_undefined(vcpu);
 172         return 1;
 173 }
 174
 175 static exit_handle_fn arm_exit_handlers[] = {
 176         [0 ... ESR_ELx_EC_MAX]  = kvm_handle_unknown_ec,
 177         [ESR_ELx_EC_WFx]        = kvm_handle_wfx,
 178         [ESR_ELx_EC_CP15_32]    = kvm_handle_cp15_32,
 179         [ESR_ELx_EC_CP15_64]    = kvm_handle_cp15_64,
 180         [ESR_ELx_EC_CP14_MR]    = kvm_handle_cp14_32,
 181         [ESR_ELx_EC_CP14_LS]    = kvm_handle_cp14_load_store,
 182         [ESR_ELx_EC_CP14_64]    = kvm_handle_cp14_64,
 183         [ESR_ELx_EC_HVC32]      = handle_hvc,
 184         [ESR_ELx_EC_SMC32]      = handle_smc,
 185         [ESR_ELx_EC_HVC64]      = handle_hvc,
 186         [ESR_ELx_EC_SMC64]      = handle_smc,
 187         [ESR_ELx_EC_SYS64]      = kvm_handle_sys_reg,
 188         [ESR_ELx_EC_SVE]        = handle_sve,
 189         [ESR_ELx_EC_IABT_LOW]   = kvm_handle_guest_abort,
 190         [ESR_ELx_EC_DABT_LOW]   = kvm_handle_guest_abort,
 191         [ESR_ELx_EC_SOFTSTP_LOW]= kvm_handle_guest_debug,
 192         [ESR_ELx_EC_WATCHPT_LOW]= kvm_handle_guest_debug,
 193         [ESR_ELx_EC_BREAKPT_LOW]= kvm_handle_guest_debug,
 194         [ESR_ELx_EC_BKPT32]     = kvm_handle_guest_debug,
 195         [ESR_ELx_EC_BRK64]      = kvm_handle_guest_debug,
 196         [ESR_ELx_EC_FP_ASIMD]   = handle_no_fpsimd,
 197         [ESR_ELx_EC_PAC]        = kvm_handle_ptrauth,
 198 };
 199
 200 static exit_handle_fn kvm_get_exit_handler(struct kvm_vcpu *vcpu)
 201 {
 202         u32 esr = kvm_vcpu_get_esr(vcpu);
 203         u8 esr_ec = ESR_ELx_EC(esr);
 204
 205         return arm_exit_handlers[esr_ec];
 206 }
 207
 208 /*
 209  * We may be single-stepping an emulated instruction. If the emulation
 210  * has been completed in the kernel, we can return to userspace with a
 211  * KVM_EXIT_DEBUG, otherwise userspace needs to complete its
 212  * emulation first.
 213  */
 214 static int handle_trap_exceptions(struct kvm_vcpu *vcpu)
 215 {
 216         int handled;
 217
 218         /*
 219          * See ARM ARM B1.14.1: "Hyp traps on instructions
 220          * that fail their condition code check"
 221          */
 222         if (!kvm_condition_valid(vcpu)) {
 223                 kvm_incr_pc(vcpu);
 224                 handled = 1;
 225         } else {
 226                 exit_handle_fn exit_handler;
 227
 228                 exit_handler = kvm_get_exit_handler(vcpu);
 229                 handled = exit_handler(vcpu);
 230         }
 231
 232         return handled;
 233 }
 234
 235 /*
 236  * Return > 0 to return to guest, < 0 on error, 0 (and set exit_reason) on
 237  * proper exit to userspace.
 238  */
 239 int handle_exit(struct kvm_vcpu *vcpu, int exception_index)
 240 {
 241         struct kvm_run *run = vcpu->run;
 242
 243         exception_index = ARM_EXCEPTION_CODE(exception_index);
 244
 245         switch (exception_index) {
 246         case ARM_EXCEPTION_IRQ:
 247                 return 1;
 248         case ARM_EXCEPTION_EL1_SERROR:
 249                 return 1;
 250         case ARM_EXCEPTION_TRAP:
 251                 return handle_trap_exceptions(vcpu);
 252         case ARM_EXCEPTION_HYP_GONE:
 253                 /*
 254                  * EL2 has been reset to the hyp-stub. This happens when a guest
 255                  * is pre-empted by kvm_reboot()'s shutdown call.
 256                  */
 257                 run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 258                 return 0;
 259         case ARM_EXCEPTION_IL:
 260                 /*
 261                  * We attempted an illegal exception return.  Guest state must
 262                  * have been corrupted somehow.  Give up.
 263                  */
 264                 run->exit_reason = KVM_EXIT_FAIL_ENTRY;
 265                 return -EINVAL;
 266         default:
 267                 kvm_pr_unimpl("Unsupported exception type: %d",
 268                               exception_index);
 269                 run->exit_reason = KVM_EXIT_INTERNAL_ERROR;
 270                 return 0;
 271         }
 272 }
 273
 274 /* For exit types that need handling before we can be preempted */
 275 void handle_exit_early(struct kvm_vcpu *vcpu, int exception_index)
 276 {
 277         if (ARM_SERROR_PENDING(exception_index)) {
 278                 if (this_cpu_has_cap(ARM64_HAS_RAS_EXTN)) {
 279                         u64 disr = kvm_vcpu_get_disr(vcpu);
 280
 281                         kvm_handle_guest_serror(vcpu, disr_to_esr(disr));
 282                 } else {
 283                         kvm_inject_vabt(vcpu);
 284                 }
 285
 286                 return;
 287         }
 288
 289         exception_index = ARM_EXCEPTION_CODE(exception_index);
 290
 291         if (exception_index == ARM_EXCEPTION_EL1_SERROR)
 292                 kvm_handle_guest_serror(vcpu, kvm_vcpu_get_esr(vcpu));
 293 }