arch/x86/xen/enlighten.c

   1 // SPDX-License-Identifier: GPL-2.0
   2
   3 #ifdef CONFIG_XEN_BALLOON_MEMORY_HOTPLUG
   4 #include <linux/memblock.h>
   5 #endif
   6 #include <linux/cpu.h>
   7 #include <linux/kexec.h>
   8 #include <linux/slab.h>
   9
  10 #include <xen/xen.h>
  11 #include <xen/features.h>
  12 #include <xen/page.h>
  13
  14 #include <asm/xen/hypercall.h>
  15 #include <asm/xen/hypervisor.h>
  16 #include <asm/cpu.h>
  17 #include <asm/e820/api.h>
  18
  19 #include "xen-ops.h"
  20 #include "smp.h"
  21 #include "pmu.h"
  22
  23 EXPORT_SYMBOL_GPL(hypercall_page);
  24
  25 /*
  26  * Pointer to the xen_vcpu_info structure or
  27  * &HYPERVISOR_shared_info->vcpu_info[cpu]. See xen_hvm_init_shared_info
  28  * and xen_vcpu_setup for details. By default it points to share_info->vcpu_info
  29  * but if the hypervisor supports VCPUOP_register_vcpu_info then it can point
  30  * to xen_vcpu_info. The pointer is used in __xen_evtchn_do_upcall to
  31  * acknowledge pending events.
  32  * Also more subtly it is used by the patched version of irq enable/disable
  33  * e.g. xen_irq_enable_direct and xen_iret in PV mode.
  34  *
  35  * The desire to be able to do those mask/unmask operations as a single
  36  * instruction by using the per-cpu offset held in %gs is the real reason
  37  * vcpu info is in a per-cpu pointer and the original reason for this
  38  * hypercall.
  39  *
  40  */
  41 DEFINE_PER_CPU(struct vcpu_info *, xen_vcpu);
  42
  43 /*
  44  * Per CPU pages used if hypervisor supports VCPUOP_register_vcpu_info
  45  * hypercall. This can be used both in PV and PVHVM mode. The structure
  46  * overrides the default per_cpu(xen_vcpu, cpu) value.
  47  */
  48 DEFINE_PER_CPU(struct vcpu_info, xen_vcpu_info);
  49
  50 /* Linux <-> Xen vCPU id mapping */
  51 DEFINE_PER_CPU(uint32_t, xen_vcpu_id);
  52 EXPORT_PER_CPU_SYMBOL(xen_vcpu_id);
  53
  54 unsigned long *machine_to_phys_mapping = (void *)MACH2PHYS_VIRT_START;
  55 EXPORT_SYMBOL(machine_to_phys_mapping);
  56 unsigned long  machine_to_phys_nr;
  57 EXPORT_SYMBOL(machine_to_phys_nr);
  58
  59 struct start_info *xen_start_info;
  60 EXPORT_SYMBOL_GPL(xen_start_info);
  61
  62 struct shared_info xen_dummy_shared_info;
  63
  64 __read_mostly int xen_have_vector_callback;
  65 EXPORT_SYMBOL_GPL(xen_have_vector_callback);
  66
  67 /*
  68  * NB: These need to live in .data or alike because they're used by
  69  * xen_prepare_pvh() which runs before clearing the bss.
  70  */
  71 enum xen_domain_type __ro_after_init xen_domain_type = XEN_NATIVE;
  72 EXPORT_SYMBOL_GPL(xen_domain_type);
  73 uint32_t xen_start_flags __section(".data") = 0;
  74 EXPORT_SYMBOL(xen_start_flags);
  75
  76 /*
  77  * Point at some empty memory to start with. We map the real shared_info
  78  * page as soon as fixmap is up and running.
  79  */
  80 struct shared_info *HYPERVISOR_shared_info = &xen_dummy_shared_info;
  81
  82 /*
  83  * Flag to determine whether vcpu info placement is available on all
  84  * VCPUs.  We assume it is to start with, and then set it to zero on
  85  * the first failure.  This is because it can succeed on some VCPUs
  86  * and not others, since it can involve hypervisor memory allocation,
  87  * or because the guest failed to guarantee all the appropriate
  88  * constraints on all VCPUs (ie buffer can't cross a page boundary).
  89  *
  90  * Note that any particular CPU may be using a placed vcpu structure,
  91  * but we can only optimise if the all are.
  92  *
  93  * 0: not available, 1: available
  94  */
  95 int xen_have_vcpu_info_placement = 1;
  96
  97 static int xen_cpu_up_online(unsigned int cpu)
  98 {
  99         xen_init_lock_cpu(cpu);
 100         return 0;
 101 }
 102
 103 int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned int),
 104                     int (*cpu_dead_cb)(unsigned int))
 105 {
 106         int rc;
 107
 108         rc = cpuhp_setup_state_nocalls(CPUHP_XEN_PREPARE,
 109                                        "x86/xen/guest:prepare",
 110                                        cpu_up_prepare_cb, cpu_dead_cb);
 111         if (rc >= 0) {
 112                 rc = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
 113                                                "x86/xen/guest:online",
 114                                                xen_cpu_up_online, NULL);
 115                 if (rc < 0)
 116                         cpuhp_remove_state_nocalls(CPUHP_XEN_PREPARE);
 117         }
 118
 119         return rc >= 0 ? 0 : rc;
 120 }
 121
 122 static int xen_vcpu_setup_restore(int cpu)
 123 {
 124         int rc = 0;
 125
 126         /* Any per_cpu(xen_vcpu) is stale, so reset it */
 127         xen_vcpu_info_reset(cpu);
 128
 129         /*
 130          * For PVH and PVHVM, setup online VCPUs only. The rest will
 131          * be handled by hotplug.
 132          */
 133         if (xen_pv_domain() ||
 134             (xen_hvm_domain() && cpu_online(cpu))) {
 135                 rc = xen_vcpu_setup(cpu);
 136         }
 137
 138         return rc;
 139 }
 140
 141 /*
 142  * On restore, set the vcpu placement up again.
 143  * If it fails, then we're in a bad state, since
 144  * we can't back out from using it...
 145  */
 146 void xen_vcpu_restore(void)
 147 {
 148         int cpu, rc;
 149
 150         for_each_possible_cpu(cpu) {
 151                 bool other_cpu = (cpu != smp_processor_id());
 152                 bool is_up;
 153
 154                 if (xen_vcpu_nr(cpu) == XEN_VCPU_ID_INVALID)
 155                         continue;
 156
 157                 /* Only Xen 4.5 and higher support this. */
 158                 is_up = HYPERVISOR_vcpu_op(VCPUOP_is_up,
 159                                            xen_vcpu_nr(cpu), NULL) > 0;
 160
 161                 if (other_cpu && is_up &&
 162                     HYPERVISOR_vcpu_op(VCPUOP_down, xen_vcpu_nr(cpu), NULL))
 163                         BUG();
 164
 165                 if (xen_pv_domain() || xen_feature(XENFEAT_hvm_safe_pvclock))
 166                         xen_setup_runstate_info(cpu);
 167
 168                 rc = xen_vcpu_setup_restore(cpu);
 169                 if (rc)
 170                         pr_emerg_once("vcpu restore failed for cpu=%d err=%d. "
 171                                         "System will hang.\n", cpu, rc);
 172                 /*
 173                  * In case xen_vcpu_setup_restore() fails, do not bring up the
 174                  * VCPU. This helps us avoid the resulting OOPS when the VCPU
 175                  * accesses pvclock_vcpu_time via xen_vcpu (which is NULL.)
 176                  * Note that this does not improve the situation much -- now the
 177                  * VM hangs instead of OOPSing -- with the VCPUs that did not
 178                  * fail, spinning in stop_machine(), waiting for the failed
 179                  * VCPUs to come up.
 180                  */
 181                 if (other_cpu && is_up && (rc == 0) &&
 182                     HYPERVISOR_vcpu_op(VCPUOP_up, xen_vcpu_nr(cpu), NULL))
 183                         BUG();
 184         }
 185 }
 186
 187 void xen_vcpu_info_reset(int cpu)
 188 {
 189         if (xen_vcpu_nr(cpu) < MAX_VIRT_CPUS) {
 190                 per_cpu(xen_vcpu, cpu) =
 191                         &HYPERVISOR_shared_info->vcpu_info[xen_vcpu_nr(cpu)];
 192         } else {
 193                 /* Set to NULL so that if somebody accesses it we get an OOPS */
 194                 per_cpu(xen_vcpu, cpu) = NULL;
 195         }
 196 }
 197
 198 int xen_vcpu_setup(int cpu)
 199 {
 200         struct vcpu_register_vcpu_info info;
 201         int err;
 202         struct vcpu_info *vcpup;
 203
 204         BUG_ON(HYPERVISOR_shared_info == &xen_dummy_shared_info);
 205
 206         /*
 207          * This path is called on PVHVM at bootup (xen_hvm_smp_prepare_boot_cpu)
 208          * and at restore (xen_vcpu_restore). Also called for hotplugged
 209          * VCPUs (cpu_init -> xen_hvm_cpu_prepare_hvm).
 210          * However, the hypercall can only be done once (see below) so if a VCPU
 211          * is offlined and comes back online then let's not redo the hypercall.
 212          *
 213          * For PV it is called during restore (xen_vcpu_restore) and bootup
 214          * (xen_setup_vcpu_info_placement). The hotplug mechanism does not
 215          * use this function.
 216          */
 217         if (xen_hvm_domain()) {
 218                 if (per_cpu(xen_vcpu, cpu) == &per_cpu(xen_vcpu_info, cpu))
 219                         return 0;
 220         }
 221
 222         if (xen_have_vcpu_info_placement) {
 223                 vcpup = &per_cpu(xen_vcpu_info, cpu);
 224                 info.mfn = arbitrary_virt_to_mfn(vcpup);
 225                 info.offset = offset_in_page(vcpup);
 226
 227                 /*
 228                  * Check to see if the hypervisor will put the vcpu_info
 229                  * structure where we want it, which allows direct access via
 230                  * a percpu-variable.
 231                  * N.B. This hypercall can _only_ be called once per CPU.
 232                  * Subsequent calls will error out with -EINVAL. This is due to
 233                  * the fact that hypervisor has no unregister variant and this
 234                  * hypercall does not allow to over-write info.mfn and
 235                  * info.offset.
 236                  */
 237                 err = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_info,
 238                                          xen_vcpu_nr(cpu), &info);
 239
 240                 if (err) {
 241                         pr_warn_once("register_vcpu_info failed: cpu=%d err=%d\n",
 242                                      cpu, err);
 243                         xen_have_vcpu_info_placement = 0;
 244                 } else {
 245                         /*
 246                          * This cpu is using the registered vcpu info, even if
 247                          * later ones fail to.
 248                          */
 249                         per_cpu(xen_vcpu, cpu) = vcpup;
 250                 }
 251         }
 252
 253         if (!xen_have_vcpu_info_placement)
 254                 xen_vcpu_info_reset(cpu);
 255
 256         return ((per_cpu(xen_vcpu, cpu) == NULL) ? -ENODEV : 0);
 257 }
 258
 259 void xen_reboot(int reason)
 260 {
 261         struct sched_shutdown r = { .reason = reason };
 262         int cpu;
 263
 264         for_each_online_cpu(cpu)
 265                 xen_pmu_finish(cpu);
 266
 267         if (HYPERVISOR_sched_op(SCHEDOP_shutdown, &r))
 268                 BUG();
 269 }
 270
 271 static int reboot_reason = SHUTDOWN_reboot;
 272 static bool xen_legacy_crash;
 273 void xen_emergency_restart(void)
 274 {
 275         xen_reboot(reboot_reason);
 276 }
 277
 278 static int
 279 xen_panic_event(struct notifier_block *this, unsigned long event, void *ptr)
 280 {
 281         if (!kexec_crash_loaded()) {
 282                 if (xen_legacy_crash)
 283                         xen_reboot(SHUTDOWN_crash);
 284
 285                 reboot_reason = SHUTDOWN_crash;
 286
 287                 /*
 288                  * If panic_timeout==0 then we are supposed to wait forever.
 289                  * However, to preserve original dom0 behavior we have to drop
 290                  * into hypervisor. (domU behavior is controlled by its
 291                  * config file)
 292                  */
 293                 if (panic_timeout == 0)
 294                         panic_timeout = -1;
 295         }
 296         return NOTIFY_DONE;
 297 }
 298
 299 static int __init parse_xen_legacy_crash(char *arg)
 300 {
 301         xen_legacy_crash = true;
 302         return 0;
 303 }
 304 early_param("xen_legacy_crash", parse_xen_legacy_crash);
 305
 306 static struct notifier_block xen_panic_block = {
 307         .notifier_call = xen_panic_event,
 308         .priority = INT_MIN
 309 };
 310
 311 int xen_panic_handler_init(void)
 312 {
 313         atomic_notifier_chain_register(&panic_notifier_list, &xen_panic_block);
 314         return 0;
 315 }
 316
 317 void xen_pin_vcpu(int cpu)
 318 {
 319         static bool disable_pinning;
 320         struct sched_pin_override pin_override;
 321         int ret;
 322
 323         if (disable_pinning)
 324                 return;
 325
 326         pin_override.pcpu = cpu;
 327         ret = HYPERVISOR_sched_op(SCHEDOP_pin_override, &pin_override);
 328
 329         /* Ignore errors when removing override. */
 330         if (cpu < 0)
 331                 return;
 332
 333         switch (ret) {
 334         case -ENOSYS:
 335                 pr_warn("Unable to pin on physical cpu %d. In case of problems consider vcpu pinning.\n",
 336                         cpu);
 337                 disable_pinning = true;
 338                 break;
 339         case -EPERM:
 340                 WARN(1, "Trying to pin vcpu without having privilege to do so\n");
 341                 disable_pinning = true;
 342                 break;
 343         case -EINVAL:
 344         case -EBUSY:
 345                 pr_warn("Physical cpu %d not available for pinning. Check Xen cpu configuration.\n",
 346                         cpu);
 347                 break;
 348         case 0:
 349                 break;
 350         default:
 351                 WARN(1, "rc %d while trying to pin vcpu\n", ret);
 352                 disable_pinning = true;
 353         }
 354 }
 355
 356 #ifdef CONFIG_HOTPLUG_CPU
 357 void xen_arch_register_cpu(int num)
 358 {
 359         arch_register_cpu(num);
 360 }
 361 EXPORT_SYMBOL(xen_arch_register_cpu);
 362
 363 void xen_arch_unregister_cpu(int num)
 364 {
 365         arch_unregister_cpu(num);
 366 }
 367 EXPORT_SYMBOL(xen_arch_unregister_cpu);
 368 #endif