| 1 | /* |
| 2 | * QEMU Xen emulation: Shared/overlay pages support |
| 3 | * |
| 4 | * Copyright © 2022 Amazon.com, Inc. or its affiliates. All Rights Reserved. |
| 5 | * |
| 6 | * Authors: David Woodhouse <dwmw2@infradead.org> |
| 7 | * |
| 8 | * This work is licensed under the terms of the GNU GPL, version 2 or later. |
| 9 | * See the COPYING file in the top-level directory. |
| 10 | */ |
| 11 | |
| 12 | #include "qemu/osdep.h" |
| 13 | #include "qemu/host-utils.h" |
| 14 | #include "qemu/module.h" |
| 15 | #include "qemu/main-loop.h" |
| 16 | #include "qapi/error.h" |
| 17 | #include "qom/object.h" |
| 18 | #include "exec/target_page.h" |
| 19 | #include "system/address-spaces.h" |
| 20 | #include "migration/vmstate.h" |
| 21 | |
| 22 | #include "hw/core/sysbus.h" |
| 23 | #include "hw/xen/xen.h" |
| 24 | #include "xen_overlay.h" |
| 25 | |
| 26 | #include "system/kvm.h" |
| 27 | #include "system/kvm_xen.h" |
| 28 | #include <linux/kvm.h> |
| 29 | |
| 30 | #include "hw/xen/interface/memory.h" |
| 31 | |
| 32 | |
| 33 | #define TYPE_XEN_OVERLAY "xen-overlay" |
| 34 | OBJECT_DECLARE_SIMPLE_TYPE(XenOverlayState, XEN_OVERLAY) |
| 35 | |
| 36 | #define XEN_PAGE_SHIFT 12 |
| 37 | #define XEN_PAGE_SIZE (1ULL << XEN_PAGE_SHIFT) |
| 38 | |
| 39 | struct XenOverlayState { |
| 40 | /*< private >*/ |
| 41 | SysBusDevice busdev; |
| 42 | /*< public >*/ |
| 43 | |
| 44 | MemoryRegion shinfo_mem; |
| 45 | void *shinfo_ptr; |
| 46 | uint64_t shinfo_gpa; |
| 47 | bool long_mode; |
| 48 | }; |
| 49 | |
| 50 | struct XenOverlayState *xen_overlay_singleton; |
| 51 | |
| 52 | void xen_overlay_do_map_page(MemoryRegion *page, uint64_t gpa) |
| 53 | { |
| 54 | /* |
| 55 | * Xen allows guests to map the same page as many times as it likes |
| 56 | * into guest physical frames. We don't, because it would be hard |
| 57 | * to track and restore them all. One mapping of each page is |
| 58 | * perfectly sufficient for all known guests... and we've tested |
| 59 | * that theory on a few now in other implementations. dwmw2. |
| 60 | */ |
| 61 | if (memory_region_is_mapped(page)) { |
| 62 | if (gpa == INVALID_GPA) { |
| 63 | memory_region_del_subregion(get_system_memory(), page); |
| 64 | } else { |
| 65 | /* Just move it */ |
| 66 | memory_region_set_address(page, gpa); |
| 67 | } |
| 68 | } else if (gpa != INVALID_GPA) { |
| 69 | memory_region_add_subregion_overlap(get_system_memory(), gpa, page, 0); |
| 70 | } |
| 71 | } |
| 72 | |
| 73 | /* KVM is the only existing back end for now. Let's not overengineer it yet. */ |
| 74 | static int xen_overlay_set_be_shinfo(uint64_t gfn) |
| 75 | { |
| 76 | struct kvm_xen_hvm_attr xa = { |
| 77 | .type = KVM_XEN_ATTR_TYPE_SHARED_INFO, |
| 78 | .u.shared_info.gfn = gfn, |
| 79 | }; |
| 80 | |
| 81 | return kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &xa); |
| 82 | } |
| 83 | |
| 84 | |
| 85 | static void xen_overlay_realize(DeviceState *dev, Error **errp) |
| 86 | { |
| 87 | XenOverlayState *s = XEN_OVERLAY(dev); |
| 88 | |
| 89 | if (xen_mode != XEN_EMULATE) { |
| 90 | error_setg(errp, "Xen overlay page support is for Xen emulation"); |
| 91 | return; |
| 92 | } |
| 93 | |
| 94 | memory_region_init_ram(&s->shinfo_mem, OBJECT(dev), "xen:shared_info", |
| 95 | XEN_PAGE_SIZE, &error_abort); |
| 96 | memory_region_set_enabled(&s->shinfo_mem, true); |
| 97 | |
| 98 | s->shinfo_ptr = memory_region_get_ram_ptr(&s->shinfo_mem); |
| 99 | s->shinfo_gpa = INVALID_GPA; |
| 100 | s->long_mode = false; |
| 101 | memset(s->shinfo_ptr, 0, XEN_PAGE_SIZE); |
| 102 | } |
| 103 | |
| 104 | static int xen_overlay_pre_save(void *opaque) |
| 105 | { |
| 106 | /* |
| 107 | * Fetch the kernel's idea of long_mode to avoid the race condition |
| 108 | * where the guest has set the hypercall page up in 64-bit mode but |
| 109 | * not yet made a hypercall by the time migration happens, so qemu |
| 110 | * hasn't yet noticed. |
| 111 | */ |
| 112 | return xen_sync_long_mode(); |
| 113 | } |
| 114 | |
| 115 | static int xen_overlay_post_load(void *opaque, int version_id) |
| 116 | { |
| 117 | XenOverlayState *s = opaque; |
| 118 | |
| 119 | if (s->shinfo_gpa != INVALID_GPA) { |
| 120 | xen_overlay_do_map_page(&s->shinfo_mem, s->shinfo_gpa); |
| 121 | xen_overlay_set_be_shinfo(s->shinfo_gpa >> XEN_PAGE_SHIFT); |
| 122 | } |
| 123 | if (s->long_mode) { |
| 124 | xen_set_long_mode(true); |
| 125 | } |
| 126 | |
| 127 | return 0; |
| 128 | } |
| 129 | |
| 130 | static bool xen_overlay_is_needed(void *opaque) |
| 131 | { |
| 132 | return xen_mode == XEN_EMULATE; |
| 133 | } |
| 134 | |
| 135 | static const VMStateDescription xen_overlay_vmstate = { |
| 136 | .name = "xen_overlay", |
| 137 | .version_id = 1, |
| 138 | .minimum_version_id = 1, |
| 139 | .needed = xen_overlay_is_needed, |
| 140 | .pre_save = xen_overlay_pre_save, |
| 141 | .post_load = xen_overlay_post_load, |
| 142 | .fields = (const VMStateField[]) { |
| 143 | VMSTATE_UINT64(shinfo_gpa, XenOverlayState), |
| 144 | VMSTATE_BOOL(long_mode, XenOverlayState), |
| 145 | VMSTATE_END_OF_LIST() |
| 146 | } |
| 147 | }; |
| 148 | |
| 149 | static void xen_overlay_reset(DeviceState *dev) |
| 150 | { |
| 151 | kvm_xen_soft_reset(); |
| 152 | } |
| 153 | |
| 154 | static void xen_overlay_class_init(ObjectClass *klass, const void *data) |
| 155 | { |
| 156 | DeviceClass *dc = DEVICE_CLASS(klass); |
| 157 | |
| 158 | device_class_set_legacy_reset(dc, xen_overlay_reset); |
| 159 | dc->realize = xen_overlay_realize; |
| 160 | dc->vmsd = &xen_overlay_vmstate; |
| 161 | } |
| 162 | |
| 163 | static const TypeInfo xen_overlay_info = { |
| 164 | .name = TYPE_XEN_OVERLAY, |
| 165 | .parent = TYPE_SYS_BUS_DEVICE, |
| 166 | .instance_size = sizeof(XenOverlayState), |
| 167 | .class_init = xen_overlay_class_init, |
| 168 | }; |
| 169 | |
| 170 | void xen_overlay_create(void) |
| 171 | { |
| 172 | xen_overlay_singleton = XEN_OVERLAY(sysbus_create_simple(TYPE_XEN_OVERLAY, |
| 173 | -1, NULL)); |
| 174 | |
| 175 | /* If xen_domid wasn't explicitly set, at least make sure it isn't zero. */ |
| 176 | if (xen_domid == DOMID_QEMU) { |
| 177 | xen_domid = 1; |
| 178 | }; |
| 179 | } |
| 180 | |
| 181 | static void xen_overlay_register_types(void) |
| 182 | { |
| 183 | type_register_static(&xen_overlay_info); |
| 184 | } |
| 185 | |
| 186 | type_init(xen_overlay_register_types) |
| 187 | |
| 188 | int xen_overlay_map_shinfo_page(uint64_t gpa) |
| 189 | { |
| 190 | XenOverlayState *s = xen_overlay_singleton; |
| 191 | int ret; |
| 192 | |
| 193 | if (!s) { |
| 194 | return -ENOENT; |
| 195 | } |
| 196 | |
| 197 | assert(bql_locked()); |
| 198 | |
| 199 | if (s->shinfo_gpa) { |
| 200 | /* If removing shinfo page, turn the kernel magic off first */ |
| 201 | ret = xen_overlay_set_be_shinfo(INVALID_GFN); |
| 202 | if (ret) { |
| 203 | return ret; |
| 204 | } |
| 205 | } |
| 206 | |
| 207 | xen_overlay_do_map_page(&s->shinfo_mem, gpa); |
| 208 | if (gpa != INVALID_GPA) { |
| 209 | ret = xen_overlay_set_be_shinfo(gpa >> XEN_PAGE_SHIFT); |
| 210 | if (ret) { |
| 211 | return ret; |
| 212 | } |
| 213 | } |
| 214 | s->shinfo_gpa = gpa; |
| 215 | |
| 216 | return 0; |
| 217 | } |
| 218 | |
| 219 | void *xen_overlay_get_shinfo_ptr(void) |
| 220 | { |
| 221 | XenOverlayState *s = xen_overlay_singleton; |
| 222 | |
| 223 | if (!s) { |
| 224 | return NULL; |
| 225 | } |
| 226 | |
| 227 | return s->shinfo_ptr; |
| 228 | } |
| 229 | |
| 230 | int xen_sync_long_mode(void) |
| 231 | { |
| 232 | int ret; |
| 233 | struct kvm_xen_hvm_attr xa = { |
| 234 | .type = KVM_XEN_ATTR_TYPE_LONG_MODE, |
| 235 | }; |
| 236 | |
| 237 | if (!xen_overlay_singleton) { |
| 238 | return -ENOENT; |
| 239 | } |
| 240 | |
| 241 | ret = kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_GET_ATTR, &xa); |
| 242 | if (!ret) { |
| 243 | xen_overlay_singleton->long_mode = xa.u.long_mode; |
| 244 | } |
| 245 | |
| 246 | return ret; |
| 247 | } |
| 248 | |
| 249 | int xen_set_long_mode(bool long_mode) |
| 250 | { |
| 251 | int ret; |
| 252 | struct kvm_xen_hvm_attr xa = { |
| 253 | .type = KVM_XEN_ATTR_TYPE_LONG_MODE, |
| 254 | .u.long_mode = long_mode, |
| 255 | }; |
| 256 | |
| 257 | if (!xen_overlay_singleton) { |
| 258 | return -ENOENT; |
| 259 | } |
| 260 | |
| 261 | ret = kvm_vm_ioctl(kvm_state, KVM_XEN_HVM_SET_ATTR, &xa); |
| 262 | if (!ret) { |
| 263 | xen_overlay_singleton->long_mode = xa.u.long_mode; |
| 264 | } |
| 265 | |
| 266 | return ret; |
| 267 | } |
| 268 | |
| 269 | bool xen_is_long_mode(void) |
| 270 | { |
| 271 | return xen_overlay_singleton && xen_overlay_singleton->long_mode; |
| 272 | } |