xref: /freebsd/sys/x86/xen/pv.c (revision 78b9f0095b4af3aca6c931b2c7b009ddb8a05125)
1 /*-
2  * SPDX-License-Identifier: BSD-2-Clause-NetBSD
3  *
4  * Copyright (c) 2004 Christian Limpach.
5  * Copyright (c) 2004-2006,2008 Kip Macy
6  * Copyright (c) 2008 The NetBSD Foundation, Inc.
7  * Copyright (c) 2013 Roger Pau Monné <roger.pau@citrix.com>
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  *
19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS AS IS'' AND
20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
23  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
24  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
25  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
26  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
27  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
28  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
29  * SUCH DAMAGE.
30  */
31 
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34 
35 #include "opt_ddb.h"
36 #include "opt_kstack_pages.h"
37 
38 #include <sys/param.h>
39 #include <sys/bus.h>
40 #include <sys/kernel.h>
41 #include <sys/reboot.h>
42 #include <sys/systm.h>
43 #include <sys/malloc.h>
44 #include <sys/linker.h>
45 #include <sys/lock.h>
46 #include <sys/rwlock.h>
47 #include <sys/boot.h>
48 #include <sys/ctype.h>
49 #include <sys/mutex.h>
50 #include <sys/smp.h>
51 
52 #include <vm/vm.h>
53 #include <vm/vm_extern.h>
54 #include <vm/vm_kern.h>
55 #include <vm/vm_page.h>
56 #include <vm/vm_map.h>
57 #include <vm/vm_object.h>
58 #include <vm/vm_pager.h>
59 #include <vm/vm_param.h>
60 
61 #include <machine/_inttypes.h>
62 #include <machine/intr_machdep.h>
63 #include <x86/apicvar.h>
64 #include <x86/init.h>
65 #include <machine/pc/bios.h>
66 #include <machine/smp.h>
67 #include <machine/intr_machdep.h>
68 #include <machine/metadata.h>
69 
70 #include <xen/xen-os.h>
71 #include <xen/hvm.h>
72 #include <xen/hypervisor.h>
73 #include <xen/xenstore/xenstorevar.h>
74 #include <xen/xen_pv.h>
75 #include <xen/xen_msi.h>
76 
77 #include <xen/interface/arch-x86/hvm/start_info.h>
78 #include <xen/interface/vcpu.h>
79 
80 #include <dev/xen/timer/timer.h>
81 
82 #ifdef DDB
83 #include <ddb/ddb.h>
84 #endif
85 
86 /* Native initial function */
87 extern u_int64_t hammer_time(u_int64_t, u_int64_t);
88 /* Xen initial function */
89 uint64_t hammer_time_xen_legacy(start_info_t *, uint64_t);
90 uint64_t hammer_time_xen(vm_paddr_t);
91 
92 #define MAX_E820_ENTRIES	128
93 
94 /*--------------------------- Forward Declarations ---------------------------*/
95 static caddr_t xen_legacy_pvh_parse_preload_data(uint64_t);
96 static caddr_t xen_pvh_parse_preload_data(uint64_t);
97 static void xen_pvh_parse_memmap(caddr_t, vm_paddr_t *, int *);
98 
99 #ifdef SMP
100 static int xen_pv_start_all_aps(void);
101 #endif
102 
103 /*---------------------------- Extern Declarations ---------------------------*/
104 #ifdef SMP
105 /* Variables used by amd64 mp_machdep to start APs */
106 extern char *doublefault_stack;
107 extern char *mce_stack;
108 extern char *nmi_stack;
109 extern char *dbg_stack;
110 #endif
111 
112 /*
113  * Placed by the linker at the end of the bss section, which is the last
114  * section loaded by Xen before loading the symtab and strtab.
115  */
116 extern uint32_t end;
117 
118 /*-------------------------------- Global Data -------------------------------*/
119 /* Xen init_ops implementation. */
120 struct init_ops xen_legacy_init_ops = {
121 	.parse_preload_data		= xen_legacy_pvh_parse_preload_data,
122 	.early_clock_source_init	= xen_clock_init,
123 	.early_delay			= xen_delay,
124 	.parse_memmap			= xen_pvh_parse_memmap,
125 #ifdef SMP
126 	.start_all_aps			= xen_pv_start_all_aps,
127 #endif
128 	.msi_init			= xen_msi_init,
129 };
130 
131 struct init_ops xen_pvh_init_ops = {
132 	.parse_preload_data		= xen_pvh_parse_preload_data,
133 	.early_clock_source_init	= xen_clock_init,
134 	.early_delay			= xen_delay,
135 	.parse_memmap			= xen_pvh_parse_memmap,
136 #ifdef SMP
137 	.mp_bootaddress			= mp_bootaddress,
138 	.start_all_aps			= native_start_all_aps,
139 #endif
140 	.msi_init			= msi_init,
141 };
142 
143 static struct bios_smap xen_smap[MAX_E820_ENTRIES];
144 
145 static start_info_t *legacy_start_info;
146 static struct hvm_start_info *start_info;
147 
148 /*----------------------- Legacy PVH start_info accessors --------------------*/
149 static vm_paddr_t
150 legacy_get_xenstore_mfn(void)
151 {
152 
153 	return (legacy_start_info->store_mfn);
154 }
155 
156 static evtchn_port_t
157 legacy_get_xenstore_evtchn(void)
158 {
159 
160 	return (legacy_start_info->store_evtchn);
161 }
162 
163 static vm_paddr_t
164 legacy_get_console_mfn(void)
165 {
166 
167 	return (legacy_start_info->console.domU.mfn);
168 }
169 
170 static evtchn_port_t
171 legacy_get_console_evtchn(void)
172 {
173 
174 	return (legacy_start_info->console.domU.evtchn);
175 }
176 
177 static uint32_t
178 legacy_get_start_flags(void)
179 {
180 
181 	return (legacy_start_info->flags);
182 }
183 
184 struct hypervisor_info legacy_info = {
185 	.get_xenstore_mfn		= legacy_get_xenstore_mfn,
186 	.get_xenstore_evtchn		= legacy_get_xenstore_evtchn,
187 	.get_console_mfn		= legacy_get_console_mfn,
188 	.get_console_evtchn		= legacy_get_console_evtchn,
189 	.get_start_flags		= legacy_get_start_flags,
190 };
191 
192 /*-------------------------------- Xen PV init -------------------------------*/
193 /*
194  * First function called by the Xen legacy PVH boot sequence.
195  *
196  * Set some Xen global variables and prepare the environment so it is
197  * as similar as possible to what native FreeBSD init function expects.
198  */
199 uint64_t
200 hammer_time_xen_legacy(start_info_t *si, uint64_t xenstack)
201 {
202 	uint64_t physfree;
203 	uint64_t *PT4 = (u_int64_t *)xenstack;
204 	uint64_t *PT3 = (u_int64_t *)(xenstack + PAGE_SIZE);
205 	uint64_t *PT2 = (u_int64_t *)(xenstack + 2 * PAGE_SIZE);
206 	int i;
207 
208 	xen_domain_type = XEN_PV_DOMAIN;
209 	vm_guest = VM_GUEST_XEN;
210 
211 	if ((si == NULL) || (xenstack == 0)) {
212 		xc_printf("ERROR: invalid start_info or xen stack, halting\n");
213 		HYPERVISOR_shutdown(SHUTDOWN_crash);
214 	}
215 
216 	xc_printf("FreeBSD PVH running on %s\n", si->magic);
217 
218 	/* We use 3 pages of xen stack for the boot pagetables */
219 	physfree = xenstack + 3 * PAGE_SIZE - KERNBASE;
220 
221 	/* Setup Xen global variables */
222 	legacy_start_info = si;
223 	HYPERVISOR_shared_info =
224 	    (shared_info_t *)(si->shared_info + KERNBASE);
225 
226 	/*
227 	 * Use the stack Xen gives us to build the page tables
228 	 * as native FreeBSD expects to find them (created
229 	 * by the boot trampoline).
230 	 */
231 	for (i = 0; i < (PAGE_SIZE / sizeof(uint64_t)); i++) {
232 		/*
233 		 * Each slot of the level 4 pages points
234 		 * to the same level 3 page
235 		 */
236 		PT4[i] = ((uint64_t)&PT3[0]) - KERNBASE;
237 		PT4[i] |= PG_V | PG_RW | PG_U;
238 
239 		/*
240 		 * Each slot of the level 3 pages points
241 		 * to the same level 2 page
242 		 */
243 		PT3[i] = ((uint64_t)&PT2[0]) - KERNBASE;
244 		PT3[i] |= PG_V | PG_RW | PG_U;
245 
246 		/*
247 		 * The level 2 page slots are mapped with
248 		 * 2MB pages for 1GB.
249 		 */
250 		PT2[i] = i * (2 * 1024 * 1024);
251 		PT2[i] |= PG_V | PG_RW | PG_PS | PG_U;
252 	}
253 	load_cr3(((uint64_t)&PT4[0]) - KERNBASE);
254 
255 	/* Set the hooks for early functions that diverge from bare metal */
256 	init_ops = xen_legacy_init_ops;
257 	apic_ops = xen_apic_ops;
258 	hypervisor_info = legacy_info;
259 
260 	/* Now we can jump into the native init function */
261 	return (hammer_time(0, physfree));
262 }
263 
264 uint64_t
265 hammer_time_xen(vm_paddr_t start_info_paddr)
266 {
267 	struct hvm_modlist_entry *mod;
268 	struct xen_add_to_physmap xatp;
269 	uint64_t physfree;
270 	char *kenv;
271 	int rc;
272 
273 	xen_domain_type = XEN_HVM_DOMAIN;
274 	vm_guest = VM_GUEST_XEN;
275 
276 	rc = xen_hvm_init_hypercall_stubs(XEN_HVM_INIT_EARLY);
277 	if (rc) {
278 		xc_printf("ERROR: failed to initialize hypercall page: %d\n",
279 		    rc);
280 		HYPERVISOR_shutdown(SHUTDOWN_crash);
281 	}
282 
283 	start_info = (struct hvm_start_info *)(start_info_paddr + KERNBASE);
284 	if (start_info->magic != XEN_HVM_START_MAGIC_VALUE) {
285 		xc_printf("Unknown magic value in start_info struct: %#x\n",
286 		    start_info->magic);
287 		HYPERVISOR_shutdown(SHUTDOWN_crash);
288 	}
289 
290 	/*
291 	 * The hvm_start_into structure is always appended after loading
292 	 * the kernel and modules.
293 	 */
294 	physfree = roundup2(start_info_paddr + PAGE_SIZE, PAGE_SIZE);
295 
296 	xatp.domid = DOMID_SELF;
297 	xatp.idx = 0;
298 	xatp.space = XENMAPSPACE_shared_info;
299 	xatp.gpfn = atop(physfree);
300 	if (HYPERVISOR_memory_op(XENMEM_add_to_physmap, &xatp)) {
301 		xc_printf("ERROR: failed to setup shared_info page\n");
302 		HYPERVISOR_shutdown(SHUTDOWN_crash);
303 	}
304 	HYPERVISOR_shared_info = (shared_info_t *)(physfree + KERNBASE);
305 	physfree += PAGE_SIZE;
306 
307 	/*
308 	 * Init a static kenv using a free page. The contents will be filled
309 	 * from the parse_preload_data hook.
310 	 */
311 	kenv = (void *)(physfree + KERNBASE);
312 	physfree += PAGE_SIZE;
313 	bzero(kenv, PAGE_SIZE);
314 	init_static_kenv(kenv, PAGE_SIZE);
315 
316 	if (start_info->modlist_paddr != 0) {
317 		if (start_info->modlist_paddr >= physfree) {
318 			xc_printf(
319 			    "ERROR: unexpected module list memory address\n");
320 			HYPERVISOR_shutdown(SHUTDOWN_crash);
321 		}
322 		if (start_info->nr_modules == 0) {
323 			xc_printf(
324 			    "ERROR: modlist_paddr != 0 but nr_modules == 0\n");
325 			HYPERVISOR_shutdown(SHUTDOWN_crash);
326 		}
327 		mod = (struct hvm_modlist_entry *)
328 		    (vm_paddr_t)start_info->modlist_paddr + KERNBASE;
329 		if (mod[0].paddr >= physfree) {
330 			xc_printf("ERROR: unexpected module memory address\n");
331 			HYPERVISOR_shutdown(SHUTDOWN_crash);
332 		}
333 	}
334 
335 	/* Set the hooks for early functions that diverge from bare metal */
336 	init_ops = xen_pvh_init_ops;
337 	hvm_start_flags = start_info->flags;
338 
339 	/* Now we can jump into the native init function */
340 	return (hammer_time(0, physfree));
341 }
342 
343 /*-------------------------------- PV specific -------------------------------*/
344 #ifdef SMP
345 static bool
346 start_xen_ap(int cpu)
347 {
348 	struct vcpu_guest_context *ctxt;
349 	int ms, cpus = mp_naps;
350 	const size_t stacksize = kstack_pages * PAGE_SIZE;
351 
352 	/* allocate and set up an idle stack data page */
353 	bootstacks[cpu] =
354 	    (void *)kmem_malloc(kernel_arena, stacksize, M_WAITOK | M_ZERO);
355 	doublefault_stack =
356 	    (char *)kmem_malloc(kernel_arena, PAGE_SIZE, M_WAITOK | M_ZERO);
357 	mce_stack =
358 	    (char *)kmem_malloc(kernel_arena, PAGE_SIZE, M_WAITOK | M_ZERO);
359 	nmi_stack =
360 	    (char *)kmem_malloc(kernel_arena, PAGE_SIZE, M_WAITOK | M_ZERO);
361 	dbg_stack =
362 	    (void *)kmem_malloc(kernel_arena, PAGE_SIZE, M_WAITOK | M_ZERO);
363 	dpcpu =
364 	    (void *)kmem_malloc(kernel_arena, DPCPU_SIZE, M_WAITOK | M_ZERO);
365 
366 	bootSTK = (char *)bootstacks[cpu] + kstack_pages * PAGE_SIZE - 8;
367 	bootAP = cpu;
368 
369 	ctxt = malloc(sizeof(*ctxt), M_TEMP, M_WAITOK | M_ZERO);
370 
371 	ctxt->flags = VGCF_IN_KERNEL;
372 	ctxt->user_regs.rip = (unsigned long) init_secondary;
373 	ctxt->user_regs.rsp = (unsigned long) bootSTK;
374 
375 	/* Set the AP to use the same page tables */
376 	ctxt->ctrlreg[3] = KPML4phys;
377 
378 	if (HYPERVISOR_vcpu_op(VCPUOP_initialise, cpu, ctxt))
379 		panic("unable to initialize AP#%d", cpu);
380 
381 	free(ctxt, M_TEMP);
382 
383 	/* Launch the vCPU */
384 	if (HYPERVISOR_vcpu_op(VCPUOP_up, cpu, NULL))
385 		panic("unable to start AP#%d", cpu);
386 
387 	/* Wait up to 5 seconds for it to start. */
388 	for (ms = 0; ms < 5000; ms++) {
389 		if (mp_naps > cpus)
390 			return (true);
391 		DELAY(1000);
392 	}
393 
394 	return (false);
395 }
396 
397 static int
398 xen_pv_start_all_aps(void)
399 {
400 	int cpu;
401 
402 	mtx_init(&ap_boot_mtx, "ap boot", NULL, MTX_SPIN);
403 
404 	for (cpu = 1; cpu < mp_ncpus; cpu++) {
405 
406 		/* attempt to start the Application Processor */
407 		if (!start_xen_ap(cpu))
408 			panic("AP #%d failed to start!", cpu);
409 
410 		CPU_SET(cpu, &all_cpus);	/* record AP in CPU map */
411 	}
412 
413 	return (mp_naps);
414 }
415 #endif /* SMP */
416 
417 /*
418  * When booted as a PVH guest FreeBSD needs to avoid using the RSDP address
419  * hint provided by the loader because it points to the native set of ACPI
420  * tables instead of the ones crafted by Xen. The acpi.rsdp env variable is
421  * removed from kenv if present, and a new acpi.rsdp is added to kenv that
422  * points to the address of the Xen crafted RSDP.
423  */
424 static bool reject_option(const char *option)
425 {
426 	static const char *reject[] = {
427 		"acpi.rsdp",
428 	};
429 	unsigned int i;
430 
431 	for (i = 0; i < nitems(reject); i++)
432 		if (strncmp(option, reject[i], strlen(reject[i])) == 0)
433 			return (true);
434 
435 	return (false);
436 }
437 
438 static void
439 xen_pvh_set_env(char *env, bool (*filter)(const char *))
440 {
441 	char *option;
442 
443 	if (env == NULL)
444 		return;
445 
446 	option = env;
447 	while (*option != 0) {
448 		char *value;
449 
450 		if (filter != NULL && filter(option)) {
451 			option += strlen(option) + 1;
452 			continue;
453 		}
454 
455 		value = option;
456 		option = strsep(&value, "=");
457 		if (kern_setenv(option, value) != 0)
458 			xc_printf("unable to add kenv %s=%s\n", option, value);
459 		option = value + strlen(value) + 1;
460 	}
461 }
462 
463 #ifdef DDB
464 /*
465  * The way Xen loads the symtab is different from the native boot loader,
466  * because it's tailored for NetBSD. So we have to adapt and use the same
467  * method as NetBSD. Portions of the code below have been picked from NetBSD:
468  * sys/kern/kern_ksyms.c CVS Revision 1.71.
469  */
470 static void
471 xen_pvh_parse_symtab(void)
472 {
473 	Elf_Ehdr *ehdr;
474 	Elf_Shdr *shdr;
475 	uint32_t size;
476 	int i, j;
477 
478 	size = end;
479 
480 	ehdr = (Elf_Ehdr *)(&end + 1);
481 	if (memcmp(ehdr->e_ident, ELFMAG, SELFMAG) ||
482 	    ehdr->e_ident[EI_CLASS] != ELF_TARG_CLASS ||
483 	    ehdr->e_version > 1) {
484 		xc_printf("Unable to load ELF symtab: invalid symbol table\n");
485 		return;
486 	}
487 
488 	shdr = (Elf_Shdr *)((uint8_t *)ehdr + ehdr->e_shoff);
489 	/* Find the symbol table and the corresponding string table. */
490 	for (i = 1; i < ehdr->e_shnum; i++) {
491 		if (shdr[i].sh_type != SHT_SYMTAB)
492 			continue;
493 		if (shdr[i].sh_offset == 0)
494 			continue;
495 		ksymtab = (uintptr_t)((uint8_t *)ehdr + shdr[i].sh_offset);
496 		ksymtab_size = shdr[i].sh_size;
497 		j = shdr[i].sh_link;
498 		if (shdr[j].sh_offset == 0)
499 			continue; /* Can this happen? */
500 		kstrtab = (uintptr_t)((uint8_t *)ehdr + shdr[j].sh_offset);
501 		break;
502 	}
503 
504 	if (ksymtab == 0 || kstrtab == 0)
505 		xc_printf(
506     "Unable to load ELF symtab: could not find symtab or strtab\n");
507 }
508 #endif
509 
510 static caddr_t
511 xen_legacy_pvh_parse_preload_data(uint64_t modulep)
512 {
513 	caddr_t		 kmdp;
514 	vm_ooffset_t	 off;
515 	vm_paddr_t	 metadata;
516 	char             *envp;
517 
518 	if (legacy_start_info->mod_start != 0) {
519 		preload_metadata = (caddr_t)legacy_start_info->mod_start;
520 
521 		kmdp = preload_search_by_type("elf kernel");
522 		if (kmdp == NULL)
523 			kmdp = preload_search_by_type("elf64 kernel");
524 		KASSERT(kmdp != NULL, ("unable to find kernel"));
525 
526 		/*
527 		 * Xen has relocated the metadata and the modules,
528 		 * so we need to recalculate it's position. This is
529 		 * done by saving the original modulep address and
530 		 * then calculating the offset with mod_start,
531 		 * which contains the relocated modulep address.
532 		 */
533 		metadata = MD_FETCH(kmdp, MODINFOMD_MODULEP, vm_paddr_t);
534 		off = legacy_start_info->mod_start - metadata;
535 
536 		preload_bootstrap_relocate(off);
537 
538 		boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
539 		envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
540 		if (envp != NULL)
541 			envp += off;
542 		xen_pvh_set_env(envp, NULL);
543 	} else {
544 		/* Parse the extra boot information given by Xen */
545 		boot_parse_cmdline_delim(legacy_start_info->cmd_line, ",");
546 		kmdp = NULL;
547 	}
548 
549 	boothowto |= boot_env_to_howto();
550 
551 #ifdef DDB
552 	xen_pvh_parse_symtab();
553 #endif
554 	return (kmdp);
555 }
556 
557 static caddr_t
558 xen_pvh_parse_preload_data(uint64_t modulep)
559 {
560 	caddr_t kmdp;
561 	vm_ooffset_t off;
562 	vm_paddr_t metadata;
563 	char *envp;
564 	char acpi_rsdp[19];
565 
566 	if (start_info->modlist_paddr != 0) {
567 		struct hvm_modlist_entry *mod;
568 
569 		mod = (struct hvm_modlist_entry *)
570 		    (start_info->modlist_paddr + KERNBASE);
571 		preload_metadata = (caddr_t)(mod[0].paddr + KERNBASE);
572 
573 		kmdp = preload_search_by_type("elf kernel");
574 		if (kmdp == NULL)
575 			kmdp = preload_search_by_type("elf64 kernel");
576 		KASSERT(kmdp != NULL, ("unable to find kernel"));
577 
578 		/*
579 		 * Xen has relocated the metadata and the modules,
580 		 * so we need to recalculate it's position. This is
581 		 * done by saving the original modulep address and
582 		 * then calculating the offset with mod_start,
583 		 * which contains the relocated modulep address.
584 		 */
585 		metadata = MD_FETCH(kmdp, MODINFOMD_MODULEP, vm_paddr_t);
586 		off = mod[0].paddr + KERNBASE - metadata;
587 
588 		preload_bootstrap_relocate(off);
589 
590 		boothowto = MD_FETCH(kmdp, MODINFOMD_HOWTO, int);
591 		envp = MD_FETCH(kmdp, MODINFOMD_ENVP, char *);
592 		if (envp != NULL)
593 			envp += off;
594 		xen_pvh_set_env(envp, reject_option);
595 	} else {
596 		/* Parse the extra boot information given by Xen */
597 		if (start_info->cmdline_paddr != 0)
598 			boot_parse_cmdline_delim(
599 			    (char *)(start_info->cmdline_paddr + KERNBASE),
600 			    ",");
601 		kmdp = NULL;
602 	}
603 
604 	boothowto |= boot_env_to_howto();
605 
606 	snprintf(acpi_rsdp, sizeof(acpi_rsdp), "%#" PRIx64,
607 	    start_info->rsdp_paddr);
608 	kern_setenv("acpi.rsdp", acpi_rsdp);
609 
610 #ifdef DDB
611 	xen_pvh_parse_symtab();
612 #endif
613 	return (kmdp);
614 }
615 
616 static void
617 xen_pvh_parse_memmap(caddr_t kmdp, vm_paddr_t *physmap, int *physmap_idx)
618 {
619 	struct xen_memory_map memmap;
620 	u_int32_t size;
621 	int rc;
622 
623 	/* Fetch the E820 map from Xen */
624 	memmap.nr_entries = MAX_E820_ENTRIES;
625 	set_xen_guest_handle(memmap.buffer, xen_smap);
626 	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
627 	if (rc) {
628 		xc_printf("ERROR: unable to fetch Xen E820 memory map: %d\n",
629 		    rc);
630 		HYPERVISOR_shutdown(SHUTDOWN_crash);
631 	}
632 
633 	size = memmap.nr_entries * sizeof(xen_smap[0]);
634 
635 	bios_add_smap_entries(xen_smap, size, physmap, physmap_idx);
636 }
637