xen: implement hook to fetch and parse e820 memory map

e820 memory map is fetched using a hypercall under Xen PVH, so add a
hook to init_ops in oder to diverge from bare metal and implement a
Xen variant.

Approved by: gibbs
Sponsored by: Citrix Systems R&D

x86/include/init.h:
 - Add a parse_memmap hook to init_ops, that will be called to fetch
   and parse the memory map.

amd64/amd64/machdep.c:
 - Decouple the fetch and the parse of the memmap, so the parse
   function can be shared with Xen code.
 - Move code around in order to implement the parse_memmap hook.

amd64/include/pc/bios.h:
 - Declare bios_add_smap_entries (implemented in machdep.c).

x86/xen/pv.c:
 - Implement fetching of e820 memmap when running as a PVH guest by
   using the XENMEM_memory_map hypercall.

sys/amd64/amd64/machdep.c

@@ -169,11 +169,15 @@ SYSINIT(cpu, SI_SUB_CPU, SI_ORDER_FIRST, cpu_startup, NULL);
 /* Preload data parse function */
 static caddr_t native_parse_preload_data(u_int64_t);
 
+/* Native function to fetch and parse the e820 map */
+static void native_parse_memmap(caddr_t, vm_paddr_t *, int *);
+
 /* Default init_ops implementation. */
 struct init_ops init_ops = {
 	.parse_preload_data =	native_parse_preload_data,
 	.early_clock_source_init =	i8254_init,
 	.early_delay =			i8254_delay,
+	.parse_memmap =			native_parse_memmap,
 };
 
 /*
@@ -1403,21 +1407,12 @@ add_physmap_entry(uint64_t base, uint64_t length, vm_paddr_t *physmap,
 	return (1);
 }
 
-static void
-add_smap_entries(struct bios_smap *smapbase, vm_paddr_t *physmap,
-    int *physmap_idx)
+void
+bios_add_smap_entries(struct bios_smap *smapbase, u_int32_t smapsize,
+                      vm_paddr_t *physmap, int *physmap_idx)
 {
 	struct bios_smap *smap, *smapend;
-	u_int32_t smapsize;
 
-	/*
-	 * Memory map from INT 15:E820.
-	 *
-	 * subr_module.c says:
-	 * "Consumer may safely assume that size value precedes data."
-	 * ie: an int32_t immediately precedes smap.
-	 */
-	smapsize = *((u_int32_t *)smapbase - 1);
 	smapend = (struct bios_smap *)((uintptr_t)smapbase + smapsize);
 
 	for (smap = smapbase; smap < smapend; smap++) {
@@ -1434,6 +1429,29 @@ add_smap_entries(struct bios_smap *smapbase, vm_paddr_t *physmap,
 	}
 }
 
+static void
+native_parse_memmap(caddr_t kmdp, vm_paddr_t *physmap, int *physmap_idx)
+{
+	struct bios_smap *smap;
+	u_int32_t size;
+
+	/*
+	 * Memory map from INT 15:E820.
+	 *
+	 * subr_module.c says:
+	 * "Consumer may safely assume that size value precedes data."
+	 * ie: an int32_t immediately precedes smap.
+	 */
+
+	smap = (struct bios_smap *)preload_search_info(kmdp,
+	    MODINFO_METADATA | MODINFOMD_SMAP);
+	if (smap == NULL)
+		panic("No BIOS smap info from loader!");
+	size = *((u_int32_t *)smap - 1);
+
+	bios_add_smap_entries(smap, size, physmap, physmap_idx);
+}
+
 /*
  * Populate the (physmap) array with base/bound pairs describing the
  * available physical memory in the system, then test this memory and
@@ -1451,19 +1469,13 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	vm_paddr_t pa, physmap[PHYSMAP_SIZE];
 	u_long physmem_start, physmem_tunable, memtest;
 	pt_entry_t *pte;
-	struct bios_smap *smapbase;
 	quad_t dcons_addr, dcons_size;
 
 	bzero(physmap, sizeof(physmap));
 	basemem = 0;
 	physmap_idx = 0;
 
-	smapbase = (struct bios_smap *)preload_search_info(kmdp,
-	    MODINFO_METADATA | MODINFOMD_SMAP);
-	if (smapbase == NULL)
-		panic("No BIOS smap info from loader!");
-
-	add_smap_entries(smapbase, physmap, &physmap_idx);
+	init_ops.parse_memmap(kmdp, physmap, &physmap_idx);
 
 	/*
 	 * Find the 'base memory' segment for SMP

sys/amd64/include/pc/bios.h

@@ -106,6 +106,8 @@ struct bios_oem {
 int	bios_oem_strings(struct bios_oem *oem, u_char *buffer, size_t maxlen);
 uint32_t bios_sigsearch(uint32_t start, u_char *sig, int siglen, int paralen,
 	    int sigofs);
+void bios_add_smap_entries(struct bios_smap *smapbase, u_int32_t smapsize,
+	    vm_paddr_t *physmap, int *physmap_idx);
 #endif
 
 #endif /* _MACHINE_PC_BIOS_H_ */

sys/x86/include/init.h

@@ -38,6 +38,7 @@ struct init_ops {
 	caddr_t	(*parse_preload_data)(u_int64_t);
 	void	(*early_clock_source_init)(void);
 	void	(*early_delay)(int);
+	void	(*parse_memmap)(caddr_t, vm_paddr_t *, int *);
 };
 
 extern struct init_ops init_ops;

sys/x86/xen/pv.c

@@ -49,6 +49,7 @@ __FBSDID("$FreeBSD$");
 #include <vm/vm_param.h>
 
 #include <x86/init.h>
+#include <machine/pc/bios.h>
 
 #include <xen/xen-os.h>
 #include <xen/hypervisor.h>
@@ -60,8 +61,11 @@ extern u_int64_t hammer_time(u_int64_t, u_int64_t);
 /* Xen initial function */
 uint64_t hammer_time_xen(start_info_t *, uint64_t);
 
+#define MAX_E820_ENTRIES	128
+
 /*--------------------------- Forward Declarations ---------------------------*/
 static caddr_t xen_pv_parse_preload_data(u_int64_t);
+static void xen_pv_parse_memmap(caddr_t, vm_paddr_t *, int *);
 
 /*-------------------------------- Global Data -------------------------------*/
 /* Xen init_ops implementation. */
@@ -69,8 +73,11 @@ struct init_ops xen_init_ops = {
 	.parse_preload_data =	xen_pv_parse_preload_data,
 	.early_clock_source_init =	xen_clock_init,
 	.early_delay =			xen_delay,
+	.parse_memmap =			xen_pv_parse_memmap,
 };
 
+static struct bios_smap xen_smap[MAX_E820_ENTRIES];
+
 /*-------------------------------- Xen PV init -------------------------------*/
 /*
  * First function called by the Xen PVH boot sequence.
@@ -189,3 +196,21 @@ xen_pv_parse_preload_data(u_int64_t modulep)
 
 	return (NULL);
 }
+
+static void
+xen_pv_parse_memmap(caddr_t kmdp, vm_paddr_t *physmap, int *physmap_idx)
+{
+	struct xen_memory_map memmap;
+	u_int32_t size;
+	int rc;
+
+	/* Fetch the E820 map from Xen */
+	memmap.nr_entries = MAX_E820_ENTRIES;
+	set_xen_guest_handle(memmap.buffer, xen_smap);
+	rc = HYPERVISOR_memory_op(XENMEM_memory_map, &memmap);
+	if (rc)
+		panic("unable to fetch Xen E820 memory map");
+	size = memmap.nr_entries * sizeof(xen_smap[0]);
+
+	bios_add_smap_entries(xen_smap, size, physmap, physmap_idx);
+}