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.

2 files changed, 26 insertions, 0 deletions

diff --git a/sys/x86/include/init.h b/sys/x86/include/init.h
index c72889f..562e582 100644
--- a/sys/x86/include/init.h
+++ b/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;
diff --git a/sys/x86/xen/pv.c b/sys/x86/xen/pv.c
index 4bc7e86..f7d5e47 100644
--- a/sys/x86/xen/pv.c
+++ b/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);
+}