MFC r277735 (by royger):

amd64: allow base memory segment to start at address different than 0

Current code requires that the first physical memory segment starts at 0,
but this is not really needed. We only need to make sure the bootstrap code
and page tables for APs are allocated below 4GB.

This patch removes this requirement and allows booting a Dell R710 from
UEFI, where the first physical memory segment starts at 0x10000.

Sponsored by: Citrix Systems R&D
Reviewed by: jhb
Differential Revision: https://reviews.freebsd.org/D1417

1 files changed, 23 insertions, 12 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index d20e3121..fb1c0d9 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1344,8 +1344,10 @@ add_physmap_entry(uint64_t base, uint64_t length, vm_paddr_t *physmap,
 	/*
 	 * Find insertion point while checking for overlap.  Start off by
 	 * assuming the new entry will be added to the end.
+	 *
+	 * NB: physmap_idx points to the next free slot.
 	 */
-	insert_idx = physmap_idx + 2;
+	insert_idx = physmap_idx;
 	for (i = 0; i <= physmap_idx; i += 2) {
 		if (base < physmap[i + 1]) {
 			if (base + length <= physmap[i]) {
@@ -1383,7 +1385,7 @@ add_physmap_entry(uint64_t base, uint64_t length, vm_paddr_t *physmap,
 	 * Move the last 'N' entries down to make room for the new
 	 * entry if needed.
 	 */
-	for (i = physmap_idx; i > insert_idx; i -= 2) {
+	for (i = (physmap_idx - 2); i > insert_idx; i -= 2) {
 		physmap[i] = physmap[i - 2];
 		physmap[i + 1] = physmap[i - 1];
 	}
@@ -1548,7 +1550,6 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	int page_counter;
 
 	bzero(physmap, sizeof(physmap));
-	basemem = 0;
 	physmap_idx = 0;
 
 	efihdr = (struct efi_map_header *)preload_search_info(kmdp,
@@ -1566,21 +1567,29 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 		panic("No BIOS smap or EFI map info from loader!");
 	}
 
+	physmap_idx -= 2;
+
 	/*
 	 * Find the 'base memory' segment for SMP
 	 */
 	basemem = 0;
 	for (i = 0; i <= physmap_idx; i += 2) {
-		if (physmap[i] == 0x00000000) {
+		if (physmap[i] <= 0xA0000) {
 			basemem = physmap[i + 1] / 1024;
 			break;
 		}
 	}
-	if (basemem == 0)
-		panic("BIOS smap did not include a basemem segment!");
+	if (basemem == 0 || basemem > 640) {
+		if (bootverbose)
+			printf(
+		"Memory map doesn't contain a basemem segment, faking it");
+		basemem = 640;
+	}
 
 #ifdef SMP
 	/* make hole for AP bootstrap code */
+	if (physmap[1] >= 0x100000000)
+		panic("Basemem segment is not suitable for AP bootstrap code!");
 	physmap[1] = mp_bootaddress(physmap[1] / 1024);
 #endif
 
@@ -1634,12 +1643,14 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	 */
 	physmem_start = (vm_guest > VM_GUEST_NO ? 1 : 16) << PAGE_SHIFT;
 	TUNABLE_ULONG_FETCH("hw.physmem.start", &physmem_start);
-	if (physmem_start < PAGE_SIZE)
-		physmap[0] = PAGE_SIZE;
-	else if (physmem_start >= physmap[1])
-		physmap[0] = round_page(physmap[1] - PAGE_SIZE);
-	else
-		physmap[0] = round_page(physmem_start);
+	if (physmap[0] < physmem_start) {
+		if (physmem_start < PAGE_SIZE)
+			physmap[0] = PAGE_SIZE;
+		else if (physmem_start >= physmap[1])
+			physmap[0] = round_page(physmap[1] - PAGE_SIZE);
+		else
+			physmap[0] = round_page(physmem_start);
+	}
 	pa_indx = 0;
 	da_indx = 1;
 	phys_avail[pa_indx++] = physmap[0];