From 217732b47df4884c66c89cb08c351e01ec4c1667 Mon Sep 17 00:00:00 2001
From: royger <royger@FreeBSD.org>
Date: Mon, 26 Jan 2015 08:42:47 +0000
Subject: [PATCH] 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
---
 sys/amd64/amd64/machdep.c | 38 +++++++++++++++++++++++++-------------
 1 file changed, 25 insertions(+), 13 deletions(-)

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index 07378fddce3..839da018cc3 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1355,8 +1355,10 @@ 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]) {
@@ -1394,7 +1396,7 @@ 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];
 	}
@@ -1580,23 +1582,27 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	int page_counter;
 
 	bzero(physmap, sizeof(physmap));
-	basemem = 0;
 	physmap_idx = 0;
 
 	init_ops.parse_memmap(kmdp, physmap, &physmap_idx);
+	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;
+	}
 
 	/*
 	 * Make hole for "AP -> long mode" bootstrap code.  The
@@ -1604,8 +1610,12 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	 * is configured to support APs and APs for the system start
 	 * in 32bit mode (e.g. SMP bare metal).
 	 */
-	if (init_ops.mp_bootaddress)
+	if (init_ops.mp_bootaddress) {
+		if (physmap[1] >= 0x100000000)
+			panic(
+	"Basemem segment is not suitable for AP bootstrap code!");
 		physmap[1] = init_ops.mp_bootaddress(physmap[1] / 1024);
+	}
 
 	/*
 	 * Maxmem isn't the "maximum memory", it's one larger than the
@@ -1657,12 +1667,14 @@ 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];
-- 
2.45.0