4 files changed, 44 insertions, 21 deletions

diff --git a/sys/amd64/amd64/machdep.c b/sys/amd64/amd64/machdep.c
index a24546df23178..22cdb3fe6c22e 100644
--- a/sys/amd64/amd64/machdep.c
+++ b/sys/amd64/amd64/machdep.c
@@ -1246,14 +1246,10 @@ getmemsize(caddr_t kmdp, u_int64_t first)
 	 * Make hole for "AP -> long mode" bootstrap code.  The
 	 * mp_bootaddress vector is only available when the kernel
 	 * is configured to support APs and APs for the system start
-	 * in 32bit mode (e.g. SMP bare metal).
+	 * in real mode mode (e.g. SMP bare metal).
 	 */
-	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);
-	}
+	if (init_ops.mp_bootaddress)
+		init_ops.mp_bootaddress(physmap, &physmap_idx);
 
 	/*
 	 * Maxmem isn't the "maximum memory", it's one larger than the
diff --git a/sys/amd64/amd64/mp_machdep.c b/sys/amd64/amd64/mp_machdep.c
index 34012d2b4f968..7ef2c241e042a 100644
--- a/sys/amd64/amd64/mp_machdep.c
+++ b/sys/amd64/amd64/mp_machdep.c
@@ -96,24 +96,45 @@ char *nmi_stack;
 
 static int	start_ap(int apic_id);
 
-static u_int	bootMP_size;
-static u_int	boot_address;
-
 /*
  * Calculate usable address in base memory for AP trampoline code.
  */
-u_int
-mp_bootaddress(u_int basemem)
+void
+mp_bootaddress(vm_paddr_t *physmap, unsigned int *physmap_idx)
 {
+	unsigned int i;
+	bool allocated;
+
+	alloc_ap_trampoline(physmap, physmap_idx);
 
-	bootMP_size = mptramp_end - mptramp_start;
-	boot_address = trunc_page(basemem * 1024); /* round down to 4k boundary */
-	if (((basemem * 1024) - boot_address) < bootMP_size)
-		boot_address -= PAGE_SIZE;	/* not enough, lower by 4k */
-	/* 3 levels of page table pages */
-	mptramp_pagetables = boot_address - (PAGE_SIZE * 3);
+	allocated = false;
+	for (i = *physmap_idx; i <= *physmap_idx; i -= 2) {
+		/*
+		 * Find a memory region big enough below the 4GB boundary to
+		 * store the initial page tables. Note that it needs to be
+		 * aligned to a page boundary.
+		 */
+		if (physmap[i] >= GiB(4) ||
+		    (physmap[i + 1] - round_page(physmap[i])) < (PAGE_SIZE * 3))
+			continue;
 
-	return mptramp_pagetables;
+		allocated = true;
+		mptramp_pagetables = round_page(physmap[i]);
+		physmap[i] = round_page(physmap[i]) + (PAGE_SIZE * 3);
+		if (physmap[i] == physmap[i + 1] && *physmap_idx != 0) {
+			memmove(&physmap[i], &physmap[i + 2],
+			    sizeof(*physmap) * (*physmap_idx - i + 2));
+			*physmap_idx -= 2;
+		}
+	}
+
+	if (!allocated) {
+		mptramp_pagetables = trunc_page(boot_address) - (PAGE_SIZE * 3);
+		if (bootverbose)
+			printf(
+"Cannot find enough space for the initial AP page tables, placing them at %#x",
+			    mptramp_pagetables);
+	}
 }
 
 /*
diff --git a/sys/amd64/amd64/mpboot.S b/sys/amd64/amd64/mpboot.S
index 8af5a7898c9a2..5545fe9290d14 100644
--- a/sys/amd64/amd64/mpboot.S
+++ b/sys/amd64/amd64/mpboot.S
@@ -216,8 +216,14 @@ lgdt_desc:
 	.word	gdtend-gdt		/* Length */
 	.long	gdt-mptramp_start	/* Offset plus %ds << 4 */
 
-	.globl	mptramp_end
 mptramp_end:
+	/*
+	 * The size of the trampoline code that needs to be relocated
+	 * below the 1MiB boundary.
+	 */
+	.globl	bootMP_size
+bootMP_size:
+	.long	mptramp_end - mptramp_start
 
 	/*
 	 * From here on down is executed in the kernel .text section.
diff --git a/sys/amd64/include/smp.h b/sys/amd64/include/smp.h
index 64135bc36f580..2ecfe62cf9fbf 100644
--- a/sys/amd64/include/smp.h
+++ b/sys/amd64/include/smp.h
@@ -23,7 +23,6 @@
 
 /* global symbols in mpboot.S */
 extern char			mptramp_start[];
-extern char			mptramp_end[];
 extern u_int32_t		mptramp_pagetables;
 
 /* IPI handlers */
@@ -59,6 +58,7 @@ void	invlpg_pcid_handler(void);
 void	invlrng_invpcid_handler(void);
 void	invlrng_pcid_handler(void);
 int	native_start_all_aps(void);
+void	mp_bootaddress(vm_paddr_t *, unsigned int *);
 
 #endif /* !LOCORE */
 #endif /* SMP */