arm64: Move cpu0 dpcpu and msgbuf to the DMAP

When these are allocated we already have the DMAP region mapped. Search
for the largest region and use this to hold these.

Pr:		269726
Reviewed by:	markj
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D42734

sys/arm64/arm64/pmap.c

@@ -1332,6 +1332,7 @@ pmap_bootstrap(void)
 {
 	vm_offset_t dpcpu, msgbufpv;
 	vm_paddr_t start_pa, pa;
+	size_t largest_phys_size;
 
 	/* Set this early so we can use the pagetable walking functions */
 	kernel_pmap_store.pm_l0 = pagetable_l0_ttbr1;
@@ -1346,12 +1347,41 @@ pmap_bootstrap(void)
 	kernel_pmap->pm_ttbr = kernel_pmap->pm_l0_paddr;
 	kernel_pmap->pm_asid_set = &asids;
 
+	/* Reserve some VA space for early BIOS/ACPI mapping */
+	preinit_map_va = roundup2(bs_state.freemempos, L2_SIZE);
+
+	virtual_avail = preinit_map_va + PMAP_PREINIT_MAPPING_SIZE;
+	virtual_avail = roundup2(virtual_avail, L1_SIZE);
+	virtual_end = VM_MAX_KERNEL_ADDRESS - PMAP_MAPDEV_EARLY_SIZE;
+	kernel_vm_end = virtual_avail;
+
 	/*
 	 * We only use PXN when we know nothing will be executed from it, e.g.
 	 * the DMAP region.
 	 */
 	bs_state.table_attrs &= ~TATTR_PXN_TABLE;
 
+	/*
+	 * Find the physical memory we could use. This needs to be after we
+	 * exclude any memory that is mapped into the DMAP region but should
+	 * not be used by the kernel, e.g. some UEFI memory types.
+	 */
+	physmap_idx = physmem_avail(physmap, nitems(physmap));
+
+	/*
+	 * Find space for early allocations. We search for the largest
+	 * region. This is because the user may choose a large msgbuf.
+	 * This could be smarter, e.g. to allow multiple regions to be
+	 * used & switch to the next when one is full.
+	 */
+	largest_phys_size = 0;
+	for (int i = 0; i < physmap_idx; i += 2) {
+		if ((physmap[i + 1] - physmap[i]) > largest_phys_size) {
+			largest_phys_size = physmap[i + 1] - physmap[i];
+			bs_state.freemempos = PHYS_TO_DMAP(physmap[i]);
+		}
+	}
+
 	start_pa = pmap_early_vtophys(bs_state.freemempos);
 
 	/*
@@ -1378,19 +1408,9 @@ pmap_bootstrap(void)
 	alloc_pages(msgbufpv, round_page(msgbufsize) / PAGE_SIZE);
 	msgbufp = (void *)msgbufpv;
 
-	/* Reserve some VA space for early BIOS/ACPI mapping */
-	preinit_map_va = roundup2(bs_state.freemempos, L2_SIZE);
-
-	virtual_avail = preinit_map_va + PMAP_PREINIT_MAPPING_SIZE;
-	virtual_avail = roundup2(virtual_avail, L1_SIZE);
-	virtual_end = VM_MAX_KERNEL_ADDRESS - (PMAP_MAPDEV_EARLY_SIZE);
-	kernel_vm_end = virtual_avail;
-
 	pa = pmap_early_vtophys(bs_state.freemempos);
 
 	physmem_exclude_region(start_pa, pa - start_pa, EXFLAG_NOALLOC);
-
-	cpu_tlb_flushID();
 }
 
 #if defined(KASAN) || defined(KMSAN)