From: Wei Liu <wei.liu2@citrix.com>

After the direct map removal, pages from the boot allocator are not
going to be mapped in the direct map. Although we have map_domain_page,
they are ephemeral and are less helpful for mappings that are more than a
page, so we want a mechanism to globally map a range of pages, which is
what vmap is for. Therefore, we bring vm_init into early boot stage.

To allow vmap to be initialised and used in early boot, we need to
modify vmap to receive pages from the boot allocator during early boot
stage.

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Woodhouse <dwmw2@amazon.com>
Signed-off-by: Hongyan Xia <hongyxia@amazon.com>
Signed-off-by: Julien Grall <jgrall@amazon.com>
Signed-off-by: Elias El Yandouzi <eliasely@amazon.com>

----

    Changes in v2:
        - The return of map_pages_to_xen() is now checked in a separate
          patch
        - Clarify the commit message
        - Group the new boolean with the others

diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
index 59dd9bb25a..7e28f62d09 100644
--- a/xen/arch/arm/setup.c
+++ b/xen/arch/arm/setup.c
@@ -748,6 +748,8 @@ void asmlinkage __init start_xen(unsigned long boot_phys_offset,
 
     setup_mm();
 
+    vm_init();
+
     /* Parse the ACPI tables for possible boot-time configuration */
     acpi_boot_table_init();
 
@@ -759,8 +761,6 @@ void asmlinkage __init start_xen(unsigned long boot_phys_offset,
      */
     system_state = SYS_STATE_boot;
 
-    vm_init();
-
     if ( acpi_disabled )
     {
         printk("Booting using Device Tree\n");
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index 897b7e9208..4d0c90b7a0 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -989,6 +989,7 @@ void asmlinkage __init noreturn __start_xen(unsigned long mbi_p)
     int i, j, e820_warn = 0, bytes = 0;
     unsigned long eb_start, eb_end;
     bool acpi_boot_table_init_done = false, relocated = false;
+    bool vm_init_done = false;
     int ret;
     struct ns16550_defaults ns16550 = {
         .data_bits = 8,
@@ -1531,12 +1532,23 @@ void asmlinkage __init noreturn __start_xen(unsigned long mbi_p)
             continue;
 
         if ( !acpi_boot_table_init_done &&
-             s >= (1ULL << 32) &&
-             !acpi_boot_table_init() )
+             s >= (1ULL << 32) )
         {
-            acpi_boot_table_init_done = true;
-            srat_parse_regions(s);
-            setup_max_pdx(raw_max_page);
+            /*
+             * We only initialise vmap and acpi after going through the bottom
+             * 4GiB, so that we have enough pages in the boot allocator.
+             */
+            if ( !vm_init_done )
+            {
+                vm_init();
+                vm_init_done = true;
+            }
+            if ( !acpi_boot_table_init() )
+            {
+                acpi_boot_table_init_done = true;
+                srat_parse_regions(s);
+                setup_max_pdx(raw_max_page);
+            }
         }
 
         if ( pfn_to_pdx((e - 1) >> PAGE_SHIFT) >= max_pdx )
@@ -1722,6 +1734,9 @@ void asmlinkage __init noreturn __start_xen(unsigned long mbi_p)
 
     init_frametable();
 
+    if ( !vm_init_done )
+        vm_init();
+
     if ( !acpi_boot_table_init_done )
         acpi_boot_table_init();
 
@@ -1761,12 +1776,6 @@ void asmlinkage __init noreturn __start_xen(unsigned long mbi_p)
         end_boot_allocator();
 
     system_state = SYS_STATE_boot;
-    /*
-     * No calls involving ACPI code should go between the setting of
-     * SYS_STATE_boot and vm_init() (or else acpi_os_{,un}map_memory()
-     * will break).
-     */
-    vm_init();
 
     bsp_stack = cpu_alloc_stack(0);
     if ( !bsp_stack )
diff --git a/xen/common/vmap.c b/xen/common/vmap.c
index 830f64c5ef..fc5c70da4d 100644
--- a/xen/common/vmap.c
+++ b/xen/common/vmap.c
@@ -34,10 +34,19 @@ void __init vm_init_type(enum vmap_region type, void *start, void *end)
 
     for ( i = 0, va = (unsigned long)vm_bitmap(type); i < nr; ++i, va += PAGE_SIZE )
     {
-        struct page_info *pg = alloc_domheap_page(NULL, 0);
+        mfn_t mfn;
         int rc;
 
-        rc = map_pages_to_xen(va, page_to_mfn(pg), 1, PAGE_HYPERVISOR);
+        if ( system_state == SYS_STATE_early_boot )
+            mfn = alloc_boot_pages(1, 1);
+        else
+        {
+            struct page_info *pg = alloc_domheap_page(NULL, 0);
+
+            BUG_ON(!pg);
+            mfn = page_to_mfn(pg);
+        }
+        rc = map_pages_to_xen(va, mfn, 1, PAGE_HYPERVISOR);
         BUG_ON(rc);
 
         clear_page((void *)va);
@@ -65,7 +74,7 @@ static void *vm_alloc(unsigned int nr, unsigned int align,
     spin_lock(&vm_lock);
     for ( ; ; )
     {
-        struct page_info *pg;
+        mfn_t mfn;
 
         ASSERT(vm_low[t] == vm_top[t] || !test_bit(vm_low[t], vm_bitmap(t)));
         for ( start = vm_low[t]; start < vm_top[t]; )
@@ -100,9 +109,16 @@ static void *vm_alloc(unsigned int nr, unsigned int align,
         if ( vm_top[t] >= vm_end[t] )
             return NULL;
 
-        pg = alloc_domheap_page(NULL, 0);
-        if ( !pg )
-            return NULL;
+        if ( system_state == SYS_STATE_early_boot )
+            mfn = alloc_boot_pages(1, 1);
+        else
+        {
+            struct page_info *pg = alloc_domheap_page(NULL, 0);
+
+            if ( !pg )
+                return NULL;
+            mfn = page_to_mfn(pg);
+        }
 
         spin_lock(&vm_lock);
 
@@ -110,7 +126,7 @@ static void *vm_alloc(unsigned int nr, unsigned int align,
         {
             unsigned long va = (unsigned long)vm_bitmap(t) + vm_top[t] / 8;
 
-            if ( !map_pages_to_xen(va, page_to_mfn(pg), 1, PAGE_HYPERVISOR) )
+            if ( !map_pages_to_xen(va, mfn, 1, PAGE_HYPERVISOR) )
             {
                 clear_page((void *)va);
                 vm_top[t] += PAGE_SIZE * 8;
@@ -120,7 +136,10 @@ static void *vm_alloc(unsigned int nr, unsigned int align,
             }
         }
 
-        free_domheap_page(pg);
+        if ( system_state == SYS_STATE_early_boot )
+            init_boot_pages(mfn_to_maddr(mfn), mfn_to_maddr(mfn) + PAGE_SIZE);
+        else
+            free_domheap_page(mfn_to_page(mfn));
 
         if ( start >= vm_top[t] )
         {
-- 
2.40.1