[Xen-devel] [PATCH v3 3/6] xen/arm: keep track of reserved-memory regions

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

As we parse the device tree in Xen, keep track of the reserved-memory
regions as they need special treatment (follow-up patches will make use
of the stored information.)

Reuse process_memory_node to add reserved-memory regions to the
bootinfo.reserved_mem array.

Refuse to continue once we reach the max number of reserved memory
regions to avoid accidentally mapping any portions of them into a VM.

Signed-off-by: Stefano Stabellini <stefanos@xxxxxxxxxx>

---
It is cleaner to avoid sharing the whole function process_memory_node
between the normal memory case and the reserved-memory case. I'll do it
in the next version once I understand the best way do to it.

---
Changes in v3:
- match only /reserved-memory
- put the warning back in place for reg not present on a normal memory
  region
- refuse to continue once we reach the max number of reserved memory
  regions

Changes in v2:
- call process_memory_node from process_reserved_memory_node to avoid
  duplication
---
 xen/arch/arm/bootfdt.c      | 38 +++++++++++++++++++++++++++++++------
 xen/include/asm-arm/setup.h |  1 +
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/xen/arch/arm/bootfdt.c b/xen/arch/arm/bootfdt.c
index 611724433b..b24ab10cb9 100644
--- a/xen/arch/arm/bootfdt.c
+++ b/xen/arch/arm/bootfdt.c
@@ -135,6 +135,8 @@ static int __init process_memory_node(const void *fdt, int 
node,
     const __be32 *cell;
     paddr_t start, size;
     u32 reg_cells = address_cells + size_cells;
+    struct meminfo *mem;
+    bool reserved = (bool)data;
 
     if ( address_cells < 1 || size_cells < 1 )
     {
@@ -143,29 +145,49 @@ static int __init process_memory_node(const void *fdt, 
int node,
         return 0;
     }
 
+    if ( reserved )
+        mem = &bootinfo.reserved_mem;
+    else
+        mem = &bootinfo.mem;
+
     prop = fdt_get_property(fdt, node, "reg", NULL);
     if ( !prop )
     {
-        printk("fdt: node `%s': missing `reg' property\n", name);
+        if ( !reserved )
+            printk("fdt: node `%s': missing `reg' property\n", name);
         return 0;
     }
 
     cell = (const __be32 *)prop->data;
     banks = fdt32_to_cpu(prop->len) / (reg_cells * sizeof (u32));
 
-    for ( i = 0; i < banks && bootinfo.mem.nr_banks < NR_MEM_BANKS; i++ )
+    for ( i = 0; i < banks && mem->nr_banks < NR_MEM_BANKS; i++ )
     {
         device_tree_get_reg(&cell, address_cells, size_cells, &start, &size);
         if ( !size )
             continue;
-        bootinfo.mem.bank[bootinfo.mem.nr_banks].start = start;
-        bootinfo.mem.bank[bootinfo.mem.nr_banks].size = size;
-        bootinfo.mem.nr_banks++;
+        mem->bank[mem->nr_banks].start = start;
+        mem->bank[mem->nr_banks].size = size;
+        mem->nr_banks++;
     }
+    /*
+     * We reached the max number of supported reserved-memory regions.
+     * Stop and refuse to continue. We don't want to risk Xen allocating
+     * those regions as normal memory to a VM.
+     */
+    BUG_ON(reserved && mem->nr_banks == NR_MEM_BANKS);
 
     return 0;
 }
 
+static int __init process_reserved_memory_node(const void *fdt, int node,
+                                               const char *name, int depth,
+                                               u32 address_cells, u32 
size_cells)
+{
+    device_tree_for_each_node(fdt, node, depth, process_memory_node, 
(void*)true);
+    return 0;
+}
+
 static void __init process_multiboot_node(const void *fdt, int node,
                                           const char *name,
                                           u32 address_cells, u32 size_cells)
@@ -299,7 +321,11 @@ static int __init early_scan_node(const void *fdt,
 
     if ( device_tree_node_matches(fdt, node, "memory") )
         rc = process_memory_node(fdt, node, name, depth,
-                                 address_cells, size_cells, NULL);
+                                 address_cells, size_cells, (void*)false);
+    else if ( depth == 1 && !strcmp(name, "reserved-memory") &&
+              strlen(name) == strlen("reserved-memory") )
+        rc = process_reserved_memory_node(fdt, node, name, depth,
+                                          address_cells, size_cells);
     else if ( depth <= 3 && (device_tree_node_compatible(fdt, node, 
"xen,multiboot-module" ) ||
               device_tree_node_compatible(fdt, node, "multiboot,module" )))
         process_multiboot_node(fdt, node, name, address_cells, size_cells);
diff --git a/xen/include/asm-arm/setup.h b/xen/include/asm-arm/setup.h
index 8bf3d5910a..efcba545c2 100644
--- a/xen/include/asm-arm/setup.h
+++ b/xen/include/asm-arm/setup.h
@@ -66,6 +66,7 @@ struct bootcmdlines {
 
 struct bootinfo {
     struct meminfo mem;
+    struct meminfo reserved_mem;
     struct bootmodules modules;
     struct bootcmdlines cmdlines;
 #ifdef CONFIG_ACPI
-- 
2.17.1


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