efi_loader: Reserve unaccessible memory

On some systems, not all RAM may be usable within U-Boot. Maybe the
memory maps are incomplete, maybe it's used as workaround for broken
DMA. But whatever the reason may be, a platform can say that it does
not wish to have its RAM accessed above a certain address by defining
board_get_usable_ram_top().

In the efi_loader world, we ignored that hint, mostly because very few
boards actually have real restrictions around this.

So let's honor the board's wish to not access high addresses during
boot time. The best way to do so is by indicating the respective pages
as "allocated by firmware". That way, Operating Systems will still
use the pages after boot, but before boot no allocation will use them.

Reported-by: Baruch Siach <baruch@tkos.co.il>
Signed-off-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Stephen Warren <swarren@nvidia.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
Tested-by: Baruch Siach <baruch@tkos.co.il>

diff --git a/include/common.h b/include/common.h
index 8b561370326f63f64201f668d707b87b446e5099..a8e879e1b9a5a011c8df9a4690367c9228cb238e 100644 (file)
--- a/include/common.h
+++ b/include/common.h
@@ -105,6 +105,17 @@ int mdm_init(void);
  */
 void board_show_dram(phys_size_t size);
 
+/**
+ * Get the uppermost pointer that is valid to access
+ *
+ * Some systems may not map all of their address space. This function allows
+ * boards to indicate what their highest support pointer value is for DRAM
+ * access.
+ *
+ * @param total_size   Size of U-Boot (unused?)
+ */
+ulong board_get_usable_ram_top(ulong total_size);
+
 /**
  * arch_fixup_fdt() - Write arch-specific information to fdt
  *

diff --git a/lib/efi_loader/efi_memory.c b/lib/efi_loader/efi_memory.c
index f225a9028c5d22296f7be6e0d8151e5756ca71e5..73bfbb65c4d3a790406954d826b1e1805d7202b4 100644 (file)
--- a/lib/efi_loader/efi_memory.c
+++ b/lib/efi_loader/efi_memory.c
@@ -551,8 +551,13 @@ efi_status_t efi_get_memory_map(efi_uintn_t *memory_map_size,
 
 __weak void efi_add_known_memory(void)
 {
+       u64 ram_top = board_get_usable_ram_top(0) & ~EFI_PAGE_MASK;
        int i;
 
+       /* Fix for 32bit targets with ram_top at 4G */
+       if (!ram_top)
+               ram_top = 0x100000000ULL;
+
        /* Add RAM */
        for (i = 0; i < CONFIG_NR_DRAM_BANKS; i++) {
                u64 ram_end, ram_start, pages;
@@ -564,11 +569,32 @@ __weak void efi_add_known_memory(void)
                ram_end &= ~EFI_PAGE_MASK;
                ram_start = (ram_start + EFI_PAGE_MASK) & ~EFI_PAGE_MASK;
 
-               if (ram_end > ram_start) {
-                       pages = (ram_end - ram_start) >> EFI_PAGE_SHIFT;
+               if (ram_end <= ram_start) {
+                       /* Invalid mapping, keep going. */
+                       continue;
+               }
+
+               pages = (ram_end - ram_start) >> EFI_PAGE_SHIFT;
 
+               efi_add_memory_map(ram_start, pages,
+                                  EFI_CONVENTIONAL_MEMORY, false);
+
+               /*
+                * Boards may indicate to the U-Boot memory core that they
+                * can not support memory above ram_top. Let's honor this
+                * in the efi_loader subsystem too by declaring any memory
+                * above ram_top as "already occupied by firmware".
+                */
+               if (ram_top < ram_start) {
+                       /* ram_top is before this region, reserve all */
                        efi_add_memory_map(ram_start, pages,
-                                          EFI_CONVENTIONAL_MEMORY, false);
+                                          EFI_BOOT_SERVICES_DATA, true);
+               } else if ((ram_top >= ram_start) && (ram_top < ram_end)) {
+                       /* ram_top is inside this region, reserve parts */
+                       pages = (ram_end - ram_top) >> EFI_PAGE_SHIFT;
+
+                       efi_add_memory_map(ram_top, pages,
+                                          EFI_BOOT_SERVICES_DATA, true);
                }
        }
 }