[PATCH v2] xen/arm/efi: merge neighboring banks

[Stefano Stabellini <stefano.stabellini@xxxxxxx>]

When booting from U-Boot bootefi, there can be a high number of
neighboring RAM banks. See for example:

(XEN) RAM: 0000000000000000 - 0000000000bfffff
(XEN) RAM: 0000000000c00000 - 0000000000c00fff
(XEN) RAM: 0000000000c01000 - 0000000000dfffff
(XEN) RAM: 0000000000e00000 - 000000000279dfff
(XEN) RAM: 000000000279e000 - 00000000029fffff
(XEN) RAM: 0000000002a00000 - 0000000008379fff
(XEN) RAM: 000000000837a000 - 00000000083fffff
(XEN) RAM: 0000000008400000 - 0000000008518fff
(XEN) RAM: 0000000008519000 - 00000000085fffff
(XEN) RAM: 0000000008600000 - 0000000008613fff
(XEN) RAM: 0000000008614000 - 00000000097fffff
(XEN) RAM: 0000000009800000 - 00000000098a7fff
(XEN) RAM: 00000000098a8000 - 0000000009dfffff
(XEN) RAM: 0000000009e00000 - 0000000009ea7fff
(XEN) RAM: 0000000009ea8000 - 000000001fffffff
(XEN) RAM: 0000000020000000 - 000000002007ffff
(XEN) RAM: 0000000020080000 - 0000000077b17fff
(XEN) RAM: 0000000077b19000 - 0000000077b2bfff
(XEN) RAM: 0000000077b2c000 - 0000000077c8dfff
(XEN) RAM: 0000000077c8e000 - 0000000077c91fff
(XEN) RAM: 0000000077ca7000 - 0000000077caafff
(XEN) RAM: 0000000077cac000 - 0000000077caefff
(XEN) RAM: 0000000077cd0000 - 0000000077cd2fff
(XEN) RAM: 0000000077cd4000 - 0000000077cd7fff
(XEN) RAM: 0000000077cd8000 - 000000007bd07fff
(XEN) RAM: 000000007bd09000 - 000000007fd5ffff
(XEN) RAM: 000000007fd70000 - 000000007fefffff
(XEN) RAM: 0000000800000000 - 000000087fffffff

Xen does not currently support boot modules that span multiple banks: at
least one of the regions get freed twice. The first time from
setup_mm->populate_boot_allocator, then again from
discard_initial_modules->fw_unreserved_regions. With a high number of
banks, it can be difficult to arrange the boot modules in a way that
avoids spanning across multiple banks.

This small patch merges neighboring regions, to make dealing with them
more efficient, and to make it easier to load boot modules.

Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxx>
---
Changes in v2:
- remove unneeded check for duplicates
- unsigned int instead of int
- add parenthesis
---
 xen/arch/arm/efi/efi-boot.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/xen/arch/arm/efi/efi-boot.h b/xen/arch/arm/efi/efi-boot.h
index a80a5a7ab3..8b8ef5dcfb 100644
--- a/xen/arch/arm/efi/efi-boot.h
+++ b/xen/arch/arm/efi/efi-boot.h
@@ -163,6 +163,16 @@ static bool __init meminfo_add_bank(struct membanks *mem,
     struct membank *bank;
     paddr_t start = desc->PhysicalStart;
     paddr_t size = desc->NumberOfPages * EFI_PAGE_SIZE;
+    unsigned int j;
+
+    for ( j = 0; j < mem->nr_banks; j++ )
+    {
+        if ( (mem->bank[j].start + mem->bank[j].size) == start )
+        {
+            mem->bank[j].size += size;
+            return true;
+        }
+    }
 
     if ( mem->nr_banks >= mem->max_banks )
         return false;
-- 
2.25.1