[Xen-devel] [PATCH v2] efi/boot: Don't free ebmalloc area at all

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

Freeing part of the BSS back for general use proves to be problematic.  It is
not accounted for in xen_in_range(), causing errors when constructing the
IOMMU tables, resulting in a failure to boot.

Other smaller issues are that tboot treats the entire BSS as hypervisor data,
creating and checking a MAC of it on S3, and that, by being 1MB in size,
freeing it guarentees to shatter the hypervisor superpage mappings.

This is a stopgap fix to unblock master, while alternatives are discussed.

Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
---
CC: Jan Beulich <JBeulich@xxxxxxxx>
---
 xen/common/efi/boot.c | 16 ----------------
 1 file changed, 16 deletions(-)

diff --git a/xen/common/efi/boot.c b/xen/common/efi/boot.c
index b6cbdad..2341889 100644
--- a/xen/common/efi/boot.c
+++ b/xen/common/efi/boot.c
@@ -120,7 +120,6 @@ static CHAR16 __initdata newline[] = L"\r\n";
  *     have to be disabled in xen/arch/arm/arm64/head.S; though BSS
  *     should be initialized somehow before use of variables living there,
  *   - use ebmalloc() in ARM/common EFI boot code,
- *   - call free_ebmalloc_unused_mem() somewhere in init code.
  */
 #define EBMALLOC_SIZE  MB(0)
 #else
@@ -144,19 +143,6 @@ static void __init __maybe_unused *ebmalloc(size_t size)
     return ptr;
 }
 
-static void __init __maybe_unused free_ebmalloc_unused_mem(void)
-{
-    unsigned long start, end;
-
-    start = (unsigned long)ebmalloc_mem + PAGE_ALIGN(ebmalloc_allocated);
-    end = (unsigned long)ebmalloc_mem + sizeof(ebmalloc_mem);
-
-    destroy_xen_mappings(start, end);
-    init_xenheap_pages(__pa(start), __pa(end));
-
-    printk(XENLOG_INFO "Freed %lukB unused BSS memory\n", (end - start) >> 10);
-}
-
 /*
  * Include architecture specific implementation here, which references the
  * static globals defined above.
@@ -1310,8 +1296,6 @@ void __init efi_init_memory(void)
     } *extra, *extra_head = NULL;
 #endif
 
-    free_ebmalloc_unused_mem();
-
     if ( !efi_enabled(EFI_BOOT) )
         return;
 
-- 
2.1.4


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel