1 files changed, 13 insertions, 16 deletions

diff --git a/arch/x86/boot/memory.c b/arch/x86/boot/memory.c
index d989de810cac..cae3feb1035e 100644
--- a/arch/x86/boot/memory.c
+++ b/arch/x86/boot/memory.c
@@ -17,17 +17,12 @@
 
 #define SMAP    0x534d4150      /* ASCII "SMAP" */
 
-struct e820_ext_entry {
-        struct e820entry std;
-        u32 ext_flags;
-} __attribute__((packed));
-
 static int detect_memory_e820(void)
 {
         int count = 0;
         struct biosregs ireg, oreg;
         struct e820entry *desc = boot_params.e820_map;
-        static struct e820_ext_entry buf; /* static so it is zeroed */
+        static struct e820entry buf; /* static so it is zeroed */
 
         initregs(&ireg);
         ireg.ax  = 0xe820;
@@ -36,10 +31,18 @@ static int detect_memory_e820(void)
         ireg.di  = (size_t)&buf;
 
         /*
-         * Set this here so that if the BIOS doesn't change this field
-         * but still doesn't change %ecx, we're still okay...
+         * Note: at least one BIOS is known which assumes that the
+         * buffer pointed to by one e820 call is the same one as
+         * the previous call, and only changes modified fields.  Therefore,
+         * we use a temporary buffer and copy the results entry by entry.
+         *
+         * This routine deliberately does not try to account for
+         * ACPI 3+ extended attributes.  This is because there are
+         * BIOSes in the field which report zero for the valid bit for
+         * all ranges, and we don't currently make any use of the
+         * other attribute bits.  Revisit this if we see the extended
+         * attribute bits deployed in a meaningful way in the future.
          */
-        buf.ext_flags = 1;
 
         do {
                 intcall(0x15, &ireg, &oreg);
@@ -61,13 +64,7 @@ static int detect_memory_e820(void)
                         break;
                 }
 
-                /* ACPI 3.0 added the extended flags support.  If bit 0
-                   in the extended flags is zero, we're supposed to simply
-                   ignore the entry -- a backwards incompatible change! */
-                if (oreg.cx > 20 && !(buf.ext_flags & 1))
-                        continue;
-
-                *desc++ = buf.std;
+                *desc++ = buf;
                 count++;
         } while (ireg.ebx && count < ARRAY_SIZE(boot_params.e820_map));