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authorLinus Torvalds <torvalds@linux-foundation.org>2013-02-27 16:16:39 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2013-02-27 16:16:39 -0800
commit18a44a7ff1075ce5157ac07cde573aca6b5e9973 (patch)
tree8b857b12887da983b75bfd0d693df23edb810ba5 /arch/x86/kernel
parent309667e53fcfd8e0b423280b6ea5a648fd92166c (diff)
parent7c10093692ed2e6f318387d96b829320aa0ca64c (diff)
downloadvexpress-lsk-18a44a7ff1075ce5157ac07cde573aca6b5e9973.tar.gz
Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull more x86 fixes from Peter Anvin: "Additional x86 fixes. Three of these patches are pure documentation, two are pretty trivial; the remaining one fixes boot problems on some non-BIOS machines." * 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: x86: Make sure we can boot in the case the BDA contains pure garbage x86, efi: Mark disable_runtime as __initdata x86, doc: Fix incorrect comment about 64-bit code segment descriptors doc, kernel-parameters: Document 'console=hvc<n>' doc, xen: Mention 'earlyprintk=xen' in the documentation. ACPI: Overriding ACPI tables via initrd only works with an initrd and on X86
Diffstat (limited to 'arch/x86/kernel')
-rw-r--r--arch/x86/kernel/head.c53
-rw-r--r--arch/x86/kernel/head_64.S4
2 files changed, 36 insertions, 21 deletions
diff --git a/arch/x86/kernel/head.c b/arch/x86/kernel/head.c
index 48d9d4ea102..992f442ca15 100644
--- a/arch/x86/kernel/head.c
+++ b/arch/x86/kernel/head.c
@@ -5,8 +5,6 @@
#include <asm/setup.h>
#include <asm/bios_ebda.h>
-#define BIOS_LOWMEM_KILOBYTES 0x413
-
/*
* The BIOS places the EBDA/XBDA at the top of conventional
* memory, and usually decreases the reported amount of
@@ -16,17 +14,30 @@
* chipset: reserve a page before VGA to prevent PCI prefetch
* into it (errata #56). Usually the page is reserved anyways,
* unless you have no PS/2 mouse plugged in.
+ *
+ * This functions is deliberately very conservative. Losing
+ * memory in the bottom megabyte is rarely a problem, as long
+ * as we have enough memory to install the trampoline. Using
+ * memory that is in use by the BIOS or by some DMA device
+ * the BIOS didn't shut down *is* a big problem.
*/
+
+#define BIOS_LOWMEM_KILOBYTES 0x413
+#define LOWMEM_CAP 0x9f000U /* Absolute maximum */
+#define INSANE_CUTOFF 0x20000U /* Less than this = insane */
+
void __init reserve_ebda_region(void)
{
unsigned int lowmem, ebda_addr;
- /* To determine the position of the EBDA and the */
- /* end of conventional memory, we need to look at */
- /* the BIOS data area. In a paravirtual environment */
- /* that area is absent. We'll just have to assume */
- /* that the paravirt case can handle memory setup */
- /* correctly, without our help. */
+ /*
+ * To determine the position of the EBDA and the
+ * end of conventional memory, we need to look at
+ * the BIOS data area. In a paravirtual environment
+ * that area is absent. We'll just have to assume
+ * that the paravirt case can handle memory setup
+ * correctly, without our help.
+ */
if (paravirt_enabled())
return;
@@ -37,19 +48,23 @@ void __init reserve_ebda_region(void)
/* start of EBDA area */
ebda_addr = get_bios_ebda();
- /* Fixup: bios puts an EBDA in the top 64K segment */
- /* of conventional memory, but does not adjust lowmem. */
- if ((lowmem - ebda_addr) <= 0x10000)
- lowmem = ebda_addr;
+ /*
+ * Note: some old Dells seem to need 4k EBDA without
+ * reporting so, so just consider the memory above 0x9f000
+ * to be off limits (bugzilla 2990).
+ */
+
+ /* If the EBDA address is below 128K, assume it is bogus */
+ if (ebda_addr < INSANE_CUTOFF)
+ ebda_addr = LOWMEM_CAP;
- /* Fixup: bios does not report an EBDA at all. */
- /* Some old Dells seem to need 4k anyhow (bugzilla 2990) */
- if ((ebda_addr == 0) && (lowmem >= 0x9f000))
- lowmem = 0x9f000;
+ /* If lowmem is less than 128K, assume it is bogus */
+ if (lowmem < INSANE_CUTOFF)
+ lowmem = LOWMEM_CAP;
- /* Paranoia: should never happen, but... */
- if ((lowmem == 0) || (lowmem >= 0x100000))
- lowmem = 0x9f000;
+ /* Use the lower of the lowmem and EBDA markers as the cutoff */
+ lowmem = min(lowmem, ebda_addr);
+ lowmem = min(lowmem, LOWMEM_CAP); /* Absolute cap */
/* reserve all memory between lowmem and the 1MB mark */
memblock_reserve(lowmem, 0x100000 - lowmem);
diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
index b7de3b25adb..6859e962644 100644
--- a/arch/x86/kernel/head_64.S
+++ b/arch/x86/kernel/head_64.S
@@ -48,7 +48,7 @@ L3_START_KERNEL = pud_index(__START_KERNEL_map)
.globl startup_64
startup_64:
/*
- * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
+ * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
* and someone has loaded an identity mapped page table
* for us. These identity mapped page tables map all of the
* kernel pages and possibly all of memory.
@@ -159,7 +159,7 @@ startup_64:
jmp 1f
ENTRY(secondary_startup_64)
/*
- * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 1,
+ * At this point the CPU runs in 64bit mode CS.L = 1 CS.D = 0,
* and someone has loaded a mapped page table.
*
* %rsi holds a physical pointer to real_mode_data.