2 files changed, 58 insertions, 95 deletions

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index a1bd569f6c5a..b8676498d8df 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1341,25 +1341,34 @@ config X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK
           Set whether the default state of memory_corruption_check is
           on or off.
 
-config X86_RESERVE_LOW_64K
-        bool "Reserve low 64K of RAM on AMI/Phoenix BIOSen"
-        default y
-        ---help---
-          Reserve the first 64K of physical RAM on BIOSes that are known
-          to potentially corrupt that memory range. A numbers of BIOSes are
-          known to utilize this area during suspend/resume, so it must not
-          be used by the kernel.
-
-          Set this to N if you are absolutely sure that you trust the BIOS
-          to get all its memory reservations and usages right.
-
-          If you have doubts about the BIOS (e.g. suspend/resume does not
-          work or there's kernel crashes after certain hardware hotplug
-          events) and it's not AMI or Phoenix, then you might want to enable
-          X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check typical
-          corruption patterns.
-
-          Say Y if unsure.
+config X86_RESERVE_LOW
+        int "Amount of low memory, in kilobytes, to reserve for the BIOS"
+        default 64
+        range 4 640
+        ---help---
+          Specify the amount of low memory to reserve for the BIOS.
+
+          The first page contains BIOS data structures that the kernel
+          must not use, so that page must always be reserved.
+
+          By default we reserve the first 64K of physical RAM, as a
+          number of BIOSes are known to corrupt that memory range
+          during events such as suspend/resume or monitor cable
+          insertion, so it must not be used by the kernel.
+
+          You can set this to 4 if you are absolutely sure that you
+          trust the BIOS to get all its memory reservations and usages
+          right.  If you know your BIOS have problems beyond the
+          default 64K area, you can set this to 640 to avoid using the
+          entire low memory range.
+
+          If you have doubts about the BIOS (e.g. suspend/resume does
+          not work or there's kernel crashes after certain hardware
+          hotplug events) then you might want to enable
+          X86_CHECK_BIOS_CORRUPTION=y to allow the kernel to check
+          typical corruption patterns.
+
+          Leave this to the default value of 64 if you are unsure.
 
 config MATH_EMULATION
         bool
diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c
index df770ad99b3e..6154701a5fd3 100644
--- a/arch/x86/kernel/setup.c
+++ b/arch/x86/kernel/setup.c
@@ -619,79 +619,7 @@ static __init void reserve_ibft_region(void)
                 reserve_early_overlap_ok(addr, addr + size, "ibft");
 }
 
-#ifdef CONFIG_X86_RESERVE_LOW_64K
-static int __init dmi_low_memory_corruption(const struct dmi_system_id *d)
-{
-        printk(KERN_NOTICE
-                "%s detected: BIOS may corrupt low RAM, working around it.\n",
-                d->ident);
-
-        e820_update_range(0, 0x10000, E820_RAM, E820_RESERVED);
-        sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
-
-        return 0;
-}
-#endif
-
-/* List of systems that have known low memory corruption BIOS problems */
-static struct dmi_system_id __initdata bad_bios_dmi_table[] = {
-#ifdef CONFIG_X86_RESERVE_LOW_64K
-        {
-                .callback = dmi_low_memory_corruption,
-                .ident = "AMI BIOS",
-                .matches = {
-                        DMI_MATCH(DMI_BIOS_VENDOR, "American Megatrends Inc."),
-                },
-        },
-        {
-                .callback = dmi_low_memory_corruption,
-                .ident = "Phoenix BIOS",
-                .matches = {
-                        DMI_MATCH(DMI_BIOS_VENDOR, "Phoenix Technologies"),
-                },
-        },
-        {
-                .callback = dmi_low_memory_corruption,
-                .ident = "Phoenix/MSC BIOS",
-                .matches = {
-                        DMI_MATCH(DMI_BIOS_VENDOR, "Phoenix/MSC"),
-                },
-        },
-        /*
-         * AMI BIOS with low memory corruption was found on Intel DG45ID and
-         * DG45FC boards.
-         * It has a different DMI_BIOS_VENDOR = "Intel Corp.", for now we will
-         * match only DMI_BOARD_NAME and see if there is more bad products
-         * with this vendor.
-         */
-        {
-                .callback = dmi_low_memory_corruption,
-                .ident = "AMI BIOS",
-                .matches = {
-                        DMI_MATCH(DMI_BOARD_NAME, "DG45ID"),
-                },
-        },
-        {
-                .callback = dmi_low_memory_corruption,
-                .ident = "AMI BIOS",
-                .matches = {
-                        DMI_MATCH(DMI_BOARD_NAME, "DG45FC"),
-                },
-        },
-        /*
-         * The Dell Inspiron Mini 1012 has DMI_BIOS_VENDOR = "Dell Inc.", so
-         * match on the product name.
-         */
-        {
-                .callback = dmi_low_memory_corruption,
-                .ident = "Phoenix BIOS",
-                .matches = {
-                        DMI_MATCH(DMI_PRODUCT_NAME, "Inspiron 1012"),
-                },
-        },
-#endif
-        {}
-};
+static unsigned reserve_low = CONFIG_X86_RESERVE_LOW << 10;
 
 static void __init trim_bios_range(void)
 {
@@ -699,8 +627,14 @@ static void __init trim_bios_range(void)
          * A special case is the first 4Kb of memory;
          * This is a BIOS owned area, not kernel ram, but generally
          * not listed as such in the E820 table.
+         *
+         * This typically reserves additional memory (64KiB by default)
+         * since some BIOSes are known to corrupt low memory.  See the
+         * Kconfig help text for X86_RESERVE_LOW.
          */
-        e820_update_range(0, PAGE_SIZE, E820_RAM, E820_RESERVED);
+        e820_update_range(0, ALIGN(reserve_low, PAGE_SIZE),
+                          E820_RAM, E820_RESERVED);
+
         /*
          * special case: Some BIOSen report the PC BIOS
          * area (640->1Mb) as ram even though it is not.
@@ -710,6 +644,28 @@ static void __init trim_bios_range(void)
         sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
 }
 
+static int __init parse_reservelow(char *p)
+{
+        unsigned long long size;
+
+        if (!p)
+                return -EINVAL;
+
+        size = memparse(p, &p);
+
+        if (size < 4096)
+                size = 4096;
+
+        if (size > 640*1024)
+                size = 640*1024;
+
+        reserve_low = size;
+
+        return 0;
+}
+
+early_param("reservelow", parse_reservelow);
+
 /*
  * Determine if we were loaded by an EFI loader.  If so, then we have also been
  * passed the efi memmap, systab, etc., so we should use these data structures
@@ -865,8 +821,6 @@ void __init setup_arch(char **cmdline_p)
 
         dmi_scan_machine();
 
-        dmi_check_system(bad_bios_dmi_table);
-
         /*
          * VMware detection requires dmi to be available, so this
          * needs to be done after dmi_scan_machine, for the BP.