Ingo Molnar wrote:
> * Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
>> On Sat, 18 Apr 2009, Ingo Molnar wrote:
>>> Am i missing something?
>> We also try to avoid random motherboard resources etc that aren't
>> reserved or documented by the BIOS. It's better to go into big
>> holes. It's also better to try to keep as close to the old
>> (tested) behavior.
>
> Yeah - i'm not suggesting any change in behavior, nor am i
> suggesting any risky behavior. The current code seems to work quite
> well.
>
> I'm just suggesting (maybe foolishly) that instead of having any
> gap-rounding logic at all, add artificial entries to the e820 map to
> 'extend' and round up any odd ending entries.
>
> I.e. explicitly manage all the 'hole' space to be nicely rounded and
> to be far away from any T-Seg or other sekrit motherboard resource
> danger area.
>
> We'd do this after PCI static allocations (so we dont ever stomp on
> real, known resources) but before PCI dynamic allocations.
>
> The e820 printout would look literally like this:
>
> BIOS-provided physical RAM map:
> BIOS-e820: 0000000000000000 - 000000000009fc00 (usable) 0.639 MB RAM
> BIOS-e820: 000000000009fc00 - 00000000000a0000 (reserved) 0.001 MB
> [ hole ] 0.250 MB
> BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved) 0.125 MB
> BIOS-e820: 0000000000100000 - 000000003ed94000 (usable) 1004.5 MB RAM
> BIOS-e820: 000000003ed94000 - 000000003ee4e000 (ACPI NVS) 0.7 MB
> BIOS-e820: 000000003ee4e000 - 000000003fea2000 (usable) 16.3 MB RAM
> BIOS-e820: 000000003fea2000 - 000000003fee9000 (ACPI NVS) 0.3 MB
> BIOS-e820: 000000003fee9000 - 000000003feed000 (usable) 0.15 MB RAM
> BIOS-e820: 000000003feed000 - 000000003feff000 (ACPI data 0.07 MB
> BIOS-e820: 000000003feff000 - 000000003ff00000 (usable) 0.004 MB RAM
> BIOS-e820: 000000003ff00000 - 0000000040000000 (guard) 1.0 MB
> [ hole ] 3072.0 MB
>
> The '(guard)' entry at the end i added above.
>
> This way we intentionally create a 'free physical address space'
> hole space that is the same as the rounding logic. No rounding
> needed anywhere - as all the remaining address space is well-rounded
> already. Plus we'd also _see_ all our rounding logic by looking at
> the '(guard)' entries.
>
> Or maybe there's some aspect of gap-rounding that cannot be
> expressed in such a static way?
>
please check following patch.
From: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
[PATCH] x86: reserve range near the ram -v2
some BIOS use ram near end, but don't state it, just try to reserve them
as RAM buffer
v2: make it in e820 table early instead of resource tree.
[Impact: protect stolen RAM]
Signed-off-by: Yinghai Lu <yinghai@xxxxxxxxxx>
---
arch/x86/include/asm/e820.h | 2 +
arch/x86/kernel/e820.c | 52 ++++++++++++++++++++++++++++++++++++++++++++
arch/x86/kernel/setup.c | 6 +++++
3 files changed, 60 insertions(+)
Index: linux-2.6/arch/x86/kernel/e820.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/e820.c
+++ linux-2.6/arch/x86/kernel/e820.c
@@ -150,6 +150,9 @@ static void __init e820_print_type(u32 t
case E820_UNUSABLE:
printk(KERN_CONT "(unusable)");
break;
+ case E820_RAM_BUFFER:
+ printk(KERN_CONT "(RAM buffer)");
+ break;
default:
printk(KERN_CONT "type %u", type);
break;
@@ -1314,6 +1317,54 @@ void __init finish_e820_parsing(void)
}
}
+/* How much should we pad RAM ending depending on where it is? */
+static unsigned long __init ram_alignment(resource_size_t pos)
+{
+ unsigned long mb = pos >> 20;
+
+ /* To 64kB in the first megabyte */
+ if (!mb)
+ return 64*1024;
+
+ /* To 1MB in the first 16MB */
+ if (mb < 16)
+ return 1024*1024;
+
+ /* To 32MB for anything above that */
+ return 32*1024*1024;
+}
+
+void __init e820_reserve_stolen_ram(void)
+{
+ int i;
+ int changed = 0;
+
+ /*
+ * Try to bump up RAM regions to reasonable boundaries to
+ * avoid stolen RAM
+ */
+ for (i = 0; i < e820.nr_map; i++) {
+ struct e820entry *entry = &e820_saved.map[i];
+ resource_size_t start, end;
+
+ if (entry->type != E820_RAM)
+ continue;
+ start = entry->addr + entry->size;
+ end = round_up(start, ram_alignment(start));
+ if (start == end)
+ continue;
+ e820_add_region(start, end - start, E820_RAM_BUFFER);
+ changed = 1;
+ }
+
+ if (!changed)
+ return;
+
+ sanitize_e820_map(e820.map, ARRAY_SIZE(e820.map), &e820.nr_map);
+ printk(KERN_INFO "fixed physical RAM map:\n");
+ e820_print_map("reserve_stolen_range");
+}
+
static inline const char *e820_type_to_string(int e820_type)
{
switch (e820_type) {
@@ -1322,6 +1373,7 @@ static inline const char *e820_type_to_s
case E820_ACPI: return "ACPI Tables";
case E820_NVS: return "ACPI Non-volatile Storage";
case E820_UNUSABLE: return "Unusable memory";
+ case E820_RAM_BUFFER: return "RAM Buffer";
default: return "reserved";
}
}
Index: linux-2.6/arch/x86/include/asm/e820.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/e820.h
+++ linux-2.6/arch/x86/include/asm/e820.h
@@ -44,6 +44,7 @@
#define E820_ACPI 3
#define E820_NVS 4
#define E820_UNUSABLE 5
+#define E820_RAM_BUFFER 6
/* reserved RAM used by kernel itself */
#define E820_RESERVED_KERN 128
@@ -78,6 +79,7 @@ extern u64 e820_update_range(u64 start,
extern u64 e820_remove_range(u64 start, u64 size, unsigned old_type,
int checktype);
extern void update_e820(void);
+extern void e820_reserve_stolen_ram(void);
extern void e820_setup_gap(void);
extern int e820_search_gap(unsigned long *gapstart, unsigned long *gapsize,
unsigned long start_addr, unsigned long long end_addr);
Index: linux-2.6/arch/x86/kernel/setup.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/setup.c
+++ linux-2.6/arch/x86/kernel/setup.c
@@ -812,6 +812,12 @@ void __init setup_arch(char **cmdline_p)
insert_resource(&iomem_resource, &data_resource);
insert_resource(&iomem_resource, &bss_resource);
+ /*
+ * some systems use end of ram to for acpi or video ram
+ * but doesn't state that in reserved in e820
+ * try to round of ram etc and reserve them
+ */
+ e820_reserve_stolen_ram();
#ifdef CONFIG_X86_32
if (ppro_with_ram_bug()) {
--
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