Re: [PATCH] x86/pci: make pci_mem_start to be aligned only -v4

[Yinghai Lu]

Yinghai Lu wrote:
> 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()) {
> 

it seems ram_alignment is too aggressive, it eat some RAM really

[    0.000000] BIOS-provided physical RAM map:
[    0.000000]  BIOS-e820: 0000000000000000 - 0000000000097400 (usable)
[    0.000000]  BIOS-e820: 0000000000097400 - 00000000000a0000 (reserved)
[    0.000000]  BIOS-e820: 00000000000e0000 - 0000000000100000 (reserved)
[    0.000000]  BIOS-e820: 0000000000100000 - 00000000b7fa0000 (usable)
[    0.000000]  BIOS-e820: 00000000b7fae000 - 00000000b7fb0000 (usable)
[    0.000000]  BIOS-e820: 00000000b7fb0000 - 00000000b7fbe000 (ACPI data)
[    0.000000]  BIOS-e820: 00000000b7fbe000 - 00000000b7ff0000 (ACPI NVS)
[    0.000000]  BIOS-e820: 00000000b7ff0000 - 00000000b8000000 (reserved)
[    0.000000]  BIOS-e820: 00000000e0000000 - 00000000f0000000 (reserved)
[    0.000000]  BIOS-e820: 00000000fec00000 - 00000000fec01000 (reserved)
[    0.000000]  BIOS-e820: 00000000fee00000 - 00000000fef00000 (reserved)
[    0.000000]  BIOS-e820: 00000000ff700000 - 0000000100000000 (reserved)
[    0.000000]  BIOS-e820: 0000000100000000 - 0000002048000000 (usable)
[    0.000000] Early serial console at I/O port 0x3f8 (options '115200n8')
[    0.000000] console [uart0] enabled
[    0.000000] DMI present.
[    0.000000] fixed physical RAM map:
[    0.000000]  reserve_stolen_range: 0000000000000000 - 0000000000097400 (usable)
[    0.000000]  reserve_stolen_range: 0000000000097400 - 00000000000a0000 (RAM buffer)
[    0.000000]  reserve_stolen_range: 00000000000e0000 - 0000000000100000 (reserved)
[    0.000000]  reserve_stolen_range: 0000000000100000 - 00000000b7fa0000 (usable)
[    0.000000]  reserve_stolen_range: 00000000b7fa0000 - 00000000b8000000 (RAM buffer)
[    0.000000]  reserve_stolen_range: 00000000e0000000 - 00000000f0000000 (reserved)
[    0.000000]  reserve_stolen_range: 00000000fec00000 - 00000000fec01000 (reserved)
[    0.000000]  reserve_stolen_range: 00000000fee00000 - 00000000fef00000 (reserved)
[    0.000000]  reserve_stolen_range: 00000000ff700000 - 0000000100000000 (reserved)
[    0.000000]  reserve_stolen_range: 0000000100000000 - 0000002048000000 (usable)

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