On Fri, Jun 20, 2008 at 05:57:00PM +0200, Bernhard Walle wrote:
> This patch brings back limiting of the E820 map when a user-defined
> E820 map is specified. While the behaviour of i386 (32 bit) was to limit
> the E820 map (and /proc/iomem), the behaviour of x86-64 (64 bit) was not to
> limit.
>
> That patch limits the E820 map again for both x86 architectures.
>
> Code was tested for compilation and booting on a 32 bit and 64 bit system.
>
>
> Signed-off-by: Bernhard Walle <bwalle at suse.de>
> ---
> arch/x86/kernel/e820.c | 30 ++++++++++++++++++++++++++++++
> 1 files changed, 30 insertions(+), 0 deletions(-)
>
> diff --git a/arch/x86/kernel/e820.c b/arch/x86/kernel/e820.c
> index f5b1736..2e7d385 100644
> --- a/arch/x86/kernel/e820.c
> +++ b/arch/x86/kernel/e820.c
> @@ -934,6 +934,33 @@ static void early_panic(char *msg)
> panic(msg);
> }
>
> +void __init e820_limit_regions(unsigned long long size)
> +{
> + unsigned long long current_addr;
> + int i;
> +
> + for (i = 0; i < e820.nr_map; i++) {
> + current_addr = e820.map[i].addr + e820.map[i].size;
> + if (current_addr < size)
> + continue;
> +
> + if (e820.map[i].type != E820_RAM)
> + continue;
> +
> + if (e820.map[i].addr >= size) {
> + /*
> + * This region starts past the end of the
> + * requested size, skip it completely.
> + */
> + e820.nr_map = i;
> + } else {
> + e820.nr_map = i + 1;
> + e820.map[i].size -= current_addr - size;
> + }
> + return;
> + }
> +}
> +
> /* "mem=nopentium" disables the 4MB page tables. */
> static int __init parse_memopt(char *p)
> {
> @@ -951,6 +978,8 @@ static int __init parse_memopt(char *p)
>
> mem_size = memparse(p, &p);
> end_user_pfn = mem_size>>PAGE_SHIFT;
> + e820_limit_regions(mem_size);
> +
> return 0;
> }
> early_param("mem", parse_memopt);
> @@ -995,6 +1024,7 @@ static int __init parse_memmap_opt(char *p)
> e820_add_region(start_at, mem_size, E820_RESERVED);
> } else {
> end_user_pfn = (mem_size >> PAGE_SHIFT);
> + e820_limit_regions(mem_size);
> }
Hi Bernhard,
Just curious, when do we hit this bottom else condition?
In Documentation/kernel-parameters.txt file, I see, there are four
types of memmap= options. "exactmap" "@" "#" and "$". In the code
above we have already parsed all these option. So default condition
should be an error. Instead we seem to be limiting the memory size,
(something done by mem= parameter)..
Thanks
Vivek
