Re: [1/8,v3] NUMA Hotplug Emulator: add function to hide memory region via e820 table.

David Rientjes
2010-11-17T08:16:45Z

On Wed, 17 Nov 2010, shaohui.zheng@intel.com wrote:

> Index: linux-hpe4/arch/x86/kernel/e820.c
> ===================================================================
> --- linux-hpe4.orig/arch/x86/kernel/e820.c 2010-11-15 17:13:02.483461667 +0800
> +++ linux-hpe4/arch/x86/kernel/e820.c 2010-11-15 17:13:07.083461581 +0800
> @@ -971,6 +971,7 @@
> }
>
> static int userdef __initdata;
> +static u64 max_mem_size __initdata = ULLONG_MAX;
>
> /* "mem=nopentium" disables the 4MB page tables. */
> static int __init parse_memopt(char *p)
> @@ -989,12 +990,28 @@
>
> userdef = 1;
> mem_size = memparse(p, &p);
> - e820_remove_range(mem_size, ULLONG_MAX - mem_size, E820_RAM, 1);
> + e820_remove_range(mem_size, max_mem_size - mem_size, E820_RAM, 1);
> + max_mem_size = mem_size;
>
> return 0;
> }

This needs memmap= support as well, right?

> early_param("mem", parse_memopt);
>
> +#ifdef CONFIG_NODE_HOTPLUG_EMU
> +u64 __init e820_hide_mem(u64 mem_size)
> +{
> + u64 start, end_pfn;
> +
> + userdef = 1;
> + end_pfn = e820_end_of_ram_pfn();
> + start = (end_pfn << PAGE_SHIFT) - mem_size;
> + e820_remove_range(start, max_mem_size - start, E820_RAM, 1);
> + max_mem_size = start;
> +
> + return start;
> +}
> +#endif

This doesn't have any sanity checking for whether e820_remove_range() will
leave any significant amount of memory behind so the kernel will even boot
(probably should have a guaranteed FAKE_NODE_MIN_SIZE left behind?).

> +
> static int __init parse_memmap_opt(char *p)
> {
> char *oldp;