Messages in this thread Patch in this message | | | Date | Sat, 24 May 2008 10:49:51 +0100 | From | Jeremy Fitzhardinge <> | Subject | [PATCH] xen: boot via i386_start_kernel to get early reservations |
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Boot Xen via i386_start_kernel so that all the early reservations are made properly; without these, it will start using the kernel and pagetables as early heap memory, which is a bit suboptimal.
One tricky part is that reserve_early() will just panic if any of the early reservations overlap any others. When a Xen domain is built, it constructs the initial address space as:
kernel text+data+bss initrd initial pagetable
Therefore, when reserving the pagetable (from &_end to init_pg_tables_end), it covers the whole initrd area. If it then tries to reserve the initrd, it will panic because of the overlap.
The simple fix here is to reserve INIT_PG_TABLE first, and then only reserve the ramdisk if it doesn't overlap with the previous reservations. A better/more complex fix might be to make reserve_early() deal with overlapping reservations.
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com> --- arch/x86/kernel/head32.c | 6 ++++-- arch/x86/xen/enlighten.c | 2 +- include/asm-x86/setup.h | 1 + 3 files changed, 6 insertions(+), 3 deletions(-)
=================================================================== --- a/arch/x86/kernel/head32.c +++ b/arch/x86/kernel/head32.c @@ -66,6 +66,7 @@ void __init i386_start_kernel(void) void __init i386_start_kernel(void) { reserve_early(__pa_symbol(&_text), __pa_symbol(&_end), "TEXT DATA BSS"); + reserve_early(__pa_symbol(&_end), init_pg_tables_end, "INIT_PG_TABLE"); #ifdef CONFIG_BLK_DEV_INITRD /* Reserve INITRD */ @@ -73,10 +74,11 @@ void __init i386_start_kernel(void) u64 ramdisk_image = boot_params.hdr.ramdisk_image; u64 ramdisk_size = boot_params.hdr.ramdisk_size; u64 ramdisk_end = ramdisk_image + ramdisk_size; - reserve_early(ramdisk_image, ramdisk_end, "RAMDISK"); + if (ramdisk_end <= __pa_symbol(&_text) || + ramdisk_image > init_pg_tables_end) + reserve_early(ramdisk_image, ramdisk_end, "RAMDISK"); } #endif - reserve_early(__pa_symbol(&_end), init_pg_tables_end, "INIT_PG_TABLE"); reserve_ebda_region(); =================================================================== --- a/arch/x86/xen/enlighten.c +++ b/arch/x86/xen/enlighten.c @@ -1264,5 +1264,5 @@ asmlinkage void __init xen_start_kernel( } /* Start the world */ - start_kernel(); + i386_start_kernel(); } =================================================================== --- a/include/asm-x86/setup.h +++ b/include/asm-x86/setup.h @@ -58,6 +58,7 @@ int __init copy_e820_map(struct e820entr int __init copy_e820_map(struct e820entry *biosmap, int nr_map); void __init add_memory_region(unsigned long long start, unsigned long long size, int type); +void __init i386_start_kernel(void); extern unsigned long init_pg_tables_end;
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