From a24e785111a32ccb7cebafd24b1b1cb474ea8e5d Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Sun, 21 Oct 2007 16:41:35 -0700 Subject: i386: paravirt boot sequence This patch uses the updated boot protocol to do paravirtualized boot. If the boot version is >= 2.07, then it will do two things: 1. Check the bootparams loadflags to see if we should reload the segment registers and clear interrupts. This is appropriate for normal native boot and some paravirtualized environments, but inapproprate for others. 2. Check the hardware architecture, and dispatch to the appropriate kernel entrypoint. If the bootloader doesn't set this, then we simply do the normal boot sequence. Signed-off-by: Jeremy Fitzhardinge Signed-off-by: Rusty Russell Acked-by: H. Peter Anvin Cc: "Eric W. Biederman" Cc: Vivek Goyal Cc: James Bottomley Cc: Zachary Amsden Cc: Andi Kleen Cc: Thomas Gleixner Cc: Ingo Molnar Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- arch/x86/kernel/head_32.S | 44 +++++++++++++++++++++++++++++++++++++++++--- 1 file changed, 41 insertions(+), 3 deletions(-) (limited to 'arch/x86/kernel/head_32.S') diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 39677965e161..00b1c2c56454 100644 --- a/arch/x86/kernel/head_32.S +++ b/arch/x86/kernel/head_32.S @@ -79,22 +79,30 @@ INIT_MAP_BEYOND_END = BOOTBITMAP_SIZE + (PAGE_TABLE_SIZE + ALLOCATOR_SLOP)*PAGE_ */ .section .text.head,"ax",@progbits ENTRY(startup_32) + /* check to see if KEEP_SEGMENTS flag is meaningful */ + cmpw $0x207, BP_version(%esi) + jb 1f + + /* test KEEP_SEGMENTS flag to see if the bootloader is asking + us to not reload segments */ + testb $(1<<6), BP_loadflags(%esi) + jnz 2f /* * Set segments to known values. */ - cld - lgdt boot_gdt_descr - __PAGE_OFFSET +1: lgdt boot_gdt_descr - __PAGE_OFFSET movl $(__BOOT_DS),%eax movl %eax,%ds movl %eax,%es movl %eax,%fs movl %eax,%gs +2: /* * Clear BSS first so that there are no surprises... - * No need to cld as DF is already clear from cld above... */ + cld xorl %eax,%eax movl $__bss_start - __PAGE_OFFSET,%edi movl $__bss_stop - __PAGE_OFFSET,%ecx @@ -128,6 +136,35 @@ ENTRY(startup_32) movsl 1: +#ifdef CONFIG_PARAVIRT + cmpw $0x207, (boot_params + BP_version - __PAGE_OFFSET) + jb default_entry + + /* Paravirt-compatible boot parameters. Look to see what architecture + we're booting under. */ + movl (boot_params + BP_hardware_subarch - __PAGE_OFFSET), %eax + cmpl $num_subarch_entries, %eax + jae bad_subarch + + movl subarch_entries - __PAGE_OFFSET(,%eax,4), %eax + subl $__PAGE_OFFSET, %eax + jmp *%eax + +bad_subarch: +WEAK(lguest_entry) +WEAK(xen_entry) + /* Unknown implementation; there's really + nothing we can do at this point. */ + ud2a +.data +subarch_entries: + .long default_entry /* normal x86/PC */ + .long lguest_entry /* lguest hypervisor */ + .long xen_entry /* Xen hypervisor */ +num_subarch_entries = (. - subarch_entries) / 4 +.previous +#endif /* CONFIG_PARAVIRT */ + /* * Initialize page tables. This creates a PDE and a set of page * tables, which are located immediately beyond _end. The variable @@ -140,6 +177,7 @@ ENTRY(startup_32) */ page_pde_offset = (__PAGE_OFFSET >> 20); +default_entry: movl $(pg0 - __PAGE_OFFSET), %edi movl $(swapper_pg_dir - __PAGE_OFFSET), %edx movl $0x007, %eax /* 0x007 = PRESENT+RW+USER */ -- cgit v1.2.3-59-g8ed1b