From a24e785111a32ccb7cebafd24b1b1cb474ea8e5d Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Sun, 21 Oct 2007 16:41:35 -0700 Subject: [PATCH] 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/boot/compressed/head_32.S | 15 ++++++++-- arch/x86/boot/compressed/misc_32.c | 3 ++ arch/x86/boot/header.S | 7 ++++- arch/x86/kernel/head_32.S | 44 ++++++++++++++++++++++++++++-- 4 files changed, 63 insertions(+), 6 deletions(-) diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S index f35ea22375..a0ae2e7f6c 100644 --- a/arch/x86/boot/compressed/head_32.S +++ b/arch/x86/boot/compressed/head_32.S @@ -27,13 +27,22 @@ #include #include #include +#include .section ".text.head","ax",@progbits .globl startup_32 startup_32: - cld - cli + /* 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 + +1: cli movl $(__BOOT_DS),%eax movl %eax,%ds movl %eax,%es @@ -41,6 +50,8 @@ startup_32: movl %eax,%gs movl %eax,%ss +2: cld + /* Calculate the delta between where we were compiled to run * at and where we were actually loaded at. This can only be done * with a short local call on x86. Nothing else will tell us what diff --git a/arch/x86/boot/compressed/misc_32.c b/arch/x86/boot/compressed/misc_32.c index 1dc1e19c0a..b74d60d1b2 100644 --- a/arch/x86/boot/compressed/misc_32.c +++ b/arch/x86/boot/compressed/misc_32.c @@ -247,6 +247,9 @@ static void putstr(const char *s) int x,y,pos; char c; + if (RM_SCREEN_INFO.orig_video_mode == 0 && lines == 0 && cols == 0) + return; + x = RM_SCREEN_INFO.orig_x; y = RM_SCREEN_INFO.orig_y; diff --git a/arch/x86/boot/header.S b/arch/x86/boot/header.S index f3140e596d..8353c81c41 100644 --- a/arch/x86/boot/header.S +++ b/arch/x86/boot/header.S @@ -119,7 +119,7 @@ _start: # Part 2 of the header, from the old setup.S .ascii "HdrS" # header signature - .word 0x0206 # header version number (>= 0x0105) + .word 0x0207 # header version number (>= 0x0105) # or else old loadlin-1.5 will fail) .globl realmode_swtch realmode_swtch: .word 0, 0 # default_switch, SETUPSEG @@ -214,6 +214,11 @@ cmdline_size: .long COMMAND_LINE_SIZE-1 #length of the command line, #added with boot protocol #version 2.06 +hardware_subarch: .long 0 # subarchitecture, added with 2.07 + # default to 0 for normal x86 PC + +hardware_subarch_data: .quad 0 + # End of setup header ##################################################### .section ".inittext", "ax" diff --git a/arch/x86/kernel/head_32.S b/arch/x86/kernel/head_32.S index 39677965e1..00b1c2c564 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 */ -- 2.39.5