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 <jeremy@xensource.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: H. Peter Anvin <hpa@zytor.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Cc: Vivek Goyal <vgoyal@in.ibm.com>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>
Cc: Zachary Amsden <zach@vmware.com>
Cc: Andi Kleen <ak@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/arch/x86/boot/compressed/head_32.S b/arch/x86/boot/compressed/head_32.S
index f35ea2237522c0267139af7666e2875b571dd4b4..a0ae2e7f6cecbcf0c0311a0ce6029408fd350268 100644 (file)
--- a/arch/x86/boot/compressed/head_32.S
+++ b/arch/x86/boot/compressed/head_32.S
@@ -27,13 +27,22 @@
 #include <asm/segment.h>
 #include <asm/page.h>
 #include <asm/boot.h>
+#include <asm/asm-offsets.h>
 
 .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 1dc1e19c0a9f200fe11fd1a2f051896c8eddf54f..b74d60d1b2fa1329f6f28c434fc47445cb39ccb4 100644 (file)
--- 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 f3140e596d407d892eb75aa0c486bd7411e1dcb2..8353c81c41c02865384e227b24e4af8e0879bcee 100644 (file)
--- 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 39677965e161a124eb2b298f36e68b32fe015156..00b1c2c5645417c046c55408694554e792083aea 100644 (file)
--- 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 */