Re: [Xen-devel] xen-kernel and EDD

[Lin-Bao Zhang <2004.zhang@xxxxxxxxx>]

2011/8/18 Lin-Bao Zhang <2004.zhang@xxxxxxxxx>
>
> 2011/8/18 Keir Fraser <keir@xxxxxxx>:
> > It's almost certainly this. In latest Xen we run the trampoline code at
> > 0x7c000. So you can try rebuilding your hypervisor with the following
> > changes:
> > 1. Change BOOT_TRAMPOLINE to 0x7c000
> > 2. In arch/x86/boot/head.S, change the line 'mov $0x98000,%esp' to 'mov
> > $0x80000,%esp'.
> >
> > That will probably fix your problem.
> >
> >  -- Keir

Hi Keir ,
maybe 0x80000 is not very good, I check xen-4.1.0 code:
/* Copy bootstrap trampoline to low memory, below 1MB. */
       mov     $sym_phys(trampoline_start),%esi
       mov     $bootsym_phys(trampoline_start),%edi
       mov     $trampoline_end - trampoline_start,%ecx
       rep     movsb

       mov     $bootsym_phys(early_stack),%esp  //eary_stack.
       call    cmdline_parse_early

       /* Jump into the relocated trampoline. */
       jmp     $BOOT_CS32,$bootsym_phys(trampoline_boot_cpu_entry)

it seems that direct number is not very compatible .

1, another point : it seems that this code should copy code (from
trampoline_start to trampoline_end) to BOOT_TRAMPOLINE(0x90000)) , I
will consider if trampoline code size bigger than
0x95400-0x90000=21KBytes .
but my binary xen.gz doesn't include symbols , so I can't see address
of trampoline_start and trampoline_end.  how to get them ? must
recompile it ?I think maybe redhat has deleted symbols . yet I don't
trampoline will be over 21KBytes,because it seems small code.


2, about definition of trampoline_start and trampoline_end ?
I just can see:
#define BOOT_TRAMPOLINE 0x90000
#define bootsym_phys(sym)                                 \
   (((unsigned long)&(sym)-(unsigned long)&trampoline_start)+BOOT_TRAMPOLINE)
#define bootsym(sym)                                      \
   (*RELOC_HIDE((typeof(&(sym)))__va(__pa(&(sym))),      \
                BOOT_TRAMPOLINE-__pa(trampoline_start)))
#ifndef __ASSEMBLY__
extern char trampoline_start[], trampoline_end[];
extern char trampoline_realmode_entry[];
extern unsigned int trampoline_xen_phys_start;
extern unsigned char trampoline_cpu_started;
#endif

。。。。。。。。。。
head.S :
       .globl trampoline_start, trampoline_end
trampoline_start:  //  it seems that I must find this symbol to
confirm its value , nm -a this file , displaying no symbols.
#include "trampoline.S"
trampoline_end:


3 , in sles11:

I find sles11 again , I did the same steps .
in sles11 x86_64 version ,there are also :
xen-syms-3.3.1_18546_12-3.1 and xen.gz :
nm -a xen(unzip xen.gz) ,can't trampoline_start/end
while nm -a xen-syms-3.3.1_18546_12-3.1 , I can finally find
"trampoline_start" and "trampoline_end" :
--bob comment: I begin another email subject "about __XEN_VIRT_START
and 0x100000" to ask the difference between these 2 files.

from this output ,useful information:
ffff828c80100000 A _start
...
ffff828c8020d5b6 t trampoline_boot_cpu_entry
ffff828c8020d549 T trampoline_cpu_started
ffff828c8020fe50 T trampoline_end                                 //here
ffff828c8020d511 t trampoline_gdt
ffff828c8020d54a t trampoline_protmode_entry
ffff828c8020d4e0 T trampoline_realmode_entry
ffff828c8020d4e0 T trampoline_start                                  //here
ffff828c8020d545 T trampoline_xen_phys_start
ffff828c80172ab0 t transition_pstate
...
from sles11 , trampoline code size   0xFFFF828C8_020FE50 -
ffff828c8_020d4e0 =  0x2970  (about 10KBytes)
if BOOT_TRAMPOLINE == 0x90000 , then trampoline end will be 0x92970
,while my EBDA is 0x954000 ~ 0xa0000 . so I think don't overlap.
certainly , this number is from sles11 xen-kernel ,but I think their
trampoline.S basily same ,length should be almost same.

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