> Jeremy Fitzhardinge wrote:
>
>> Mike Travis wrote:
>>
>>> Ingo Molnar wrote:
>>>
>>>
>>>> * Mike Travis <travis@sgi.com> wrote:
>>>>
>>>>
>>>>
>>>>> * Declare the pda as a per cpu variable.
>>>>>
>>>>> * Make the x86_64 per cpu area start at zero.
>>>>>
>>>>> * Since the pda is now the first element of the per_cpu area,
>>>>> cpu_pda()
>>>>> is no longer needed and per_cpu() can be used instead. This
>>>>> also makes
>>>>> the _cpu_pda[] table obsolete.
>>>>>
>>>>> * Since %gs is pointing to the pda, it will then also point to the
>>>>> per cpu
>>>>> variables and can be accessed thusly:
>>>>>
>>>>> %gs:[&per_cpu_xxxx - __per_cpu_start]
>>>>>
>>>>> Based on linux-2.6.tip
>>>>>
>>>>>
>>>> -tip testing found an instantaneous reboot crash on 64-bit x86, with
>>>> this config:
>>>>
>>>>
http://redhat.com/~mingo/misc/config-Thu_Jun__5_11_43_51_CEST_2008.bad
>>>>
>>>>
>>> I'm still stuck on this one. One new development is that the current
>>> -tip
>>> branch without the patches boots to the kernel prompt then hangs after
>>> a few
>>> moments and then reboots. It seems you can tickle it using ^C to abort a
>>> process.
>>>
>> Hi Mike,
>>
>> I added some instrumentation to Xen to print the cpu state on
>> triple-fault, which highlights an obvious-looking problem.
>>
>> (XEN) hvm.c:767:d1 Triple fault on VCPU0 - invoking HVM system reset.
>> (XEN) ----[ Xen-3.3-unstable x86_64 debug=y Not tainted ]----
>> (XEN) CPU: 1
>> (XEN) RIP: 0010:[<ffffffff80200160>]
>> (XEN) RFLAGS: 0000000000010002 CONTEXT: hvm
>> (XEN) rax: 0000000000000018 rbx: 0000000000000000 rcx: 00000000c0000080
>> (XEN) rdx: 0000000000000000 rsi: 0000000000092f40 rdi: 0000000020100800
>> (XEN) rbp: 0000000000000000 rsp: ffffffff807dfff8 r8: 0000000000208000
>> (XEN) r9: 0000000000000000 r10: 0000000000000000 r11: 00000000000000de
>> (XEN) r12: 0000000000000000 r13: 0000000000000000 r14: 0000000000000000
>> (XEN) r15: 0000000000000000 cr0: 0000000080050033 cr4: 00000000000000a0
>> (XEN) cr3: 0000000000201000 cr2: 0000000000000000
>> (XEN) ds: 0000 es: 0000 fs: 0000 gs: 0000 ss: 0000 cs: 0010
>>
>> The rip is:
>>
>> (gdb) x/i 0xffffffff80200160
>> 0xffffffff80200160 <secondary_startup_64+96>: movl %eax,%ds
>>
>> which is:
>>
>> lgdt early_gdt_descr(%rip)
>>
>> /* set up data segments. actually 0 would do too */
>> movl $__KERNEL_DS,%eax
>> movl %eax,%ds
>> movl %eax,%ss
>> movl %eax,%es
>>
>> And early_gdt_descr is:
>>
>> .globl early_gdt_descr
>> early_gdt_descr:
>> .word GDT_ENTRIES*8-1
>> .quad per_cpu__gdt_page
>>
>> and per_cpu__gdt_page is zero-based, and therefore not a directly
>> addressable symbol.
>>
>> I tried this patch, but it didn't work. Perhaps I'm missing something.
>>
>> diff -r bf5a46e13f78 arch/x86/kernel/head_64.S
>> --- a/arch/x86/kernel/head_64.S Tue Jun 17 22:10:51 2008 -0700
>> +++ b/arch/x86/kernel/head_64.S Wed Jun 18 10:34:24 2008 -0700
>> @@ -94,6 +94,8 @@
>>
>> addq %rbp, level2_fixmap_pgt + (506*8)(%rip)
>>
>> + addq $__per_cpu_load, early_gdt_descr+2(%rip)
>> +
>> /* Add an Identity mapping if I am above 1G */
>> leaq _text(%rip), %rdi
>> andq $PMD_PAGE_MASK, %rdi
>>
>>
>> J
>>
>
> Hi Jeremy,
>
> I'm not finding that code in the tip/latest or linux-next branches... ?
>
