On 12/23/2012 10:00 AM, Yinghai Lu wrote:
> On Sun, Dec 23, 2012 at 6:33 AM, H. Peter Anvin <[email protected]> wrote:
>> Explanation please?
>>
>
> you have following change in the patch
>
> /* Finally jump to run C code and to be on real kernel address
> * Since we are running on identity-mapped space we have to jump
> * to the full 64bit address, this is only possible as indirect
> * jump. In addition we need to ensure %cs is set so we make this
> - * a far return.
> + * a far jump.
> */
> - movq initial_code(%rip),%rax
> pushq $0 # fake return address to stop unwinder
> - pushq $__KERNEL_CS # set correct cs
> - pushq %rax # target address in negative space
> - lretq
> + /* gas 2.22 is buggy and mis-assembles ljmpq */
> + rex64 ljmp *initial_code(%rip)
>
> #ifdef CONFIG_HOTPLUG_CPU
> /*
>
> remove that change, AMD systems works again.
>
That is not an explanation.
-hpa
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