Xen on ARM: Read SP_usr and SP_svc in HYP mode

Xen on ARM: Read SP_usr and SP_svc in HYP mode

[harry]

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Hi,

Now I want to implement some functions in other hypervisor, so I need to read SP_usr and SP_svc in HYP mode. I know Xen has implemented this function. But I use it with regs->sp_usr/svc to achieve this. But I don't know how to achieve it. I have read the entry.S file and get the process to save the regs, but some definition is not clear. I want to know if there is some asm command to achieve this? Or do I need to switch the mode manually to read it?

Thanks and regards,
Harry

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Re: Xen on ARM: Read SP_usr and SP_svc in HYP mode

[Julien Grall]

On 25/08/15 05:43, harry wrote:
> Hi,

Hello,

> Now I want to implement some functions in other hypervisor, so I need to
> read SP_usr and SP_svc in HYP mode. I know Xen has implemented this
> function. But I use it with regs->sp_usr/svc to achieve this. But I
> don't know how to achieve it. I have read the entry.S file and get the
> process to save the regs, but some definition is not clear. I want to
> know if there is some asm command to achieve this? Or do I need to
> switch the mode manually to read it?

Please reach out the mailing list related to the hypervisor you want to
modify to know whether they have handy helpers to access SP_usr/SP_svc.

If not, I would advice you to read the ARM ARM in order to know how to
access banked registers, particularly the section "Encoding and use of
Banked register transfer instructions".

Regards,

-- 
Julien Grall

Re: Xen on ARM: Read SP_usr and SP_svc in HYP mode

[harry]

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Hi,


Thank you very much! I have got the answer, we can use MSR/MRS instructions to load/save these regs.


Thanks and regards,
Harry

At 2015-08-29 00:25:17, "Julien Grall" <julien.grall@citrix.com> wrote:
>On 25/08/15 05:43, harry wrote:
>> Hi,
>
>Hi,
>
>> Now I want to implement some functions in other hypervisor, so I need to
>> read SP_usr and SP_svc in HYP mode. I know Xen has implemented this
>> function. But I use it with regs->sp_usr/svc to achieve this. But I
>> don't know how to achieve it. I have read the entry.S file and get the
>> process to save the regs, but some definition is not clear. I want to
>> know if there is some asm command to achieve this? Or do I need to
>> switch the mode manually to read it?
>
>Please reach out the mailing list related to the hypervisor you want to
>modify to know whether they have handy helpers to access SP_usr/SP_svc.
>
>If not, I would advice you to read the ARM ARM in order to know how to
>access banked registers, particularly the section "Encoding and use of
>Banked register transfer instructions".
>
>Regards,
>
>-- 
>Julien Grall

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