ARM-Xen customization of stage two translation.

ARM-Xen customization of stage two translation.

[Mazen Ezzeddine (Student)]

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Dear all,


I am using hardware assisted XEN on ARM cortex A-15, could you please hint me on the below:


I want the stage two translation from IPA to PA through the stage two translation  to  exclude a particular small contiguous region (some physical frames) of the physical memory ? is this achievable? could you please hint me on how can I accomplish?


Please share your experience experts.


Thank you so much.

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Re: ARM-Xen customization of stage two translation.

[Julien Grall]

On 20/05/15 09:39, Mazen Ezzeddine (Student) wrote:
> Dear all,

Hello,

> I am using hardware assisted XEN on ARM cortex A-15, could you please
> hint me on the below:
> 
> 
> I want the stage two translation from IPA to PA through the stage two
> translation  to  exclude a particular small contiguous region (some
> physical frames) of the physical memory ? is this achievable? could you
> please hint me on how can I accomplish?
> 

Is this physical region belong to the RAM or a device?

Regards,

-- 
Julien Grall

Re: ARM-Xen customization of stage two translation.

[Julien Grall]

Hello,

Please keep xen-devel CCed and avoid to top-post.

On 20/05/15 12:47, Mazen Ezzeddine (Student) wrote:
> Thanks Jlien,
> 
> Mainly it belongs to a device. I can't see why it would be problematic for a device and not for RAM or vice-versa? could you please hint me on what is the difference?

Because you have to do it differently.

For avoiding DOM0 to use a device, you can blacklist it per platform
(see blacklist_dev xen/arch/arm/platforms/vexpress.c). While for the RAM
you can update your device tree (see /memreserve/).

Regards,

-- 
Julien Grall

Re: ARM-Xen customization of stage two translation.

[Mazen Ezzeddine (Student)]

Thanks so much.

I will ensure to keep xen-devel cced and avoid top-post. Sorry and thanks for notifying me. 

However, my use-case will involve a scenario where the the page frames excluded from the second stage translation are to be allocated on the fly (through a slightly modified second stage translation) to a special guest when scheduled. Does mreserve work in such scenario? 


Best regards,

Re: ARM-Xen customization of stage two translation.

[Julien Grall]

On 20/05/15 13:05, Mazen Ezzeddine (Student) wrote:
> 
> Thanks so much.
> 
> I will ensure to keep xen-devel cced and avoid top-post. Sorry and thanks for notifying me. 
> 
> However, my use-case will involve a scenario where the the page frames excluded from the second stage translation are to be allocated on the fly (through a slightly modified second stage translation) to a special guest when scheduled. Does mreserve work in such scenario? 

Give a look to {,un}map_mmio_regions and
guest_physmap_add_entry/guest_physmap_remove_page in xen/arch/arm/p2m.c

regards,


-- 
Julien Grall