Re: [Xen-devel] [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space

[Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>]

On 07/12/2016 10:57 AM, Shannon Zhao wrote:
> On 2016年07月12日 22:50, Wei Liu wrote:
>> On Tue, Jul 12, 2016 at 10:42:07PM +0800, Shannon Zhao wrote:
>>>>>>>>>>>>>>>>>>>>>> Does it mean we would need to update the slack to take 
>>>>>>>>>>>>>>>>>>>>>> into account the ACPI
>>>>>>>>>>>>>>>>>>>>>> blob?
>>>>>>>>>>>>>> Yes, we need to take into account the ACPI blob. Probably not in 
>>>>>>>>>>>>>> the
>>>>>>>>>>>>>> slack but directly in mam_memkb.
>>>>>>>>>> Sorry, I'm not sure understand this. I found the b_info->max_memkb 
>>>>>>>>>> but
>>>>>>>>>> didn't find the slack you said. And how to fix this? Update
>>>>>>>>>> b_info->max_memkb or the slack?
>>>>>> Can you calculate the size of your payload and add that to max_memkb?
>>>>>>
>>>> Yeah, but the size will be changed if we change the tables in the future
>>>> and this also should consider x86, right?
>> That could easily be solved by introducing a function to calculate the
>> size, right?
> Oh, I'm not familiar with this. Let's clarify on this. It can add the
> size to max_memkb after generating the ACPI tables and before loading
> the tables to guest space and it doesn't have to add the size at
> libxl__domain_build_info_setdefault(), right?

This was discussed before: ACPI tables are part of RAM whose size is
specified by the config file (and is reflected in max_memkb I believe).
It may not be presented to the guest as RAM (i.e. on x86 it is labeled
by BIOS (or whoever) as a dedicated type in e820) but it still resides
in DIMMs.

I believe we should not increase memory resources for ACPI tables.

-boris





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