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

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Jul 12, 2016 at 11:08:47AM -0400, Boris Ostrovsky wrote:
> 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?
> 

Hmm... I would like to think a bit more about this. But before dwelling
on this too much...

> 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.
> 

This is an interesting point. If there is already such resolution I will
be happy to follow it.

Any reference?

Wei.

> -boris
> 
> 
> 
> 

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