Re: [RFC PATCH] xen/memory: Introduce a hypercall to provide unallocated space

[Oleksandr <olekstysh@xxxxxxxxx>]

On 10.08.21 19:28, Julien Grall wrote:

Hi Julien.

> On 09/08/2021 22:18, Oleksandr wrote:
> > On 09.08.21 23:45, Julien Grall wrote:
> >
> >
> > Hi Julien
>
> Hi Oleksandr,
>
> > > On 09/08/2021 19:24, Oleksandr wrote:
> > > > On 09.08.21 18:42, Julien Grall wrote:
> > > > 1. If IOMMU is enabled for Dom0 -> provide holes found in Host DT 
> > > > as safe ranges
> > > > I would take into the account holes >= 1MB.
> > > May I ask why 1MB?
> > Nothing special, just thinking to not bother with small regions which 
> > would not be too useful overall, but could bloat resulting reg property.
> > Anyway, I would be ok with any sizes.
> I was more interesting with the reasoning behind your choice rather 
> than saying we want more.
> I agree that we may want to skip smaller region. I am guess that an 
> high number of small regions will also increase the bookeeping in Linux.
> But I would probably suggest to align the safe region to a 2MB 
> (superpage for 4KB page granularity) just because the backend (or even 
> Xen) may be able to do some optimization there.
OK, agree regarding the alignment. But, what about the size? I assume, 
it should be a multiple of 2MB.

> Cheers,
--
Regards,

Oleksandr Tyshchenko