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Re: [Xen-devel] [PATCH v2 1/2] x86/dom0: rename paging function

On Thu, Dec 13, 2018 at 03:17:05AM -0700, Jan Beulich wrote:
> >>> On 13.12.18 at 10:14, <roger.pau@xxxxxxxxxx> wrote:
> > On Thu, Dec 13, 2018 at 12:45:07AM -0700, Jan Beulich wrote:
> >> >>> On 12.12.18 at 18:05, <roger.pau@xxxxxxxxxx> wrote:
> >> > On Wed, Dec 12, 2018 at 09:15:09AM -0700, Jan Beulich wrote:
> >> >> The MMIO side of things of course still remains unclear.
> >> > 
> >> > Right, for the MMIO and the handling of grant and foreign mappings it's
> >> > not clear how we want to proceed.
> >> > 
> >> > Maybe account for all host RAM (total_pages) plus MMIO BARs?
> >> 
> >> Well, I thought we've already settled on it being impossible to
> >> account for all MMIO BARs at this point.
> > 
> > Well, I could iterate over all the registered PCI devices and size
> > the BARs (without VF BARs at least initially). This is quite
> > cumbersome, my other option would be using max_page and hope that
> > there are enough holes to make up for BAR MMIO regions.
> Well, maybe we could live with this for now. I certainly would
> prefer to have a 3rd opinion though, as I continue to feel uneasy
> with this rather imprecise estimation (i.e. I'd much prefer a more
> dynamic / on-demand approach).

I agree it's not a perfect solution, but I think what's currently done
is even worse, and we already had bug reports of users seeing Xen
panic at PVH Dom0 build time if no dom0_mem parameter is specified.

Would you be OK with using max_page then? This is the less complex
option to implement ATM, and BAR sizing can be added later together
with a more dynamic p2m memory management.

Thanks, Roger.

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