Re: UEFI support in ARM DomUs

[Oleksandr Andrushchenko <andr2000@xxxxxxxxx>]

On 6/19/20 4:16 PM, Peng Fan wrote:
> > Subject: Re: UEFI support in ARM DomUs
> >
> >
> > On 6/19/20 3:59 PM, Julien Grall wrote:
> > > Hi,
> > >
> > > On 19/06/2020 13:51, Oleksandr Andrushchenko wrote:
> > > > On 6/19/20 3:47 PM, Julien Grall wrote:
> > > > > They will not be available from the fdt, but you can retrieve them with an
> > hypervisor call (see HVM_PARAM_STORE_PFN,
> > HVM_PARAM_CONSOLE_PFN).
> > > > Yes, and it used in the relevant pieces of code (hyp calls)
> > > > > One question though, why do you need to map them in advance?
> > Couldn't you map them on demand?
> > > > Well, we need to at least estimate the pg_table size so we can reserve and
> > allocate memory later,
> > > Oh, so U-boot doesn't support runtime page-table table allocation. Is that
> > right?
> > As per my understanding no, we provide a memory map and the tables are
> > allocated beforehand
> You are right.
ok, so then we only have a choice of probing the range via hyp calls
> Regards,
> Peng.
> > > > so I have to provide memory range from either by coding a constant or
> > looking into the devtree at
> > > > hypervisor { reg = <>; }. It is a bit tricky though
> > > Looking for a node in the device-tree shouldn't be too difficult given that you
> > have fdt_* available.
> > > However, please not that <reg> doesn't refer to the guest magic pages.
> > Instead, it provides a region you can use for mapping the grant-table frames
> >
> > Indeed, this is in my case 0x38000000, but the magic is at 0x39000000
> >
> > So, I need the memory range set up beforehand, but I can't as there is no cute
> > way to get that.
> >
> > Of course, I can issue a hyp call to get HVM_PARAM_CONSOLE_PFN and use it
> > as the base address,
> >
> > but this smells like a hack. I can call other HVM_PARAM_ to get their pfns and
> > set up the memory regions,
> >
> > but this looks a bit weird. I need that constant badly ;)
> >
> > > Cheers,