Re: UEFI support in ARM DomUs

From: Julien Grall <julien@xen.org>
To: Oleksandr Andrushchenko <Oleksandr_Andrushchenko@epam.com>,
	Julien Grall <julien.grall.oss@gmail.com>,
	Stefano Stabellini <sstabellini@kernel.org>
Cc: Anastasiia Lukianenko <Anastasiia_Lukianenko@epam.com>,
	Juergen Gross <jgross@suse.com>, Peng Fan <peng.fan@nxp.com>,
	Roman Shaposhnik <roman@zededa.com>,
	Bertrand Marquis <Bertrand.Marquis@arm.com>,
	Nataliya Korovkina <malus.brandywine@gmail.com>,
	Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: UEFI support in ARM DomUs
Date: Fri, 19 Jun 2020 13:59:31 +0100	[thread overview]
Message-ID: <d7334aea-363e-49f6-f8c3-336e3c20eb0f@xen.org> (raw)
In-Reply-To: <ebf32205-55b0-8a40-1935-d3591be058ce@epam.com>

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?

> 
> 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

Cheers,

-- 
Julien Grall