linux-kernel - Re: [PATCH v2 12/16] ARM: Xen: Document UEFI support on Xen ARM virtual platforms

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Message-ID: <569E3D9F.6050808@linaro.org>
Date:	Tue, 19 Jan 2016 21:43:59 +0800
From:	Shannon Zhao <shannon.zhao@...aro.org>
To:	Mark Rutland <mark.rutland@....com>,
	Stefano Stabellini <stefano.stabellini@...citrix.com>,
	ard.biesheuvel@...aro.org, leif.lindholm@...aro.org
CC:	Shannon Zhao <zhaoshenglong@...wei.com>,
	linux-arm-kernel@...ts.infradead.org,
	stefano.stabellini@...rix.com, david.vrabel@...rix.com,
	catalin.marinas@....com, will.deacon@....com,
	julien.grall@...rix.com, xen-devel@...ts.xen.org,
	devicetree@...r.kernel.org, linux-efi@...r.kernel.org,
	linux-kernel@...r.kernel.org, peter.huangpeng@...wei.com,
	Jan Beulich <JBeulich@...ell.com>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: Re: [PATCH v2 12/16] ARM: Xen: Document UEFI support on Xen ARM virtual
 platforms



On 2016/1/19 21:13, Mark Rutland wrote:
> On Tue, Jan 19, 2016 at 12:23:17PM +0000, Stefano Stabellini wrote:
>> >On Tue, 19 Jan 2016, Mark Rutland wrote:
>>> > >On Tue, Jan 19, 2016 at 06:25:25PM +0800, Shannon Zhao wrote:
>>>>>> > > > >>We don't do this in Documentation/arm/uefi.txt, and I don't see why we
>>>>>> > > > >>should do so here.
>>>>>> > > > >>
>>>>>> > > > >>Does Xen handle arbitrary size memory map descriptors? I'm not sure what
>>>>>> > > > >>new information might be passed in future additions to the descriptor
>>>>>> > > > >>format, and I'm not sure what should happen in the Dom0 case.
>>>>> > > > >
>>>>> > > > >Xen passes to Dom0 the memory map in the same format as the native
>>>>> > > > >memory map.
>>> > >
>>> > >Does Xen parse or modify the EFI memory map in any way?
>> >
>> >Xen:
>> >- calls EFI_BOOT_SERVICES.GetMemoryMap()
>> >- takes note of the memory regions for its own usage
>> >- create the fdt notes, including efi-mmap-start, with a pointer to it
>> >
>> >
>>> > >Does it pass the raw values returned by EFI_BOOT_SERVICES.GetMemoryMap()
>>> > >through to the xen,uefi-* properties, or does is make any static
>>> > >assumptions about what the values will be?
>> >
>> >It just passes the raw values.
> I take it that means that any memory carved out for Xen itself is
> described/discovered via a separate mechanism? How does that work

For Xen hypervisor booting on UEFI, it get the EFI memory map through 
the similar way like Linux, e.g. call EFI_BOOT_SERVICES.GetMemoryMap().
For Dom0, Xen will create a new EFI memory map for Dom0.

See [PATCH v3 52/62] arm/acpi: Prepare EFI memory descriptor for Dom0
http://lists.xen.org/archives/html/xen-devel/2015-11/msg01884.html

Thanks,
-- 
Shannon