Re: [Xen-devel] [PATCH] docs/sphinx: How Xen Boots on x86

[Jan Beulich <jbeulich@xxxxxxxx>]

On 10.12.2019 10:55, Andrew Cooper wrote:
> On 10/12/2019 07:52, Jan Beulich wrote:
>> On 09.12.2019 17:42, Andrew Cooper wrote:
>>> On 09/12/2019 15:20, Jan Beulich wrote:
>>>> On 06.12.2019 20:34, Andrew Cooper wrote:
>>>>> +Objects
>>>>> +~~~~~~~
>>>>> +
>>>>> +To begin with, most object files are compiled and linked.  This includes 
>>>>> the
>>>>> +Multiboot 1 and 2 headers and entrypoints, including the Multiboot 2 
>>>>> tags for
>>>>> +EFI extensions.  When ``CONFIG_PVH_GUEST`` is selected at build time, 
>>>>> this
>>>>> +includes the PVH entrypoint and associated ELF notes.
>>>>> +
>>>>> +Depending on whether the compiler supports 
>>>>> ``__attribute__((__ms_abi__))`` or
>>>>> +not, either an EFI stub is included which nops/fails applicable setup 
>>>>> calls,
>>>>> +or full EFI support is included.
>>>> Perhaps also mention that the linker needs to support the necessary
>>>> binary output format? And perhaps "setup and runtime calls"?
>>> Link time behaviour is (deliberately) in a later section.
>> I realize(d) this, but the statement above is simply not true without
>> also mentioning required linker capabilities: The object files won't
>> have "full EFI support included" in this case. So I'd expect a "see
>> also" here at the very least.
> 
> Note how XEN_BUILD_EFI and XEN_BUILD_PE are different, one by compiler
> support for ms_abi, and one by linker support for i386pep.
> 
> Linker support for i386pep is not required at all to get EFI support in
> Xen.  This is how the MB2+EFI path is constructed.

Hmm, indeed. Meaning the build reporting "EFI support disabled" has
been wrong since the splitting of the two. Should now be something
like "Not generating xen.efi", I guess.

With the minor re-stating of 32-bit mode and the PE32+ naming
adjustment then
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Jan

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