Re: [Xen-devel] [PATCH v16 5/9] x86: change default load address from 1 MiB to 2 MiB

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 01.03.17 at 11:51, <daniel.kiper@xxxxxxxxxx> wrote:
> On Wed, Mar 01, 2017 at 03:34:47AM -0700, Jan Beulich wrote:
>> >>> On 01.03.17 at 11:13, <daniel.kiper@xxxxxxxxxx> wrote:
>> > On Wed, Mar 01, 2017 at 02:05:39AM -0700, Jan Beulich wrote:
>> >> >>> On 21.02.17 at 20:19, <daniel.kiper@xxxxxxxxxx> wrote:
>> >> > Subsequent patches introducing relocatable early boot code play with
>> >> > page tables using 2 MiB huge pages. If load address is not aligned at
>> >> > 2 MiB then code touching such page tables must have special cases for
>> >> > start and end of Xen image memory region. So, let's make life easier
>> >> > and move default load address from 1 MiB to 2 MiB. This way page table
>> >> > code will be nice and easy. Hence, there is a chance that it will be
>> >> > less error prone too... :-)))
>> >> >
>> >> > Additionally, drop first 2 MiB mapping from Xen image mapping.
>> >> > It is no longer needed.
>> >>
>> >> What about the memory allocated for it? Aiui at least in the xen.efi
>> >> case there would be a 2Mb chunk left unused, but also never freed.
>> >
>> > Memory is not allocated for it.
>>
>> Are you sure? Where would the PE32+ header live in that case?
> 
> Is the PE32+ header loaded into memory? I think that only code and data stuff
> is put there. Header is useful only for loader. Am I missing something?

I think EFI's loader simply follows Windows' one(s). And yes, the
headers can be useful - to the loader itself (albeit then the loader
assumes that no-one fiddles with them).

Jan


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