[PATCH v3 4/4] kexec, x86_64: Load bzImage64 above 4G

[Yinghai Lu]

On Wed, Nov 21, 2012 at 6:37 AM, Vivek Goyal <vgoyal at redhat.com> wrote:
> On Tue, Nov 20, 2012 at 11:31:38PM -0800, Yinghai Lu wrote:
>
> [..]
>> +     /* avoid cross GB boundary */
>> +     align = real_mode->kernel_alignment;
>> +     addr = locate_hole(info, size, align, 0x100000, -1, -1);
>> +     if (addr == ULONG_MAX)
>> +             die("can not load bzImage64");
>> +     /* same GB ? */
>> +     while ((addr >> 30) != ((addr + size - 1) >> 30)) {
>> +             addr = locate_hole(info, size, align, 0x100000,
>> +                              round_down(addr + size - 1, (1UL<<30)), -1);
>> +             if (addr == ULONG_MAX)
>> +                     die("can not load bzImage64");
>> +     }
>> +     dbgprintf("Found kernel buffer at %lx size %lx\n", addr, size);
>
> Where does this limitation of not loading kernel across GB boundary come
> from?

in kernel arch/x86/kernel/head_64.S

it only set first 1G ident mapping. and if it find that code is above
1G, it will set extra ident mapping
for new _text.._end.
To make checking and add extra mapping simple and also save two extra
pages for mapping.
Limit that _text.._end in them same GB range.

Thanks

Yinghai