linux-kernel - Re: More e820 unification?

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Message-ID: <86802c440806021244u1c57f74dq9e581438f1365bbb@mail.gmail.com>
Date:	Mon, 2 Jun 2008 12:44:55 -0700
From:	"Yinghai Lu" <yhlu.kernel@...il.com>
To:	"Jeremy Fitzhardinge" <jeremy@...p.org>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>
Subject: Re: More e820 unification?

On Mon, Jun 2, 2008 at 12:24 PM, Jeremy Fitzhardinge <jeremy@...p.org> wrote:
> Yinghai Lu wrote:
>>
>> [PATCH] x86: cleanup max_pfn_mapped usage - 32bit
>> may need you update xen pv to specify max_pfn_mapped early stage...
>
> Ah, yes, I saw your mail.  What exactly does that value mean?  What should I
> set it to?

arch/x86/kernel/head_32.S doesn't know max_low_pfn yet, so it could
initialize initial_pg_table to cover much less of the max_low_pfn.
it will need paging_init/pagetable_init/kernel_phys... to initialize
mapping to max_low_pfn.
but that is too late. it said need to use alloc_bootmem_low_pages to
get bootmem, other wise even you can get it > mem_mapped, you can not
use.
two memory region must be get via find_e820_area even before bootmem is there.
bootmap for bootmem, and pgdat for node0 in numa_32. so it need to
take the really mapped as parameter for that func, instead of
max_low_pfn.

We can get the real max_pfn_mapped in head_32.S when finish the
initial page table.

for XEN PV, when you are preparing the init pg table in domain
builder, you should keep the max_pfn_mapped ...

64 bit doesn't need that, because it call init_memory_mapping very
earlier..., and it cover all memory.

YH
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