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Re: Why "high memory" in x86?

>
> If the kernel wants to access the high memory, it will map it into the
> virtual address space of the KERNEL (3GB -> 4GB), right? Now at this
> point, what will happen to the original (identity) mapping of that
> kernel virtual memory address (to which it has now mapped the high
> memory)?
>
> TIA,
>
> Rajat
>
That is why kernel does not access the whole 1 GB, it's only 896MB, the rest
of the 128MB is used to create temp page table entries for the high mem.
e.g. if you have 2 GB of ram, then the 896 MB will be identity mapped while
for the rest 1GB + 128MB we will use the 128 MB kernel address space for
accessing the "high memory".


Oh, so you mean to say that the physical memory between 896MB and 1GB
is used to store the page tables and the memory map. But the
corresponding virtual memory addresses (~3.8 GB -> 4 GB) are used to
map high memory physical addresses?

Thanks,

Dan

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