From mboxrd@z Thu Jan  1 00:00:00 1970
From: orca.chen@gmail.com (Min-Hua Chen)
Date: Wed, 27 May 2015 22:23:01 +0800
Subject: physical memory userspace/kernel split on Linux x86-64
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Message-ID: <20150527142301.GA4358@debian777.Home>
To: kernelnewbies@lists.kernelnewbies.org
List-Id: kernelnewbies.lists.kernelnewbies.org

Hi,

Linux kernel basically manages all available physical memory pages.
If user-space need a page, kernel allocates a page for it. Hence a
physical page may be in mapped to user-space virtual address or 
kernel-space virtual address or both.

The user-space and kernel-space exist in virtual address space, not
physical.

Thanks,
Min-Hua

On Wed, May 27, 2015 at 09:12:11AM +0800, Le Tan wrote:
> Hi,
> Is there an explict split between userspace and kernel in physical
> memory on Linux x86-64? That is, given a physical address, can I tell
> whether this address is from userspace or not?
> As far as I know, in virtual address space, the kernel will use the
> upper half and the userspace will use the lower half. But what about
> in physical address space?
> 
> Thanks very much!
> 
> Le
> 
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