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From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
To: Heiko Schumann <heiko.sirona@gmail.com>
Cc: linux-rt-users@vger.kernel.org
Subject: Re: Highmem support on ppc32 plattform with PREEMPT_RT_FULL option
Date: Fri, 31 May 2013 21:56:49 +0200	[thread overview]
Message-ID: <20130531195649.GB24632@linutronix.de> (raw)
In-Reply-To: <CAKQvxgWOcnK79bn1f0LWqvagAEXVrS39eGv0ESUvp4LwdnGEFw@mail.gmail.com>

* Heiko Schumann | 2013-05-14 13:04:34 [+0200]:

>Hello,
Hi,

>i´ve a ppc32 processor with 2 GB Ram. I use a 3.8.4 Kernel with vendor
>and 3.8.4rt2 patch. To support  2 GB of RAM i´ve to set the kernel
>option HIGHMEM. But this option is not available when PREEMPT_RT_FULL
>is selected.
>Is there a workaround or additional patch to use more than 1GB RAM on
>a ppc32 with the option PREEMPT_RT_FULL?

No, we have only arm and x86 so far. Either try to do the same thing on
Power that has been on ARM & x86.
A workaround would be to adjust lowmem, virtual base and user stack.
That means your userland wouldn't have 3GiB virtual address space but
the kernel could access 2GiB.
Something like 
  CONFIG_PAGE_OFFSET=0x40000000
  CONFIG_KERNEL_START=0x40000000
  CONFIG_TASK_SIZE=0x40000000

should work.

>
>Thanks

Sebatian
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      reply	other threads:[~2013-05-31 19:56 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-05-14 11:04 Highmem support on ppc32 plattform with PREEMPT_RT_FULL option Heiko Schumann
2013-05-31 19:56 ` Sebastian Andrzej Siewior [this message]

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