vmalloc size

[Subramaniam Appadodharana]

On Mon, Jun 25, 2012 at 3:00 PM, Dave Hylands <dhylands at gmail.com> wrote:

> Hi Subbu,
>
> On Mon, Jun 25, 2012 at 11:18 AM, Subramaniam Appadodharana
> <c.a.subramaniam at gmail.com> wrote:
> >
> >
> > On Mon, Jun 25, 2012 at 1:00 PM, Mulyadi Santosa <
> mulyadi.santosa at gmail.com>
> > wrote:
> >>
> >> Hi.... :)
> >>
> >> On Sun, Jun 24, 2012 at 1:32 AM, Subramaniam Appadodharana
> >> <c.a.subramaniam at gmail.com> wrote:
> >> > Hi All,
> >> > I am trying to understand how vmalloc memory is reserved in kernel. In
> >> > 3.4+
> >> > latest kernel, the default vmalloc size is 240MB.
> >>
> >> vmalloc reserved address range, you meant?
> >>
> >> >Is this a carveout from
> >> > the 1GiB memory that kernel has?
> >>
> >> Yup....
> >>
> >> > In other words can I do a __pa(VMALLOC_START) or __pa(VMALLOC_END)
> >> > or __pa(highmemory) irrespective of the vmalloc size that I request,
> say
> >> >  doing vmalloc=1G?
> >>
> >> uhm....not sure....vmalloc-ed is not physically contigous. Also, it is
> >> set up far after identity mapping setup. So, the value you get from
> >> __pa() IMHO would be likely invalid or has no meaning.
> >>
> > I thought that, as log as we know that the address is within  the 1GiB,
> we
> > could get the
> > pa of the virtual address using __pa(). Is this not the case?
>
> __pa only works on kernel direct addresses.
>
> __pa doesn't work on the addresses from vmalloc
>
> Using __pa on VMALLOC_START or VMALLOC_END doesn't really make sense.
> If there were any physical memory there, it would be highmem.
>
> Okay, but my intention was to just print out the pa for the VMALLOC_START
and END, just to know where they are.
And I thought they will work. no?

__pa should only be used on memory from PAGE_OFFSET through to (high_memory
> - 1)
>
> --
> Dave Hylands
> Shuswap, BC, Canada
> http://www.davehylands.com
>
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