Reserve physical page

[Prateek Sharma]

On Sat, Aug 6, 2011 at 11:35 PM, Thayumanavar S <thayumker at gmail.com> wrote:

> > Hello everyone,
> >    I am wondering whether it is possible to reserve a particular physical
> > page in the kernel.
> > The GFP pages can start from _any_ location, and i cannot find a way to
> > specify a starting pfn.
> > I need a few dozen pages to store a bitmap starting at a particular
> physical
> > page frame number.
> >    Perhaps i am trying to do this wrong? I am trying to establish a
> > (one-way) communication between KVM and a guest VM, by assuming that if
> KVM
> > knows the physical address in the VM , it can access that bitmap.
>
> you can covert pa to pfn to struct page (there are some macros in the
> kernel that does this, you grep the kernel source for it) and directly
> set the PG_reserved flag of that struct page.
>
>
Ok. But in this case i have to ensure that the pfn is not mapped by the
kernel, right?
Will scanning mem_map to find such a pfn help?
I'm wondering if there are regions which are typically 'free' which i can
reserve and use.

Thanks for the reply,
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