(no subject)

[Sanket Rathi]

I just want to know how can we restrict the maximum virtual memory and
maximum physical memory on ia64 platform.
Is there any settings in kernel so that we can change that and recompile
kernel. Actually we have a device which can only access 44 bits so we cant
I just want to know how can we restrict the maximum virtual memory and
maximum physical memory on ia64 platform.
Is there any settings in kernel so that we can change that and recompile
kernel. Actually we have a device which can only access 44 bits so we cant
have 64 bit address. I mean is it possible to discard some bits which are
not significant.

Tell me something related to this or any link which i can refer

Thanks in advance

--- Sanket Rathi

--------------------------

Re: your mail

[Alan Cox]

> I just want to know how can we restrict the maximum virtual memory and
> maximum physical memory on ia64 platform.
> kernel. Actually we have a device which can only access 44 bits so we cant

That won't help you. You might not be dealing with RAM at the bottom of the
address space. You might also be in platforms with an iommu, or doing DMA
to another PCI target

> Tell me something related to this or any link which i can refer

Assuming the device is doing bus mastering. Read
Documentation/DMA-mapping.txt

Re: your mail

[Sanket Rathi]

No actually i don't want that for DMA it is for diffrent requirment.
actually in our device there is a page table in device which have
virtual to physical address translation we save virtual address in device
and corresponding physical address. but we can store only upto 44 bit 
information of virtual address thats why i want that.

Can you help me in this 

Thanks in advance

-----
--------Sanket


> > I just want to know how can we restrict the maximum virtual memory and
> > maximum physical memory on ia64 platform.
> > kernel. Actually we have a device which can only access 44 bits so we cant
> 
> That won't help you. You might not be dealing with RAM at the bottom of the
> address space. You might also be in platforms with an iommu, or doing DMA
> to another PCI target
> 
> > Tell me something related to this or any link which i can refer
> 
> Assuming the device is doing bus mastering. Read
> Documentation/DMA-mapping.txt
> 

Maximum Virtual and Physical address in ia64

[Sanket Rathi]

No actually i don't want that for DMA it is for diffrent requirment.
actually in our device there is a page table in device which have
virtual to physical address translation we save virtual address in device
and corresponding physical address. but we can store only upto 44 bit
information of virtual address thats why i want that.

Can you help me in this

Thanks in advance

-----
--------Sanket


> > I just want to know how can we restrict the maximum virtual memory and
> > maximum physical memory on ia64 platform.
> > kernel. Actually we have a device which can only access 44 bits so we cant
> 
> That won't help you. You might not be dealing with RAM at the bottom of the
> address space. You might also be in platforms with an iommu, or doing DMA
> to another PCI target
> 
> > Tell me something related to this or any link which i can refer
> 
> Assuming the device is doing bus mastering. Read
> Documentation/DMA-mapping.txt
> 

Re: your mail

[Alan Cox]

> No actually i don't want that for DMA it is for diffrent requirment.
> actually in our device there is a page table in device which have
> virtual to physical address translation we save virtual address in device
> and corresponding physical address. but we can store only upto 44 bit 
> information of virtual address thats why i want that.

Still read Documentation/DMA-mapping.txt

Whether its DMA or not you are going to need to keep the allocations below
44bits and thats what the DMA allocators do

Re: your mail

[David Mosberger]

>>>>> On Thu, 16 May 2002 21:24:10 +0530 (IST), Sanket Rathi <sanket.rathi@cdac.ernet.in> said:

  Sanket> No actually i don't want that for DMA it is for diffrent
  Sanket> requirment.  actually in our device there is a page table in
  Sanket> device which have virtual to physical address translation we
  Sanket> save virtual address in device and corresponding physical
  Sanket> address. but we can store only upto 44 bit information of
  Sanket> virtual address thats why i want that.

  Sanket> Can you help me in this

There is no way to limit virtual memory to 44 bits.  I don't know how
your device works, but just fyi: ia64 divides the address space into 8
equal-sized regions and user space applications tend to use at least
two regions (2 for text and 3 for data/stack).  This means that even
with the smallest page size, you'll have to take virtual address bits
61-63 into account.

Hope this helps,

	--david
--
Interested in learning more about IA-64 Linux?  Try http://www.lia64.org/book/