Re: pte_page

From: mdaljeet@in.ibm.com
Date: Thu May 31 2001 - 04:57:38 EST


I am doing a DMA from a card to system memory. The system memory "physical
address" is '0x104000'. I am doing this on x86 with kernel version 2.4.2.
Can this address be the address of a user space buffer?

Regards,
Daljeet.

|--------+----------------------->
| | Ingo Molnar |
| | <mingo@elte.h|
| | u> |
| | |
| | 05/30/01 |
| | 11:09 PM |
| | Please |
| | respond to |
| | mingo |
| | |
|--------+----------------------->
>--------------------------------------------------------|
  | |
  | To: Pete Wyckoff <pw@osc.edu> |
  | cc: Daljeet Maini/India/IBM@IBMIN, |
  | linux-kernel@vger.kernel.org |
  | Subject: Re: pte_page |
>--------------------------------------------------------|

On Wed, 30 May 2001, Pete Wyckoff wrote:

> > __pa(page_address(pte_page(pte))) is the address you want. [or
> > pte_val(*pte) & (PAGE_SIZE-1) on x86 but this is platform-dependent.]
>
> Does this work on x86 non-kmapped highmem user pages too? (i.e. is
> page->virtual valid for every potential user page.)

you are right, the highmem-compatible solution is to use page-mem_map as
the physical page index.

     Ingo

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