remap_pfn_range() and mapping RAM

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Hello everyone,

While developing a method for mapping RAM memory into user space
I stumbled across Suresh Siddha's commit that "broke" my code:

commit be03d9e8022030c16abf534e33e185bfc3d40eef
x86, pat: fix warn_on_once() while mapping 0-1MB range with /dev/mem

I believe there were important reasons for the changes but how do I map
user RAM memory into user space? Up to this point I've used something
along the lines of (error checking removed):

#v+
static int file_mmap(struct file *file, struct vm_area_struct *vma)
{
const size_t start =3D /* physical address of memory allocated
using alloc_bootmem_low_pages() */;

return remap_pfn_range(vma, vma->vm_start,
(start >> PAGE_SHIFT) + vma->vm_pgoff
vma->vm_end - vma->vm_start,
vma->vm_page_prot);
}
#v-

Reverting the be03... commit makes it work again but I guess it's not
a good way to solve this problem.

Could anyone point me to proper function which may be used like
remap_pfn_range() but work on RAM addresses? It is important, that the
function will work in similar fashion, ie. create raw PFN mappings
without associated struct page.

=2D-=20
Best regards, _ _
.o. | Liege of Serenly Enlightened Majesty of o' \,=3D./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
ooo +------ooO--(_)--Ooo--

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Re: remap_pfn_range() and mapping RAM

On Sun, 2009-05-10 at 09:46 -0700, Michal Nazarewicz wrote:
> Hello everyone,
>
> While developing a method for mapping RAM memory into user space
> I stumbled across Suresh Siddha's commit that "broke" my code:
>
> commit be03d9e8022030c16abf534e33e185bfc3d40eef
> x86, pat: fix warn_on_once() while mapping 0-1MB range with /dev/mem
>
> I believe there were important reasons for the changes but how do I map
> user RAM memory into user space? Up to this point I've used something
> along the lines of (error checking removed):
>
> #v+
> static int file_mmap(struct file *file, struct vm_area_struct *vma)
> {
> const size_t start = /* physical address of memory allocated
> using alloc_bootmem_low_pages() */;
>
> return remap_pfn_range(vma, vma->vm_start,
> (start >> PAGE_SHIFT) + vma->vm_pgoff
> vma->vm_end - vma->vm_start,
> vma->vm_page_prot);
> }
> #v-
>
> Reverting the be03... commit makes it work again but I guess it's not
> a good way to solve this problem.
>
> Could anyone point me to proper function which may be used like
> remap_pfn_range() but work on RAM addresses? It is important, that the
> function will work in similar fashion, ie. create raw PFN mappings
> without associated struct page.

Are you using 2.6.29?

This mainline commit:

commit 4bb9c5c02153dfc89a6c73a6f32091413805ad7d
Author: Pallipadi, Venkatesh
Date: Thu Mar 12 17:45:27 2009 -0700

has fixed this issue with this portion of the patch:

diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
index e0ab173..21bc1f7 100644
--- a/arch/x86/mm/pat.c
+++ b/arch/x86/mm/pat.c
@@ -641,10 +641,11 @@ static int reserve_pfn_range(u64 paddr, unsigned
long size
is_ram = pat_pagerange_is_ram(paddr, paddr + size);

/*
- * reserve_pfn_range() doesn't support RAM pages.
+ * reserve_pfn_range() doesn't support RAM pages. Maintain the
current
+ * behavior with RAM pages by returning success.
*/
if (is_ram != 0)
- return -EINVAL;
+ return 0;

ret = reserve_memtype(paddr, paddr + size, want_flags, &flags);
if (ret)

thanks
suresh

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Re: remap_pfn_range() and mapping RAM

> On Sun, 2009-05-10 at 09:46 -0700, Michal Nazarewicz wrote:
>> While developing a method for mapping RAM memory into user space
>> I stumbled across Suresh Siddha's commit that "broke" my code:
>>
>> commit be03d9e8022030c16abf534e33e185bfc3d40eef
>> x86, pat: fix warn_on_once() while mapping 0-1MB range with /dev/mem
>>
>> I've used something along the lines of (error checking removed):
>>
>> #v+
>> return remap_pfn_range(vma, vma->vm_start,
>> (start >> PAGE_SHIFT) + vma->vm_pgoff
>> vma->vm_end - vma->vm_start,
>> vma->vm_page_prot);
>> #v-
>>
>> Reverting the be03... commit makes it work again but I guess it's not
>> a good way to solve this problem.

Suresh Siddha writes:
> This mainline commit:
>
> commit 4bb9c5c02153dfc89a6c73a6f32091413805ad7d
> Author: Pallipadi, Venkatesh
> Date: Thu Mar 12 17:45:27 2009 -0700
>
> has fixed this issue with this portion of the patch:

Ah, thanks, it works great now! And sorry for the bother (I should've
checked with 2.6.29.2 at least).

--
Best regards, _ _
.o. | Liege of Serenly Enlightened Majesty of o' \,=./ `o
..o | Computer Science, Michal "mina86" Nazarewicz (o o)
ooo +------ooO--(_)--Ooo--
--
To unsubscribe from this list: send the line "unsubscribe linux-newbie" in
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More majordomo info at http://vger.kernel.org/majordomo-info.html
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