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 <venkatesh.pallipadi@xxxxxxxxx>
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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