Messages in this thread | | | Date | Mon, 6 May 2002 03:20:54 +0200 | From | Andrea Arcangeli <> | Subject | Re: Bug: Discontigmem virt_to_page() [Alpha,ARM,Mips64?] |
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On Mon, May 06, 2002 at 03:07:07AM +0200, Daniel Phillips wrote: > On Monday 06 May 2002 02:55, Russell King wrote: > > On Mon, May 06, 2002 at 01:54:52AM +0200, Daniel Phillips wrote: > > > I must be guilty of not explaining clearly. Suppose you have the following > > > physical memory map: > > > > > > 0: 128 MB > > > 8000,0000: 128 MB > > > 1,0000,0000: 128 MB > > > 1,8000,0000: 128 MB > > > 2,0000,0000: 128 MB > > > 2,8000,0000: 128 MB > > > 3,0000,0000: 128 MB > > > 3,8000,0000: 128 MB > > > > > > The total is 1 GB of installed ram. Yet the kernel's 1G virtual space, > > > can only handle 128 MB of it. > > > > I see no problem with the above with the existing discontigmem stuff. > > discontigmem does *not* require a linear relationship between kernel > > virtual and physical memory. I've been running kernels for a while > > on such systems. > > Look, you've got this: > > #define __phys_to_virt(ppage) ((unsigned long)(ppage) + PAGE_OFFSET - PHYS_OFFSET) > > So, since __phys_to_virt (and hence phys_to_virt and __va) is clearly linear, the > relation __pa(__va(kva)) == kva cannot hold. Perhaps that doesn't bother you?
Check my previous email:
[..] They will all be normal zones provided you implement a static view of them in the kernel virtual address space, and you also cover page_address/virt_to_page [..]
Depending on the kind of coalescing of those chunks in the direct mapping virt_to_page/page_address will vary. virt_to_page and page_address will have all the necessary internal knowledge in order to make it all zone_normal.
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