[uml-devel] Re: prot |= _PAGE_PCD | _PAGE_PWT;

[uml-devel] Re: prot |= _PAGE_PCD | _PAGE_PWT;

[Jeff Dike]

On Fri, Jul 15, 2005 at 03:26:54PM -0400, Majid Salame wrote:
>  in asm-um/pgtable.h we do not have definitions and may be for good
> reason for PAGE_PCD and _PAGE_PWT.
> 
> #define _PAGE_PWT	0x008
> #define _PAGE_PCD	0x010
> 
> Can I in UML recode this statement in much same way drivers/char/mem.c
>      prot |= _PAGE_PCD | _PAGE_PWT;

What do they mean?

			Jeff


-------------------------------------------------------
SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
from IBM. Find simple to follow Roadmaps, straightforward articles,
informative Webcasts and more! Get everything you need to get up to
speed, fast. http://ads.osdn.com/?ad_id=7477&alloc_id=16492&op=click
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel

Re: [uml-devel] prot |= _PAGE_PCD | _PAGE_PWT;

[Blaisorblade]

On Friday 15 July 2005 21:26, Majid Salame wrote:
>  in asm-um/pgtable.h we do not have definitions and may be for good
> reason for PAGE_PCD and _PAGE_PWT.

From what I see, they're about uncacheability of memory, which isn't probably 
supportable at all in UML (we might go to using madvise but I don't think 
it's worth).

And as done in drivers/char/mem.c, there an access macro to use it, i.e. 
pgprot_noncached, to use only if defined (I guess on arch missing it it 
should be defined as a no-op).

> #define _PAGE_PWT	0x008
> #define _PAGE_PCD	0x010

> Can I in UML recode this statement in much same way drivers/char/mem.c
>      prot |= _PAGE_PCD | _PAGE_PWT;

So, what's the question? The answer is obviously yes. Note that I'm referring 
to this version of the sources (taken from latest git snapshot):

static int mmap_mem(struct file * file, struct vm_area_struct * vma)
{
#if defined(__HAVE_PHYS_MEM_ACCESS_PROT)
        unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;

        vma->vm_page_prot = phys_mem_access_prot(file, offset,
                                                 vma->vm_end - vma->vm_start,
                                                 vma->vm_page_prot);
#elif defined(pgprot_noncached)
        unsigned long offset = vma->vm_pgoff << PAGE_SHIFT;
        int uncached;

        uncached = uncached_access(file, offset);
        if (uncached)
                vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
#endif

-- 
Inform me of my mistakes, so I can keep imitating Homer Simpson's "Doh!".
Paolo Giarrusso, aka Blaisorblade (Skype ID "PaoloGiarrusso", ICQ 215621894)
http://www.user-mode-linux.org/~blaisorblade

	

	
		
___________________________________ 
Yahoo! Mail: gratis 1GB per i messaggi e allegati da 10MB 
http://mail.yahoo.it



-------------------------------------------------------
SF.Net email is sponsored by: Discover Easy Linux Migration Strategies
from IBM. Find simple to follow Roadmaps, straightforward articles,
informative Webcasts and more! Get everything you need to get up to
speed, fast. http://ads.osdn.com/?ad_idt77&alloc_id\x16492&opÌk
_______________________________________________
User-mode-linux-devel mailing list
User-mode-linux-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel