Re: [Xen-devel] kmap_atomic issue with SLES11SP1 32bit XEN driver code

[dbrace <dab@xxxxxx>]

Yes

On 12/07/2011 03:52 PM, scameron@xxxxxxxxxxxxxxxxxx wrote:
> On Wed, Dec 07, 2011 at 03:47:57PM -0600, dbrace wrote:
> > kernel: Linux 360 2.6.32.12-0.7-xen #1 SMP 2010-05-20 11:14:20 +0200
> > i686 i686 i386 GNU/Linux
> >
> > I am having issues with some code that uses kmap_atomic(). I am getting:
> >
> > BUG: unable to handle kernel paging request at 23a1a000 (which is the
> > address returned from kmap_atomic().)
> >
> > The same code works when running on non-XEN 32bit kernels so I am
> > wondering why this does not work under
> > XEN kernels. Is there a different approach that I need to take for 32bit
> > XEN kernels?
> >
> > I really only need to do this code segment if the memory address is a
> > high memory address. Is there a MACRO or function
> > that can help me determine this?
> >
> > Here is a code snippet:
> >
> >                  void *linux_vaddr = NULL;       /* kmapped temporary
> > virtual address */
> >                  int linux_page_offset = 0;      /* offset in page */
> >                  int count = 0;                  /* bytes left to
> > transfer */
> >                  int left = byte_count;          /* number of bytes left
> > to transfer */
> >                  int memcpysize = 0;             /* current size to
> > transfer */
> >                  struct page *linux_page = NULL; /* calculated page */
> >                  int kmap_flags = 0;
> >
> >                  linux_page = __pfn_to_page(physical_address>>  PAGE_SHIFT);
> >                  linux_page_offset = (physical_address&
> > 0x0000000000000FFFULL);
> >                  memcpysize =  min((PAGE_SIZE - linux_page_offset), left);
> >
> >                  kmap_flags = KM_USER0;
> >
> >                  linux_vaddr = kmap_atomic(linux_page, kmap_flags) +
> > linux_page_offset;
> >
> >                  printk("%s: called kmap_atomic, "
> >                          "calling memcpy linux_vaddr = 0x%x virt_address
> > = 0x%x count = 0x%x\n",
> >                          __func__, linux_vaddr, virt_address, count);
> >                  /*
> >                   * Either need to copy to a kmapped destination
> >                   * or a kmapped source.
> >                   */
> >                  if (type == 0) // Write to s/g element, dest virtual
> > addr was known.
> >                          memcpy((void *)virt_address+count, (void
> > *)linux_vaddr, memcpysize);
> >                  else // Source virt. address was known.
> >                          memcpy((void *)linux_vaddr, (void
> > *)virt_address+count, memcpysize);
> Just to be clear, it's these memcpy's that get the BUG, correct?
>
> -- steve
>
>
> >                  printk("OS_Linux32_Xfer_SG_Page: calling kunmap_atomic, "
> >                          "calling memcpy linux_vaddr = 0x%lx\n",
> > linux_vaddr);
> >
> >                  kunmap_atomic(linux_vaddr, kmap_flags);
> >
> >
> > --
> > Don Brace
> > SPSN Linux Development
> > Hewlett-Packard Company
--
Don Brace
SPSN Linux Development
Hewlett-Packard Company

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-devel