RE: [Xen-devel] IOMMU support: __direct_remap_pfn_range() fails

["Langsdorf, Mark" <mark.langsdorf@xxxxxxx>]

> What's calling direct_remap_page_range?

call stack is
        __direct_remap_page_range
        __ioremap
        ioremap_nocache
        agp_generic_create_gatt_table
        agp_backend_initialization
        etc, etc.

the memory that is being remapped is allocated in
drivers/char/agp/generic.c:agp_generic_create_gatt_table()
by a call to alloc_gatt_pages() (which is just a #define of
__get_free_pages on x86_64).
 
> My suspicion is that the driver is allocating some memory and 
> then calling ioremap on it, which isn't a good thing to do as 
> its not MMIO memory. You can get away with this on native, 
> but not Xen.
> 
> Can you point us at the appropriate section of the driver code.

See above.  How do I fix this?

Thanks for the help.

-Mark Langsdorf
AMD, Inc.

> > > > I am working on getting IOMMU support for AMD64.
> > > > ...the agpgart code is still failing.
> > > > 
> > > > I have tracked the problem down to line 92 of ioremap.c, in
> > > > __direct_remap_pfn_range().
> > > > The failing instruction is a call to HYPERVISOR_mmu_update().
> > > 
> > > What are the arguments to direct_remap_pfn_range?
> > 
> > struct struct_mm *mm = 0x804c9540
> > unsigned long address = 80000
> > unsigned long mfn = 4280
> > unsigned long size = 80000
> > pgprot_t prot = 77
> > domid_t domid = 7ff1
> > 
> > The arguments the HYPERVISOR call are
> >     u = 43418
> >     v - u = 800
> >     domid = 7ff1
> > 
> > > With a verbose=y build of Xen what debug output do you 
> get from xen
> > > (on the serial line).
> > 
> > (XEN) (file=/usr/src/xen-unstable/xen-source/xen/include/asm/mm.h,
> > line=202)
> > Error pfn 4280: rd=ffff8300001c7080, od=0000000000000000,
> > caf=00000000,
> > taf=0000000000000006
> > 
> > If I'm reading asm/mm.h:get_page() right, it's failing
> > because the page->count_info is 0, but I don't know who set 
> > that value or if that's meaningful.
> > 
> > -Mark Langsdorf
> > AMD, Inc.
> > 
> > 
> 
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> 
> 


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