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

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

See include/asm-xen/asm-i386/agp.h

/* GATT allocation. Returns/accepts GATT kernel virtual address. */
#define alloc_gatt_pages(order) ({
\
        char *_t; dma_addr_t _d;
\
        _t = dma_alloc_coherent(NULL,PAGE_SIZE<<(order),&_d,GFP_KERNEL);
\
        _t; })
#define free_gatt_pages(table, order)   \
 
dma_free_coherent(NULL,PAGE_SIZE<<(order),(table),virt_to_bus(table)) 

There may be other changes in the file too.

Ian

> -----Original Message-----
> From: Langsdorf, Mark [mailto:mark.langsdorf@xxxxxxx] 
> Sent: 30 September 2005 23:12
> To: Ian Pratt; xen-devel@xxxxxxxxxxxxxxxxxxx
> Subject: RE: [Xen-devel] IOMMU support: 
> __direct_remap_pfn_range() fails
> 
> > 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.
> > > 
> > > 
> > 
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
> > 
> > 
> 
> 

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