Re: [PATCH v11 08/10] iommu/vt-d: assign new page table for dma_map

[Li, ZhenHua]

Hi Baoquan,
During driver being loaded and initialized, when there is a new dma
request, the function
               __get_valid_domain_for_dev
is called, and then new page is mapped.

Please check this:
struct dma_map_ops intel_dma_ops = {
        .alloc = intel_alloc_coherent,
        .free = intel_free_coherent,
        .map_sg = intel_map_sg,
        .unmap_sg = intel_unmap_sg,
        .map_page = intel_map_page,
        .unmap_page = intel_unmap_page,
        .mapping_error = intel_mapping_error,
};

You can also add dump_stack() in __get_valid_domain_for_dev to debug.

Thanks
Zhenhua

On 05/21/2015 02:54 PM, Baoquan He wrote:
> On 05/21/15 at 09:27am, Li, ZhenHua wrote:
> > Hi Baoquan,
> >
> > In the early version of this patchset, old page tables are used by new
> > kernel.  But as discussed, we need to make kernel use new pages when
> > there is a new dma request , so we need to unmap the pages which were
> > mapped in old kernel, and this is what this patch does.
>
> OK, just a new page table allocated in init_domain(), right? I thought a
> specific empty page-table is allocated for these new domains in kdump
> kernel.
>
> > Thanks
> > Zhenhua
> >
> > On 05/21/2015 07:52 AM, Baoquan He wrote:
> > > On 05/11/15 at 05:52pm, Li, Zhen-Hua wrote:
> > > > When a device driver issues the first dma_map command for a device, we
> > > > assign a new and empty page-table, thus removing all mappings from the
> > > > old kernel for the device.
> > >
> > > Hi Zhenhua,
> > >
> > >  From your patch I got it will remove all mappings, assign a new
> > > page-table. But I didn't got why you stress an empty page-table. Did I
> > > miss anything?
> > >
> > > Thanks
> > > Baoquan
> > >
> > > > Signed-off-by: Li, Zhen-Hua <zhen-hual@xxxxxx>
> > > > --
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