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 at hp.com>
>>>> --
