Re: [PATCH v5 04/12] iommu/vt-d: Add 256-bit invalidation descriptor support

[Lu Baolu <baolu.lu@linux.intel.com>]

Hi Joerg,

On 12/5/18 11:56 PM, Joerg Roedel wrote:
> On Tue, Dec 04, 2018 at 02:13:31PM +0800, Lu Baolu wrote:
>> The existing code uses GFP_ATOMIC, this patch only changes the size of
>> the allocated desc_page.
>>
>> I don't think we really need GFP_ATOMIC here (and also for some other
>> places). I will clean up them in a separated patch.
> 
> Okay, thanks.
> 
>>> In this patch, there is some code like the code below. It calculates
>>> destination address of memcpy with qi->desc. If it's still struct qi_desc
>>> pointer, the calculation result would be wrong.
>>>
>>> +			memcpy(desc, qi->desc + (wait_index << shift),
>>> +			       1 << shift);
>>>
>>> The change of the calculation method is to support 128 bits invalidation
>>> descriptors and 256 invalidation descriptors in this unified code logic.
>>>
>>> Also, the conversation between Baolu and me may help.
>>>
>>> https://lore.kernel.org/patchwork/patch/1006756/
>>
>> Yes. We need to support different descriptor size.
> 
> Okay, pointer arithmetic on void* isn't well defined in the C standard,
> afaik. But it should work with GCC, so it's probably fine.
> 
> Unrelated to this patch-set, the whole qi management code needs some
> cleanups, it queues a sync after every command and has very tricky
> locking. This patch-set further complicates matters there, so it is
> probably time for a clean re-write of that part?

Sure. I will start the cleanups(including the unnecessary ATOMIC page
allocation) and submit them in a separated patch set after well tested.

Best regards,
Lu Baolu