Re: [PATCH for-rc 4/6] RDMA/efa: Use API to get contiguous memory blocks aligned to device supported page size

[Gal Pressman <galpress@xxxxxxxxxx>]

On 29/05/2019 20:20, Saleem, Shiraz wrote:
>> Subject: Re: [PATCH for-rc 4/6] RDMA/efa: Use API to get contiguous memory
>> blocks aligned to device supported page size
>>
>> On Tue, May 28, 2019 at 03:46:16PM +0300, Gal Pressman wrote:
>>> @@ -1500,13 +1443,17 @@ struct ib_mr *efa_reg_mr(struct ib_pd *ibpd, u64
>> start, u64 length,
>>>  	params.iova = virt_addr;
>>>  	params.mr_length_in_bytes = length;
>>>  	params.permissions = access_flags & 0x1;
>>> -	max_page_shift = fls64(dev->dev_attr.page_size_cap);
>>>
>>> -	efa_cont_pages(mr->umem, start, max_page_shift, &npages,
>>> -		       &params.page_shift, &params.page_num);
>>> +	pg_sz = ib_umem_find_best_pgsz(mr->umem,
>>> +				       dev->dev_attr.page_size_cap,
>>> +				       virt_addr);
>>
>> I think this needs to check pg_sz is not zero..
>>
> 
> What is the smallest page size this driver supports?

The page size capability is queried from the device, the smallest page size is
currently 4k.

Isn't PAGE_SIZE always supported? What did drivers do before
ib_umem_find_best_pgsz() existed in case they didn't support PAGE_SIZE?

I doubt there is/will be a real use-case where it matters for EFA, but I can add
the check to be on the safe side.