netdev - Re: [PATCH net-next 1/5] ch_ktls: Use kmap_local_page() instead of kmap

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Message-ID: <4bcad8cf-2525-bd7c-9d58-ae43a7720191@intel.com>
Date:   Fri, 18 Nov 2022 10:27:56 -0800
From:   Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
To:     "Fabio M. De Francesco" <fmdefrancesco@...il.com>,
        <netdev@...r.kernel.org>
CC:     Ira Weiny <ira.weiny@...el.com>,
        Ayush Sawal <ayush.sawal@...lsio.com>,
        Vinay Kumar Yadav <vinay.yadav@...lsio.com>,
        Rohit Maheshwari <rohitm@...lsio.com>
Subject: Re: [PATCH net-next 1/5] ch_ktls: Use kmap_local_page() instead of
 kmap_atomic()

On 11/18/2022 12:14 AM, Fabio M. De Francesco wrote:
> On giovedì 17 novembre 2022 23:25:53 CET Anirudh Venkataramanan wrote:
>> kmap_atomic() is being deprecated in favor of kmap_local_page().
>> Replace kmap_atomic() and kunmap_atomic() with kmap_local_page()
>> and kunmap_local() respectively.
>>
>> Note that kmap_atomic() disables preemption and page-fault processing,
>> but kmap_local_page() doesn't. Converting the former to the latter is safe
>> only if there isn't an implicit dependency on preemption and page-fault
>> handling being disabled, which does appear to be the case here.
>>
>> Also note that the page being mapped is not allocated by the driver,
>> and so the driver doesn't know if the page is in normal memory. This is the
>> reason kmap_local_page() is used as opposed to page_address().
>>
>> I don't have hardware, so this change has only been compile tested.
>>
>> Cc: Ayush Sawal <ayush.sawal@...lsio.com>
>> Cc: Vinay Kumar Yadav <vinay.yadav@...lsio.com>
>> Cc: Rohit Maheshwari <rohitm@...lsio.com>
>> Cc: Ira Weiny <ira.weiny@...el.com>
>> Cc: Fabio M. De Francesco <fmdefrancesco@...il.com>
>> Signed-off-by: Anirudh Venkataramanan <anirudh.venkataramanan@...el.com>
>> ---
>>   .../ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c | 10 +++++-----
>>   1 file changed, 5 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
>> b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c index
>> da9973b..d95f230 100644
>> --- a/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
>> +++ b/drivers/net/ethernet/chelsio/inline_crypto/ch_ktls/chcr_ktls.c
>> @@ -1853,24 +1853,24 @@ static int chcr_short_record_handler(struct
>> chcr_ktls_info *tx_info, i++;
>>   			}
>>   			f = &record->frags[i];
>> -			vaddr = kmap_atomic(skb_frag_page(f));
>> +			vaddr = kmap_local_page(skb_frag_page(f));
>>
>>   			data = vaddr + skb_frag_off(f)  + remaining;
>>   			frag_delta = skb_frag_size(f) - remaining;
>>
>>   			if (frag_delta >= prior_data_len) {
>>   				memcpy(prior_data, data,
> prior_data_len);
>> -				kunmap_atomic(vaddr);
>> +				kunmap_local(vaddr);
>>   			} else {
>>   				memcpy(prior_data, data, frag_delta);
>> -				kunmap_atomic(vaddr);
>> +				kunmap_local(vaddr);
>>   				/* get the next page */
>>   				f = &record->frags[i + 1];
>> -				vaddr = kmap_atomic(skb_frag_page(f));
>> +				vaddr =
> kmap_local_page(skb_frag_page(f));
>>   				data = vaddr + skb_frag_off(f);
>>   				memcpy(prior_data + frag_delta,
>>   				       data, (prior_data_len -
> frag_delta));
>> -				kunmap_atomic(vaddr);
>> +				kunmap_local(vaddr);
>>   			}
>>   			/* reset tcp_seq as per the prior_data_required
> len */
>>   			tcp_seq -= prior_data_len;
>> --
>> 2.37.2
> 
> The last conversion could have been done with memcpy_from_page(). However,
> it's not that a big deal. Therefore...
> 
> Reviewed-by: Fabio M. De Francesco <fmdefrancesco@...il.com>

Yeah, using memcpy_from_page() is cleaner. I'll update this patch, and 
probably 4/5 too.

Thanks!
Ani