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From: Pavel Begunkov <[email protected]>
To: Jens Axboe <[email protected]>, [email protected]
Subject: Re: [PATCH 02/16] io_uring: cqe init hardening
Date: Thu, 24 Aug 2023 17:28:19 +0100	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

On 8/19/23 16:03, Jens Axboe wrote:
> On 8/15/23 11:31 AM, Pavel Begunkov wrote:
>> io_kiocb::cqe stores the completion info which we'll memcpy to
>> userspace, and we rely on callbacks and other later steps to populate
>> it with right values. We have never had problems with that, but it would
>> still be safer to zero it on allocation.
>>
>> Signed-off-by: Pavel Begunkov <[email protected]>
>> ---
>>   io_uring/io_uring.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
>> index e189158ebbdd..4d27655be3a6 100644
>> --- a/io_uring/io_uring.c
>> +++ b/io_uring/io_uring.c
>> @@ -1056,7 +1056,7 @@ static void io_preinit_req(struct io_kiocb *req, struct io_ring_ctx *ctx)
>>   	req->link = NULL;
>>   	req->async_data = NULL;
>>   	/* not necessary, but safer to zero */
>> -	req->cqe.res = 0;
>> +	memset(&req->cqe, 0, sizeof(req->cqe));
>>   }
>>   
>>   static void io_flush_cached_locked_reqs(struct io_ring_ctx *ctx,
> 
> I think this is a good idea, but I wonder if we should open-clear it
> instead. I've had cases in the past where that's more efficient than
> calling memset.

I don't think it ever happens for 16 byte memcpy, and in either
case it's a cache refill, quite a slow path. I believe memcpy is
better here.

-- 
Pavel Begunkov

  reply	other threads:[~2023-08-24 16:32 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-08-15 17:31 [RFC 00/16] caching and SQ/CQ optimisations Pavel Begunkov
2023-08-15 17:31 ` [PATCH 01/16] io_uring: improve cqe !tracing hot path Pavel Begunkov
2023-08-15 17:31 ` [PATCH 02/16] io_uring: cqe init hardening Pavel Begunkov
2023-08-19 15:03   ` Jens Axboe
2023-08-24 16:28     ` Pavel Begunkov [this message]
2023-08-24 16:49       ` Jens Axboe
2023-08-15 17:31 ` [PATCH 03/16] io_uring: simplify big_cqe handling Pavel Begunkov
2023-08-15 17:31 ` [PATCH 04/16] io_uring: refactor __io_get_cqe() Pavel Begunkov
2023-08-15 17:31 ` [PATCH 05/16] io_uring: optimise extra io_get_cqe null check Pavel Begunkov
2023-08-15 17:31 ` [PATCH 06/16] io_uring: reorder cqring_flush and wakeups Pavel Begunkov
2023-08-15 17:31 ` [PATCH 07/16] io_uring: merge iopoll and normal completion paths Pavel Begunkov
2023-08-15 17:31 ` [PATCH 08/16] io_uring: compact SQ/CQ heads/tails Pavel Begunkov
2023-08-19 15:05   ` Jens Axboe
2023-08-24 16:29     ` Pavel Begunkov
2023-08-15 17:31 ` [PATCH 09/16] io_uring: add option to remove SQ indirection Pavel Begunkov
2023-08-19 15:06   ` Jens Axboe
2023-08-15 17:31 ` [PATCH 10/16] io_uring: static_key for !IORING_SETUP_NO_SQARRAY Pavel Begunkov
2023-08-15 17:31 ` [PATCH 11/16] io_uring: move non aligned field to the end Pavel Begunkov
2023-08-15 17:31 ` [PATCH 12/16] io_uring: banish non-hot data to end of io_ring_ctx Pavel Begunkov
2023-08-15 17:31 ` [PATCH 13/16] io_uring: separate task_work/waiting cache line Pavel Begunkov
2023-08-15 17:31 ` [PATCH 14/16] io_uring: move multishot cqe cache in ctx Pavel Begunkov
2023-08-15 17:31 ` [PATCH 15/16] io_uring: move iopoll ctx fields around Pavel Begunkov
2023-08-15 17:31 ` [PATCH 16/16] io_uring: force inline io_fill_cqe_req Pavel Begunkov

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