From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Thomas Monjalon <thomas@monjalon.net>,
Cheng Jiang <Cheng1.jiang@intel.com>,
bruce.richardson@intel.com
Cc: chenbo.xia@intel.com, dev@dpdk.org, jiayu.hu@intel.com,
yvonnex.yang@intel.com, yinan.wang@intel.com, alexr@nvidia.com,
shahafs@nvidia.com
Subject: Re: [dpdk-dev] [PATCH] examples/vhost: fix ioat ring space in callbacks
Date: Wed, 7 Apr 2021 10:48:13 +0200 [thread overview]
Message-ID: <2cbf905c-bbc2-6959-6606-e1a84cddc0ac@redhat.com> (raw)
In-Reply-To: <2267082.chWHW8dCnR@thomas>
On 4/7/21 10:26 AM, Thomas Monjalon wrote:
> 07/04/2021 09:47, Maxime Coquelin:
>>
>> On 3/17/21 6:40 AM, Cheng Jiang wrote:
>>> We use ioat ring space for determining if ioat callbacks can enqueue a
>>> packet to ioat device. But there is one slot can't be used in ioat
>>> ring due to the ioat driver design, so we need to reduce one slot in
>>> ioat ring to prevent ring size mismatch in ioat callbacks.
>>>
>>> Fixes: 2aa47e94bfb2 ("examples/vhost: add ioat ring space count and check")
>>> Cc: stable@dpdk.org
>>>
>>> Signed-off-by: Cheng Jiang <Cheng1.jiang@intel.com>
>>> ---
>>> examples/vhost/ioat.c | 2 +-
>>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/examples/vhost/ioat.c b/examples/vhost/ioat.c
>>> index 60b73be93..9cb5e0d50 100644
>>> --- a/examples/vhost/ioat.c
>>> +++ b/examples/vhost/ioat.c
>>> @@ -113,7 +113,7 @@ open_ioat(const char *value)
>>> goto out;
>>> }
>>> rte_rawdev_start(dev_id);
>>> - cb_tracker[dev_id].ioat_space = IOAT_RING_SIZE;
>>> + cb_tracker[dev_id].ioat_space = IOAT_RING_SIZE - 1;
>>
>> That really comforts me in thinking we need a generic abstraction for
>> DMA devices. How is the application developer supposed to know that
>> the DMA driver has such weird limitations?
>
> Having a generic DMA API may be interesting.
> Do you know any other HW candidate for such an API?
> Do you think rte_memcpy can be used as a SW driver?
Yes, I guess we could create a vdev driver with MEM_TO_MEM capability
using rte_memcpy().
Note that IOAT in the Kernel is supported by the DMA framework.
Regards,
Maxime
next prev parent reply other threads:[~2021-04-07 8:48 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-17 5:40 Cheng Jiang
2021-03-17 6:58 ` Hu, Jiayu
2021-04-07 7:47 ` Maxime Coquelin
2021-04-07 7:54 ` Hu, Jiayu
2021-04-13 8:50 ` Maxime Coquelin
2021-04-13 9:55 ` Jiang, Cheng1
2021-04-07 8:26 ` Thomas Monjalon
2021-04-07 8:43 ` Thomas Monjalon
2021-04-18 15:10 ` Liang Ma
2021-04-07 8:48 ` Maxime Coquelin [this message]
2021-04-28 2:09 ` Xia, Chenbo
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