From: Maxime Coquelin <maxime.coquelin@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH 2/6] vhost: get guest/host physical address mappings
Date: Tue, 23 Aug 2016 16:05:48 +0200 [thread overview]
Message-ID: <b9ff6270-d082-d7d0-1a60-f31c6634dcea@redhat.com> (raw)
In-Reply-To: <20160823134924.GN30752@yliu-dev.sh.intel.com>
On 08/23/2016 03:49 PM, Yuanhan Liu wrote:
> On Tue, Aug 23, 2016 at 03:25:33PM +0200, Maxime Coquelin wrote:
>>
>>
>> On 08/23/2016 02:32 PM, Yuanhan Liu wrote:
>>>>> +
>>>>>>> + /* FIXME */
>>>>>>> + RTE_LOG(INFO, VHOST_CONFIG, ":: %u ::\n", pre_read);
>>>>> For my information, what is the purpose of pre_read?
>>> Again, I put a FIXME here, but I forgot to add some explanation.
>>>
>>> Here is the thing: the read will make sure the kernel populate the
>>> corresponding PTE entry, so that rte_mem_virt2phy() will return proper
>>> physical address, otherwise, invalid value is returned.
>>>
>>> I can't simply do the read but do not actually reference/consume it.
>>> Otherwise, the compiler will treat it as some noops and remove it.
>>>
>>> An ugly RTE_LOG will make sure the read operation is not eliminated.
>>> I'm seeking a more proper way to achieve that. Maybe I can add a new
>>> field in virtio_net structure and store it there.
>>>
>>> Or, do you have better ideas?
>>
>> This behavior is pretty twisted, no?
>
> I have to say, yes, kind of.
>
>> Shouldn't be rte_mem_virt2phy() role to ensure returning a valid value?
>
> Not exactly. I think rte_mem_virt2phy() is more likely to fetch the
> physical address of huge pages. And for those huge pages, EAL makes
> sure they will be populated: it used to do a zero memset before to
> achieve that. Since 5ce3ace1de45 ("eal: remove unnecessary hugepage
> zero-filling"), it uses MAP_POPULATE option instead.
>
> So, thank you that you just remind me of the MAP_POPULATE option.
> I just had a quick try, it worked like a charm :)
Excellent! :)
next prev parent reply other threads:[~2016-08-23 14:05 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-23 8:10 [dpdk-dev] [PATCH 0/6] vhost: add Tx zero copy support Yuanhan Liu
2016-08-23 8:10 ` [dpdk-dev] [PATCH 1/6] vhost: simplify memory regions handling Yuanhan Liu
2016-08-23 9:17 ` Maxime Coquelin
2016-08-24 7:26 ` Xu, Qian Q
2016-08-24 7:40 ` Yuanhan Liu
2016-08-24 7:36 ` Xu, Qian Q
2016-08-23 8:10 ` [dpdk-dev] [PATCH 2/6] vhost: get guest/host physical address mappings Yuanhan Liu
2016-08-23 9:58 ` Maxime Coquelin
2016-08-23 12:32 ` Yuanhan Liu
2016-08-23 13:25 ` Maxime Coquelin
2016-08-23 13:49 ` Yuanhan Liu
2016-08-23 14:05 ` Maxime Coquelin [this message]
2016-08-23 8:10 ` [dpdk-dev] [PATCH 3/6] vhost: introduce last avail idx for Tx Yuanhan Liu
2016-08-23 12:27 ` Maxime Coquelin
2016-08-23 8:10 ` [dpdk-dev] [PATCH 4/6] vhost: add Tx zero copy Yuanhan Liu
2016-08-23 14:04 ` Maxime Coquelin
2016-08-23 14:31 ` Yuanhan Liu
2016-08-23 15:40 ` Maxime Coquelin
2016-08-23 8:10 ` [dpdk-dev] [PATCH 5/6] vhost: add a flag to enable " Yuanhan Liu
2016-09-06 9:00 ` Xu, Qian Q
2016-09-06 9:42 ` Xu, Qian Q
2016-09-06 10:02 ` Yuanhan Liu
2016-09-07 2:43 ` Xu, Qian Q
2016-09-06 9:55 ` Yuanhan Liu
2016-09-07 16:00 ` Thomas Monjalon
2016-09-08 7:21 ` Yuanhan Liu
2016-09-08 7:57 ` Thomas Monjalon
2016-08-23 8:10 ` [dpdk-dev] [PATCH 6/6] examples/vhost: add an option " Yuanhan Liu
2016-08-23 9:31 ` Thomas Monjalon
2016-08-23 12:33 ` Yuanhan Liu
2016-08-23 14:14 ` Maxime Coquelin
2016-08-23 14:45 ` Yuanhan Liu
2016-08-23 14:18 ` [dpdk-dev] [PATCH 0/6] vhost: add Tx zero copy support Maxime Coquelin
2016-08-23 14:42 ` Yuanhan Liu
2016-08-23 14:53 ` Yuanhan Liu
2016-08-23 16:41 ` Maxime Coquelin
2016-08-29 8:32 ` Xu, Qian Q
2016-08-29 8:57 ` Xu, Qian Q
2016-09-23 4:11 ` Yuanhan Liu
2016-10-09 15:20 ` Yuanhan Liu
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 0/7] vhost: add dequeue " Yuanhan Liu
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 1/7] vhost: simplify memory regions handling Yuanhan Liu
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 2/7] vhost: get guest/host physical address mappings Yuanhan Liu
2016-09-26 20:17 ` Maxime Coquelin
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 3/7] vhost: introduce last avail idx for dequeue Yuanhan Liu
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 4/7] vhost: add dequeue zero copy Yuanhan Liu
2016-09-26 20:45 ` Maxime Coquelin
2016-10-06 14:37 ` Xu, Qian Q
2016-10-09 2:03 ` Yuanhan Liu
2016-10-10 10:12 ` Xu, Qian Q
2016-10-10 10:14 ` Maxime Coquelin
2016-10-10 10:22 ` Xu, Qian Q
2016-10-10 10:40 ` Xu, Qian Q
2016-10-10 11:48 ` Maxime Coquelin
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 5/7] vhost: add a flag to enable " Yuanhan Liu
2016-09-26 20:57 ` Maxime Coquelin
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 6/7] examples/vhost: add an option " Yuanhan Liu
2016-09-26 21:05 ` Maxime Coquelin
2016-09-23 4:13 ` [dpdk-dev] [PATCH v2 7/7] net/vhost: " Yuanhan Liu
2016-09-26 21:05 ` Maxime Coquelin
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 0/7] vhost: add dequeue zero copy support Yuanhan Liu
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 1/7] vhost: simplify memory regions handling Yuanhan Liu
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 2/7] vhost: get guest/host physical address mappings Yuanhan Liu
2016-11-29 3:10 ` linhaifeng
2016-11-29 13:14 ` linhaifeng
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 3/7] vhost: introduce last avail idx for dequeue Yuanhan Liu
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 4/7] vhost: add dequeue zero copy Yuanhan Liu
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 5/7] vhost: add a flag to enable " Yuanhan Liu
2016-10-09 7:27 ` [dpdk-dev] [PATCH v3 6/7] examples/vhost: add an option " Yuanhan Liu
2016-10-09 7:28 ` [dpdk-dev] [PATCH v3 7/7] net/vhost: " Yuanhan Liu
2016-10-11 13:04 ` [dpdk-dev] [PATCH v3 0/7] vhost: add dequeue zero copy support Xu, Qian Q
2016-10-12 7:48 ` Yuanhan Liu
2016-10-09 10:46 ` [dpdk-dev] [PATCH 0/6] vhost: add Tx " linhaifeng
2016-10-10 8:03 ` Yuanhan Liu
2016-10-14 7:30 ` linhaifeng
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