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From: HePeng <xnhp0320@icloud.com>
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Date: Fri, 15 Jun 2018 21:28:13 +0800
Cc: Ilya Maximets <i.maximets@samsung.com>, dev@dpdk.org,
 Tiwei Bie <tiwei.bie@intel.com>, Zhihong Wang <zhihong.wang@intel.com>
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To: Maxime Coquelin <maxime.coquelin@redhat.com>
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Subject: Re: [dpdk-dev] Missing an increment on vq->log_cache_nb_elem ?
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Hi, Maxime,

  My name is Peng He.=20

  Thanks.=20

> =D4=DA 2018=C4=EA6=D4=C215=C8=D5=A3=AC=CF=C2=CE=E79:24=A3=ACMaxime =
Coquelin <maxime.coquelin@redhat.com> =D0=B4=B5=C0=A3=BA
>=20
> Hi,
>=20
> On 06/15/2018 02:32 PM, Ilya Maximets wrote:
>>> Hi,
>>>=20
>>>=20
>>> In the latest dpdk master branch, in the function =
*vhost_log_cache_page*:
>>>=20
>>>=20
>>> static __rte_always_inline void
>>> vhost_log_cache_page(struct virtio_net *dev, struct vhost_virtqueue =
*vq,
>>> 			uint64_t page)
>>> {
>>> 	uint32_t bit_nr =3D page % (sizeof(unsigned long) << 3);
>>> 	uint32_t offset =3D page / (sizeof(unsigned long) << 3);
>>> 	int i;
>>>=20
>>> 	for (i =3D 0; i < vq->log_cache_nb_elem; i++) {
>>> 		struct log_cache_entry *elem =3D vq->log_cache + i;
>>>=20
>>> 		if (elem->offset =3D=3D offset) {
>>> 			elem->val |=3D (1UL << bit_nr);
>>> 			return;
>>> 		}
>>> 	}
>>>=20
>>> 	if (unlikely(i >=3D VHOST_LOG_CACHE_NR)) {
>>> 		/*
>>> 		 * No more room for a new log cache entry,
>>> 		 * so write the dirty log map directly.
>>> 		 */
>>> 		rte_smp_wmb();
>>> 		vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, =
page);
>>>=20
>>> 		return;
>>> 	}
>>>=20
>>> 	vq->log_cache[i].offset =3D offset;
>>> 	vq->log_cache[i].val =3D (1UL << bit_nr);
>>> }
>>>=20
>>> Did it just miss an increment on vq->log_cache_nb_elem ?
>> Hi. Thanks for pointing that.
>> I looked through the code and I see no updates of =
'vq->log_cache_nb_elem'.
>> Looks like it always equal to initial zero value.
>> Maxime, I'm afraid that this means that currently pages logging is =
not
>> performed at all. Could you please check?
>> Best regards, Ilya Maximets.
>=20
> Thanks Ilya for the heads-up and HePeng for reporting the issue.
> It is broken indeed... We didn't noticed corruption when running
> our non-reg tests, I guess they have to be improved.
>=20
> I will post a patch shortly to fix this.
>=20
> HePeng, how does your name spells in the form "$firstname $lastname"?
> I would need this info to credit you for reporting the issue.
>=20
> Regards,
> Maxime