From mboxrd@z Thu Jan  1 00:00:00 1970
From: "Xie, Huawei" <huawei.xie@intel.com>
Subject: Re: [PATCH 2/4] vhost: introduce vhost_log_write
Date: Wed, 9 Dec 2015 05:44:11 +0000
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Cc: "dev@dpdk.org" <dev@dpdk.org>, Victor Kaplansky <victork@redhat.com>,
 "Michael S. Tsirkin" <mst@redhat.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
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On 12/9/2015 11:41 AM, Yuanhan Liu wrote:=0A=
> On Wed, Dec 09, 2015 at 03:33:16AM +0000, Xie, Huawei wrote:=0A=
> ...=0A=
>>>> +static inline void __attribute__((always_inline))=0A=
>>>> +vhost_log_write(struct virtio_net *dev, struct vhost_virtqueue *vq,=
=0A=
>>>> +		uint64_t offset, uint64_t len)=0A=
>>>> +{=0A=
>>>> +	uint64_t addr =3D vq->log_guest_addr;=0A=
>>>> +	uint64_t page;=0A=
>>>> +=0A=
>>>> +	if (unlikely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) =3D=3D 0) =
||=0A=
>>>> +		     !dev->log_base || !len))=0A=
>>>> +		return;=0A=
>>> Isn't "likely" more appropriate in above, since the whole=0A=
>>> expression is expected to be true most of the time?=0A=
>> Victor:=0A=
>> So we are not always logging, what is the message that tells the backend=
=0A=
>> the migration is started?=0A=
> When log starts, VHOST_USER_SET_FEATURES request will be sent again,=0A=
> with VHOST_F_LOG_ALL feature bit set.=0A=
As the VHOST_USER_SET_FEATURES handling and rx/tx runs asynchronously,=0A=
we have to make sure we don't miss logging anything when this feature is=0A=
set. For example, I doubt like in virtio_dev_rx, is the dev->features=0A=
volatile?=0A=
> 	--yliu=0A=
>=0A=
=0A=