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Date: Wed, 9 Dec 2015 16:41:36 +0800
From: Yuanhan Liu <yuanhan.liu@linux.intel.com>
To: "Xie, Huawei" <huawei.xie@intel.com>
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Cc: "dev@dpdk.org" <dev@dpdk.org>, Victor Kaplansky <victork@redhat.com>,
"Michael S. Tsirkin" <mst@redhat.com>
Subject: Re: [dpdk-dev] [PATCH 2/4] vhost: introduce vhost_log_write
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On Wed, Dec 09, 2015 at 05:44:11AM +0000, Xie, Huawei wrote:
> On 12/9/2015 11:41 AM, Yuanhan Liu wrote:
> > On Wed, Dec 09, 2015 at 03:33:16AM +0000, Xie, Huawei wrote:
> > ...
> >>>> +static inline void __attribute__((always_inline))
> >>>> +vhost_log_write(struct virtio_net *dev, struct vhost_virtqueue *vq,
> >>>> + uint64_t offset, uint64_t len)
> >>>> +{
> >>>> + uint64_t addr = vq->log_guest_addr;
> >>>> + uint64_t page;
> >>>> +
> >>>> + if (unlikely(((dev->features & (1ULL << VHOST_F_LOG_ALL)) == 0) ||
> >>>> + !dev->log_base || !len))
> >>>> + return;
> >>> Isn't "likely" more appropriate in above, since the whole
> >>> expression is expected to be true most of the time?
> >> Victor:
> >> So we are not always logging, what is the message that tells the backend
> >> the migration is started?
> > When log starts, VHOST_USER_SET_FEATURES request will be sent again,
> > with VHOST_F_LOG_ALL feature bit set.
> As the VHOST_USER_SET_FEATURES handling and rx/tx runs asynchronously,
> we have to make sure we don't miss logging anything when this feature is
> set.
That's a good remind. Thanks.
> For example, I doubt like in virtio_dev_rx, is the dev->features
> volatile?
No, it is not volatile.
--yliu