* Re: [PATCH] virtio_balloon: check virtqueue_add_outbuf() return value [not found] <4789cbbb9d59420abc86a9e225ef0bfd@inspur.com> @ 2022-05-27 10:57 ` Michael S. Tsirkin 0 siblings, 0 replies; 3+ messages in thread From: Michael S. Tsirkin @ 2022-05-27 10:57 UTC (permalink / raw) To: Bo Liu (刘波)-浪潮信息 Cc: virtualization@lists.linux-foundation.org, linux-kernel@vger.kernel.org On Fri, May 27, 2022 at 10:43:30AM +0000, Bo Liu (刘波)-浪潮信息 wrote: > The purpose of this patch is, virtqueue_add_outbuf() adding data to > virtqueue may succeed or fail. If successful, it will call virtqueue_kick() > to notifie the host backend driver, but if the virtqueue_add_outbuf() fails, > the data is not successfully added to the virtqueue, and the host back-end > driver does not need to be notified for processing. > > Thanks. Why is it a problem if we do? -- MST _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 3+ messages in thread
[parent not found: <7a413652a9a9469f948fbfa2eae5c401@inspur.com>]
* Re: [PATCH] virtio_balloon: check virtqueue_add_outbuf() return value [not found] <7a413652a9a9469f948fbfa2eae5c401@inspur.com> @ 2022-05-30 7:00 ` David Hildenbrand 0 siblings, 0 replies; 3+ messages in thread From: David Hildenbrand @ 2022-05-30 7:00 UTC (permalink / raw) To: Bo Liu (刘波)-浪潮信息, mst@redhat.com Cc: linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org On 30.05.22 04:16, Bo Liu (刘波)-浪潮信息 wrote: > Adding this patch can avoid unnecessary VM exits and reduce the number of VM exits > ... in corner cases where virtqueue_add_outbuf() fails? Why do we care about that corner case? Looks like unnecessary code churn to me, unless I am missing something important. -- Thanks, David / dhildenb _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 3+ messages in thread
[parent not found: <20220527013401.2196-1-liubo03@inspur.com>]
* Re: [PATCH] virtio_balloon: check virtqueue_add_outbuf() return value [not found] <20220527013401.2196-1-liubo03@inspur.com> @ 2022-05-27 10:24 ` Michael S. Tsirkin 0 siblings, 0 replies; 3+ messages in thread From: Michael S. Tsirkin @ 2022-05-27 10:24 UTC (permalink / raw) To: Bo Liu; +Cc: virtualization, linux-kernel On Thu, May 26, 2022 at 09:34:01PM -0400, Bo Liu wrote: > virtqueue_add_outbuf() can fail, when it fails, there is no need > to call the funciont virtqueue_kick(). > Signed-off-by: Bo Liu <liubo03@inspur.com> Sorry don't get it. What's the point of this patch really? > --- > drivers/virtio/virtio_balloon.c | 18 +++++++++++------- > 1 file changed, 11 insertions(+), 7 deletions(-) > > diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c > index b9737da6c4dd..0d7da4d95e1e 100644 > --- a/drivers/virtio/virtio_balloon.c > +++ b/drivers/virtio/virtio_balloon.c > @@ -153,16 +153,18 @@ static void tell_host(struct virtio_balloon *vb, struct virtqueue *vq) > { > struct scatterlist sg; > unsigned int len; > + int err; > > sg_init_one(&sg, vb->pfns, sizeof(vb->pfns[0]) * vb->num_pfns); > > /* We should always be able to add one buffer to an empty queue. */ > - virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); > - virtqueue_kick(vq); > - > - /* When host has read buffer, this completes via balloon_ack */ > - wait_event(vb->acked, virtqueue_get_buf(vq, &len)); > + err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); > + if (!err) { > + virtqueue_kick(vq); > > + /* When host has read buffer, this completes via balloon_ack */ > + wait_event(vb->acked, virtqueue_get_buf(vq, &len)); > + } > } > > static int virtballoon_free_page_report(struct page_reporting_dev_info *pr_dev_info, > @@ -382,6 +384,7 @@ static void stats_handle_request(struct virtio_balloon *vb) > struct virtqueue *vq; > struct scatterlist sg; > unsigned int len, num_stats; > + int err; > > num_stats = update_balloon_stats(vb); > > @@ -389,8 +392,9 @@ static void stats_handle_request(struct virtio_balloon *vb) > if (!virtqueue_get_buf(vq, &len)) > return; > sg_init_one(&sg, vb->stats, sizeof(vb->stats[0]) * num_stats); > - virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); > - virtqueue_kick(vq); > + err = virtqueue_add_outbuf(vq, &sg, 1, vb, GFP_KERNEL); > + if (!err) > + virtqueue_kick(vq); > } > > static inline s64 towards_target(struct virtio_balloon *vb) > -- > 2.27.0 _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization ^ permalink raw reply [flat|nested] 3+ messages in thread
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[not found] <4789cbbb9d59420abc86a9e225ef0bfd@inspur.com>
2022-05-27 10:57 ` [PATCH] virtio_balloon: check virtqueue_add_outbuf() return value Michael S. Tsirkin
[not found] <7a413652a9a9469f948fbfa2eae5c401@inspur.com>
2022-05-30 7:00 ` David Hildenbrand
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2022-05-27 10:24 ` Michael S. Tsirkin
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