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From: Stefano Brivio <sbrivio@redhat.com>
To: Laurent Vivier <lvivier@redhat.com>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v8 7/8] vhost-user: add vhost-user
Date: Thu, 14 Nov 2024 16:38:59 +0100	[thread overview]
Message-ID: <20241114163859.7eeafa38@elisabeth> (raw)
In-Reply-To: <b7aafab1-8eb6-462d-b492-21e51261179c@redhat.com>

On Thu, 14 Nov 2024 16:16:48 +0100
Laurent Vivier <lvivier@redhat.com> wrote:

> On 14/11/2024 15:23, Stefano Brivio wrote:
> > On Thu, 14 Nov 2024 11:20:09 +0100
> > Laurent Vivier <lvivier@redhat.com> wrote:
> >   
> >> On 17/10/2024 02:10, Stefano Brivio wrote:  
> >>>> +		if (frame_size == 0)
> >>>> +			first = &iov_vu[i + 1];
> >>>> +
> >>>> +		if (iov_vu[i + 1].iov_len > (size_t)len)
> >>>> +			iov_vu[i + 1].iov_len = len;
> >>>> +
> >>>> +		len -= iov_vu[i + 1].iov_len;
> >>>> +		iov_used++;
> >>>> +
> >>>> +		frame_size += iov_vu[i + 1].iov_len;
> >>>> +		num_buffers++;
> >>>> +
> >>>> +		if (frame_size >= mss || len == 0 ||
> >>>> +		    i + 1 == iov_cnt || !vu_has_feature(vdev, VIRTIO_NET_F_MRG_RXBUF)) {
> >>>> +			if (i + 1 == iov_cnt)
> >>>> +				check = NULL;
> >>>> +
> >>>> +			/* restore first iovec base: point to vnet header */
> >>>> +			vu_set_vnethdr(vdev, first, num_buffers, l2_hdrlen);
> >>>> +
> >>>> +			tcp_vu_prepare(c, conn, first, frame_size, &check);
> >>>> +			if (*c->pcap)  {
> >>>> +				tcp_vu_update_check(tapside, first, num_buffers);
> >>>> +				pcap_iov(first, num_buffers,
> >>>> +					 sizeof(struct virtio_net_hdr_mrg_rxbuf));
> >>>> +			}
> >>>> +
> >>>> +			conn->seq_to_tap += frame_size;  
> >>> We always increase this, even if, later...
> >>>      
> >>>> +
> >>>> +			frame_size = 0;
> >>>> +			num_buffers = 0;
> >>>> +		}
> >>>> +	}
> >>>> +
> >>>> +	/* release unused buffers */
> >>>> +	vu_queue_rewind(vq, iov_cnt - iov_used);
> >>>> +
> >>>> +	/* send packets */
> >>>> +	vu_flush(vdev, vq, elem, iov_used);  
> >>> we fail to send packets, that is, even if vu_queue_fill_by_index()
> >>> returns early because (!vq->vring.avail).  
> >>
> >> vring.avail is a pointer to a structure. vring.avail is NULL if there is something wrong
> >> during the initialization. It's imported code, I think it's only a sanity check.
> >> So in theory vu_flush() cannot fail.  
> > 
> > Oh, I see now. I actually think it's preferable to crash in that
> > (theoretically impossible) case, without even an ASSERT() (we would
> > dereference a NULL pointer, eventually, even if not here).
> 
> So what you propose is to remove the "if (!vq->vring.avail) return;"?

Yes, all of them, actually. It also avoids confusion I think.

-- 
Stefano


  reply	other threads:[~2024-11-14 15:39 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2024-10-10 12:28 [PATCH v8 0/8] Add vhost-user support to passt. (part 3) Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 1/8] packet: replace struct desc by struct iovec Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 2/8] vhost-user: introduce virtio API Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 3/8] vhost-user: introduce vhost-user API Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 4/8] udp: Prepare udp.c to be shared with vhost-user Laurent Vivier
2024-10-14  4:29   ` David Gibson
2024-10-10 12:28 ` [PATCH v8 5/8] tcp: Export headers functions Laurent Vivier
2024-10-14  4:29   ` David Gibson
2024-10-10 12:29 ` [PATCH v8 6/8] passt: rename tap_sock_init() to tap_backend_init() Laurent Vivier
2024-10-14  4:30   ` David Gibson
2024-10-14 22:38   ` Stefano Brivio
2024-10-10 12:29 ` [PATCH v8 7/8] vhost-user: add vhost-user Laurent Vivier
2024-10-15  3:23   ` David Gibson
2024-10-16 10:07     ` Laurent Vivier
2024-10-16 16:26       ` Stefano Brivio
2024-10-15 19:54   ` Stefano Brivio
2024-10-16  0:41     ` David Gibson
2024-10-17  0:10       ` Stefano Brivio
2024-10-17 11:25         ` Stefano Brivio
2024-10-17 11:54           ` Laurent Vivier
2024-10-17 17:18           ` Laurent Vivier
2024-10-17 17:25             ` Laurent Vivier
2024-10-17 17:33             ` Stefano Brivio
2024-10-17 21:21               ` Stefano Brivio
2024-10-22 12:59         ` Laurent Vivier
2024-10-22 13:19           ` Stefano Brivio
2024-10-22 18:19             ` Stefano Brivio
2024-10-22 18:22               ` Stefano Brivio
2024-10-23 15:27           ` Laurent Vivier
2024-10-23 16:23             ` Stefano Brivio
2024-10-17  0:10   ` Stefano Brivio
2024-10-17  7:28     ` Laurent Vivier
2024-10-17  8:33       ` Stefano Brivio
2024-11-14 10:20     ` Laurent Vivier
2024-11-14 14:23       ` Stefano Brivio
2024-11-14 15:16         ` Laurent Vivier
2024-11-14 15:38           ` Stefano Brivio [this message]
2024-11-14 10:23     ` Laurent Vivier
2024-11-14 14:23       ` Stefano Brivio
2024-11-15  8:30         ` Laurent Vivier
2024-11-15 10:08           ` Stefano Brivio
2024-11-14 10:29     ` Laurent Vivier
2024-11-14 14:23       ` Stefano Brivio
2024-11-15 11:13         ` Laurent Vivier
2024-11-15 11:23           ` Stefano Brivio
2024-10-10 12:29 ` [PATCH v8 8/8] test: Add tests for passt in vhost-user mode Laurent Vivier
2024-10-15  3:40   ` David Gibson
2024-10-15 19:54   ` Stefano Brivio
2024-10-16  8:06     ` Laurent Vivier
2024-10-16  9:47       ` Stefano Brivio

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