Re: Intention to work on GSoC project

[Sahil <icegambit91@gmail.com>]

Hi,

Thank you for your reply.

On Friday, March 15, 2024 4:57:39 PM IST Eugenio Perez Martin wrote:
> [...]
> > Some sections in the above docs were difficult to grasp. For the time
> > being, I have focused on those parts that I thought were relevant
> > to the project.
> 
> Please feel free to ask any questions, maybe we can improve the doc :).

I understood the introductory sections of the documentation such as the
"About QEMU" section and the first half of the "system emulation". Sections
and subsections that went into greater detail were a little overwhelming
such as the "QEMU virtio-net standby" subsection [1] or the "migration
features" [2] subsection. But the red hat blogs and deep-dive articles helped
cover a lot of ground conceptually.

I feel once I start getting my hands dirty, I'll be able to absorb these concepts
much better.

I did have two questions that I would like to ask.

Q1.
Regarding the "Deep dive into Virtio-networking and vhost-net" article [3],
the "Introduction" subsection of the "Vhost protocol" section mentions that
sending the available buffer notification involves a vCPU interrupt (4th bullet
point). But in figure 2, the arrow for the "available buffer notification" indicates
a PCI interrupt. Initially I thought they were two different interrupts but I am
a little confused about this now.

Q2.
In the "Virtio-net failover operation" section of the "Virtio-net failover: An
introduction" article [4], there are five bullet points under the first figure.
The second point states that the guest kernel needs the ability to switch
between the VFIO device and the vfio-net device. I was wondering if
"vfio-net" is a typo and if it should be "virtio-net" instead.

> [...]
> There is a post before the first in the series:
> https://www.redhat.com/en/blog/virtio-devices-and-drivers-overview-headjack-
> and-phone

Got it. I didn't know this was the first in the series. I have now covered this as
well, so I can move on to "Virtqueues and virtio ring: How the data travels" [3] :)

> > 1. Virtqueues and virtio ring: How the data travels [8]
> > 2. Packed virtqueue: How to reduce overhead with virtio [9]
> > 3. Virtio live migration technical deep dive [10]
> > 4. Hands on vDPA: what do you do when you ain't got the hardware v2 (Part
> > 1) [11]
> I think it's a good plan!
> 
> If you feel like you're reading a lot of theory and want to get your
> hands dirty already, you can also start messing with the code with the
> blogs you already read. Or, maybe, after reading the Packed virtqueue
> one, your call.
> 
> In a very brute-forced description, you can start trying to copy all
> the *packed* stuff of kernel's drivers/virtio/virtio_ring.c into
> vhost_shadow_virtqueue.c.

I would love to start with some hands-on tasks. I'll take a look at
the kernel's "drivers/virtio/virtio_ring.c". I think I should also start
going through the "vhost_shadow_virtqueue.c" [4] source code.

> There is a lot more in the task, and I can get into more detail
> if you want either here or in a meeting.

Thank you. Either means of communication works for me although
the latter will require some coordination.

> If you prefer to continue with the theory it is ok too.

A good balance of theory and practice would be nice at this stage.
It'll keep my brains from getting too muddled up.

Thanks,
Sahil

[1] https://www.qemu.org/docs/master/system/virtio-net-failover.html
[2] https://www.qemu.org/docs/master/devel/migration/features.html
[3] https://www.redhat.com/en/blog/deep-dive-virtio-networking-and-vhost-net
[4] https://www.redhat.com/en/blog/virtio-net-failover-introduction
[5] https://www.redhat.com/en/blog/virtqueues-and-virtio-ring-how-data-travels