Re: Questions about virtio DMA operations

[Peter Maydell]

On Sun, 29 Aug 2021 at 04:48, Arnabjyoti Kalita
<akalita@cs.stonybrook.edu> wrote:
>
> Thank you for the detailed explanation, Peter. It makes a lot of things clear 
> now.
>
> I see that the virtio block device is accessing guest physical memory that is 
> not backed by a device.

That's normal, yes, but you can't guarantee it. The guest can
choose to program it to any physical memory it likes.

> Since I'm not doing a live migration, nor I am hot-unplugging the
> memory DIMM and I just want "used" virtqueue buffers be written
> to the guest memory, I can possibly just move forward without doing
> an unmap() in this case.

I'm not clear on what you're trying to do, but this doesn't
sound like the right way to go to me.

-- PMM