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From: Jiahuan Zhang <jiahuanzhang90@gmail.com>
Date: Wed, 19 Apr 2017 15:34:36 +0200
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Subject: Re: [Qemu-devel] Hight Processor time of Socket communciation
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To: Peter Maydell <peter.maydell@linaro.org>
Cc: QEMU Developers <qemu-devel@nongnu.org>

On 19 April 2017 at 12:09, Peter Maydell <peter.maydell@linaro.org> wrote:

> On 19 April 2017 at 11:04, Jiahuan Zhang <jiahuanzhang90@gmail.com> wrote:
> > Okay. Thank you for pointing this out.
> > I would like to make a new serial device based on pl011,
> > but containing a buffer for guest-to-host data transfer.
>
> As I've said, the PL011 is inherently byte at a time.
> If you want better than that, I recommend you use virtio-serial,
> because it already exists for this purpose.
>
> thanks
> -- PMM
>

Hi Peter,

But from the source code, I found the main characteristic of virtio-serial
is that,
virtio-serial can create multiple serial ports and each port has a pair of
control virt-queues and
a pair of guest input/output virt-queues.
Its "have_data" callback function enables multi-byte data transfer from
guest.
And it is not in a tranditional device emulation format.
I mean that no exact IO region is emulated for it.
Without Linux kernel driver, I don't know how to manipulate it.
For the time being, I enable the guest app to send data to
the pl011's data register directly via a pointer, as you see that in the
code above.

This is why I am thinking if adding a transmit buffer in pl011 for guest
writing
is a feasible alternative.

Any suggestion is welcome.
Regards,
Huan