Re: [Xen-devel] Question about HVM network

[cc Luit <universalbillow@xxxxxxxxx>]

On Mon, Nov 7, 2011 at 5:57 PM, Ian Campbell <Ian.Campbell@xxxxxxxxxx> wrote:

On Sun, 2011-11-06 at 14:12 +0000, cc Luit wrote:
> Hi, all,
>
>
> I've a question about how network of HVM works,
> when hvm startup, I found the qemu register the io port 0xc100-0xc1ff
> to the function rtl8139_ioport_write, is this means qemu emulate the
> rtl8139 NIC to handle network io event?

> I think this is the default. You can select a different emulated NIC
> using e.g. "model=e1000" in your VIF stanza in the guest configuration
> file.

> but when I scp a file to the remote machine, I cannot find any write
> to these ports, so I'm curious how hvm's network works?

> Perhaps you have ended up with PVHVM network driver? This will take
> precedence to the emulated NIC if present.

Thanks, then can you tell me how PVHVM works, and how can I know if I use it?

and I digged into the rtl8139's driver codes and emulated one in qemu-tools, I found that the hvm use the mmio rather than pio to inform the NIC to poll the descriptor, I think that's why there is no write to the port io, but I'm still curious why qemu need to register the ports to those functions?

Ian.

>
>
> first I'm not using the passthrough, so I think that it will use DMA:
> after it write the content to the memory, it will use PIO to write to
> one of the port to tell the qemu it need to start DMA, but there is no
> write to the port, then how does the rtc8139 emulated by qemu know
> when to start the DMA and where is the memory address?
>
>
> hope someone can help me~ thanks in advance.
>
>
> --
> - Luit @ Parallel Processing Institute, Fudan University
>

-- 
- Luit @ Parallel Processing Institute, Fudan University 
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