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Date: Wed, 06 Aug 2008 09:13:15 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH] only check RCTL_EN in e1000_can_receive()
References: <g7adi4$as5$1@ger.gmane.org>
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To: qemu-devel@nongnu.org

Charles Duffy wrote:
> e1000_receive() has code to raise a receive overflow interrupt when 
> the receive buffer head and tail match. However, with the present 
> implementation of e1000_can_receive(), this code is unreachable -- and 
> etherboot breaks as a result.
>
> The attached quick-and-dirty patch fixes etherboot for e1000, and does 
> not appear to break post-boot functionality.

While this is a legitimate bug, it's probably only present in KVM or 
when using the slirp rate limiting.  Right in QEMU, a can_receive 
handler for a network card is largely ignored whereas in KVM, it is used 
to throttle receive for the tap device.

Nonetheless, the correct behaviour is to raise an interrupt when a 
packet could be received but no buffers are available so I've applied 
this patch.  Thanks.

Regards,

Anthony Liguori