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Date: Fri, 14 Sep 2012 09:34:59 +0800
From: Amos Kong <akong@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v2] rtl8139: implement 8139cp link status
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To: Stefan Hajnoczi <stefanha@gmail.com>
Cc: jasowang@redhat.com, mst@redhat.com, aliguori@us.ibm.com, stefanha@linux.vnet.ibm.com, qemu-devel@nongnu.org

On 13/09/12 20:29, Stefan Hajnoczi wrote:
> On Thu, Sep 13, 2012 at 9:51 AM, Amos Kong <akong@redhat.com> wrote:
>> From: Jason Wang <jasowang@redhat.com>
>>
>> Add a link status chang callback and change the link status bit in BMSR
>> & MSR accordingly. Tested in Linux/Windows guests.
>>
>> The link status bit of MediaStatus is infered from BasicModeStatus,
>> they are reverse.
>>
>> Signed-off-by: Jason Wang <jasowang@redhat.com>
>> Signed-off-by: Amos Kong <akong@redhat.com>
>> ---
>> v2: don't add MediaState in RTL8139State to avoid migration trouble
>> ---
>>   hw/rtl8139.c |   19 +++++++++++++++++--
>>   1 files changed, 17 insertions(+), 2 deletions(-)
>>
>> diff --git a/hw/rtl8139.c b/hw/rtl8139.c
>> index 844f1b8..fa949ca 100644
>> --- a/hw/rtl8139.c
>> +++ b/hw/rtl8139.c
>> @@ -167,7 +167,7 @@ enum IntrStatusBits {
>>       PCIErr = 0x8000,
>>       PCSTimeout = 0x4000,
>>       RxFIFOOver = 0x40,
>> -    RxUnderrun = 0x20,
>> +    RxUnderrun = 0x20, /* Packet Underrun / Link Change */
>>       RxOverflow = 0x10,
>>       TxErr = 0x08,
>>       TxOK = 0x04,
>> @@ -3007,7 +3007,7 @@ static uint32_t rtl8139_io_readb(void *opaque, uint8_t addr)
>>               break;
>>
>>           case MediaStatus:
>> -            ret = 0xd0;
>> +            ret = 0xd0 | ~(s->BasicModeStatus & 0x0004);
>>               DPRINTF("MediaStatus read 0x%x\n", ret);
>>               break;
>
> This does not give any hint that BMSR & 0x4 is the link status
> (inverted).

only mentioned in the commitlog, will add a comment here.

> I suggest adding an enum like the other constants at the
> top of the file:
>
> ret = 0xd0 | (nc->link_down ? MSRLinkDown : 0);

Ok, I will update the patch.

> Regarding migration: do we migrate the NetClient->link_down field? If
> we only migrate the status register value then the link may actually
> be up at the net.c level.

I tried to add 'MediaStatus' to 'struct RTL8139State', and update
'VMStateDescription vmstate_rtl8139', then the value of MediaStatus
will be migrated.

But the idea in v2 is better.

> Stefan

Thanks.

-- 
			Amos.