Re: [Qemu-devel] [PATCH v2] Fix buffer run out in eepro100.

[Stefan Weil <sw@weilnetz.de>]

Am 29.08.2012 13:26, schrieb Bo Yang:
> This is reported by QA. When installing os with pxe, after the initial
> kernel and initrd are loaded, the procedure tries to copy files from install
> server to local harddisk, the network becomes stall because of running out of
> receive descriptor.
>
> Signed-off-by: Bo Yang<boyang@suse.com>
> ---
>   hw/eepro100.c |    5 ++++-
>   1 files changed, 4 insertions(+), 1 deletions(-)
>
> diff --git a/hw/eepro100.c b/hw/eepro100.c
> index 50d117e..52a18ad 100644
> --- a/hw/eepro100.c
> +++ b/hw/eepro100.c
> @@ -1036,6 +1036,8 @@ static void eepro100_ru_command(EEPRO100State * s, uint8_t val)
>           }
>           set_ru_state(s, ru_ready);
>           s->ru_offset = e100_read_reg4(s, SCBPointer);
> +    	qemu_flush_queued_packets(&s->nic->nc);
> +	qemu_notify_event();

What would happen if the above changes were omitted?
Would the network show less performance? How much
would the test scenario (Linux installation) take longer?

What about the other nic emulations in QEMU?
I observe hanging network rather often with the
ARM versatilepb emulation.

>           TRACE(OTHER, logout("val=0x%02x (rx start)\n", val));
>           break;
>       case RX_RESUME:
> @@ -1770,7 +1772,8 @@ static ssize_t nic_receive(NetClientState *nc, const uint8_t * buf, size_t size)
>       if (rfd_command&  COMMAND_EL) {
>           /* EL bit is set, so this was the last frame. */
>           logout("receive: Running out of frames\n");
> -        set_ru_state(s, ru_suspended);
> +        set_ru_state(s, ru_no_resources);
> +	eepro100_rnr_interrupt(s);

Adding the interrupt here is correct (I have similar code in
http://repo.or.cz/w/qemu/ar7.git/blob/HEAD:/hw/eepro100.c
which is an improved version of hw/eepro100.c).

Setting ru_no_resources looks also good, but I am not
sure whether removing ru_suspended is ok. Maybe it should
be ru_no_resources | ru_suspended.

>       }
>       if (rfd_command&  COMMAND_S) {
>           /* S bit is set. */

It's interesting to hear that your QA tests with eepro100.c.
Which nic model do they use in their tests?

Regards,

Stefan W.