Re: [Qemu-devel] [PATCH] Revert "rtl8139: do the network/host communication only in normal operating mode"

[Jason Wang]

On 05/10/2012 07:05 PM, Michael S. Tsirkin wrote:
> On Thu, May 10, 2012 at 05:31:56PM +0800, Jason Wang wrote:
> > On 05/10/2012 04:54 PM, Michael S. Tsirkin wrote:
> > > On Thu, May 10, 2012 at 04:37:22PM +0800, Jason Wang wrote:
> > > > This reverts commit ff71f2e8cacefae99179993204172bc65e4303df. This is because
> > > > the linux 8139cp driver would leave the card in "Config Register Write Enable"
> > > > mode after the eeprom were read or write ( which is unexpected in the spec
> > > > ).
> > > Could you show where this happens please?
> > Hi Michael:
> >
> > According to the spec:
> > """
> > Normal(0x00): RTL8139C(L)+ network/host communication mode.
> > ...
> > Config. Register Write Enable(0x11): Before writing to the CONFIG0,
> > 1, 3, 4 registers, and bits 13, 12, 8 of BMCR (offset 62h-63h), the
> > RTL8139C(L)+ must be placed in this mode. This will protect the
> > RTL8139C(L)+ configuration from accidental change.
> > """
> > So If I am reading it correctly, guest should place the card in
> > "Normal mode" during transmission and reception. But linux driver
> > would reset the mode to 11 after each read or write to the eeprom,
> > see eeprom_cmd_end() in 8139cp.c.
> Which version? The one I see upstream just clears chip select ...

It use writeb(), so in the meantime it also set the high two bits of 9346.
> > > > Also a physical 8139 card can still DMA into host memory in modes other than
> > > > Normal mode, so we need revert this commit to align with the behavior of
> > > > physical card.
> > > >
> > > > The issue of 8139cp driver should be fixed in linux seperately.
> > > >
> > > > Signed-off-by: Jason Wang<address@hidden>
> > > It's admittedly a bit of a hack but I thought the point is
> > > to work with unmodified drivers?
> > Yes, and as the physical 8139 card would still doing transmission
> > and reception when it's not in normal mode, so we need revert this
> > patch to let unmodified driver work.
> But it *won't* work - the reason we applied this hack is
> because guest memory got corrupted because of
> the guest bug. eeprom writes are rare enough so this
> seems like the lesser evil.
>
> > > What do windows drivers do? Can you check pls?
> > Windows guest would let the card in normal mode after eeprom access.
> Does it have the rx ring programming bug too?

It does not have such a bug according to debug log.
> > > > ---
> > > >   hw/rtl8139.c |    9 ---------
> > > >   1 files changed, 0 insertions(+), 9 deletions(-)
> > > >
> > > > diff --git a/hw/rtl8139.c b/hw/rtl8139.c
> > > > index eb22d04..2413bc3 100644
> > > > --- a/hw/rtl8139.c
> > > > +++ b/hw/rtl8139.c
> > > > @@ -791,9 +791,6 @@ static int rtl8139_can_receive(VLANClientState *nc)
> > > >         return 1;
> > > >       if (!rtl8139_receiver_enabled(s))
> > > >         return 1;
> > > > -    /* network/host communication happens only in normal mode */
> > > > -    if ((s->Cfg9346&   Chip9346_op_mask) != Cfg9346_Normal)
> > > > -       return 0;
> > > >
> > > >       if (rtl8139_cp_receiver_enabled(s)) {
> > > >           /* ??? Flow control not implemented in c+ mode.
> > > > @@ -836,12 +833,6 @@ static ssize_t rtl8139_do_receive(VLANClientState *nc, 
> > > > const uint8_t *buf, size_
> > > >           return -1;
> > > >       }
> > > >
> > > > -    /* check whether we are in normal mode */
> > > > -    if ((s->Cfg9346&   Chip9346_op_mask) != Cfg9346_Normal) {
> > > > -        DPRINTF("not in normal op mode\n");
> > > > -        return -1;
> > > > -    }
> > > > -
> > > >       /* XXX: check this */
> > > >       if (s->RxConfig&   AcceptAllPhys) {
> > > >           /* promiscuous: receive all */