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

[Michael S. Tsirkin]

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 ...

> >>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?

> >
> >>---
> >>  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 */