On 11/21/2013 01:04 PM, Vlad Yasevich wrote: > e1000 provides a E1000_RAH_AV bit on every complete write > to the Receive Address Register. We can use this bit > 2 ways: > 1) To trigger HMP notifications. When the bit is set the > mac address is fully set and we can update the HMP. > > 2) We can turn off he bit on the write to low order bits of
s/he/the/
> the Receive Address Register, so that we would not try
> to match received traffic to this address when it is
> not completely set.
>
> Signed-off-by: Vlad Yasevich <vyase...@redhat.com>
> ---
> hw/net/e1000.c | 11 ++++++++++-
> 1 file changed, 10 insertions(+), 1 deletion(-)
>
>
> - if (index == RA || index == RA + 1) {
> + switch (index) {
> + case RA:
> + /* Mask off AV bit on the write of the low dword. The write of
> + * the high dword will set the bit. This way a half-written
> + * mac address will not be used to filter on rx.
> + */
> + s->mac_reg[RA+1] &= ~E1000_RAH_AV;
Does real hardware also auto-clear this bit when writing the low word
(thus forcing all drivers to write high word last to make a change take
effect)? Or are we risking the case of a driver that writes high word
first including the bit, and where real hardware just glitches over the
temporary half-written address where our emulation locks the user out
entirely? (Asked by someone that has not read the datasheet, so take
with a grain of salt)
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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