On Fri, Feb 06, 2015 at 01:46:36PM +0000, Stefan Hajnoczi wrote: > On Wed, Jan 07, 2015 at 04:08:29PM +0000, Stefan Hajnoczi wrote: > > On Thu, Dec 18, 2014 at 05:22:19PM +0800, Amos Kong wrote: > > > After enabled network debug of e1000 in Win2012-64r2 guest, > > > Bus mastering of e1000 can't be enabled by e1000 driver. It > > > caused guest can't get IP address. > > > > > > # bcdedit /debug on > > > # bcdedit /dbgsettings net hostip:192.168.122.100 port:50000 > > > (We can use non-existed IP here, it's just used to pass the > > > setup, not really use it) > > > > > > If we disable debug function, e1000 driver can enable bus > > > mastering bit successfully, guest network is fine. > > > > > > This patch changed e1000 backend to enalbe bus mastering > > > unconditionally as a workaround. > > > > > > Signed-off-by: Amos Kong <ak...@redhat.com> > > > --- > > > hw/net/e1000.c | 11 +++++++++-- > > > 1 file changed, 9 insertions(+), 2 deletions(-) > > > > > > diff --git a/hw/net/e1000.c b/hw/net/e1000.c > > > index ec9224b..82829ae 100644 > > > --- a/hw/net/e1000.c > > > +++ b/hw/net/e1000.c > > > @@ -1544,8 +1544,15 @@ static void e1000_write_config(PCIDevice *pci_dev, > > > uint32_t address, > > > > > > pci_default_write_config(pci_dev, address, val, len); > > > > > > - if (range_covers_byte(address, len, PCI_COMMAND) && > > > - (pci_dev->config[PCI_COMMAND] & PCI_COMMAND_MASTER)) { > > > + if (range_covers_byte(address, len, PCI_COMMAND)) { > > > + /* > > > + * Some guest (eg: Win2012-64r2) doesn't enable bus mastering > > > + * correctly, it caused guest network down. So we unconditionally > > > + * enable PCI bus mastering and BM memory region for e1000 as > > > + * a workaround. > > > + */ > > > + pci_dev->config[PCI_COMMAND] |= PCI_COMMAND_MASTER; > > > + memory_region_set_enabled(&pci_dev->bus_master_enable_region, > > > true); > > > qemu_flush_queued_packets(qemu_get_queue(s->nic)); > > > start_xmit(s); > > > } > > > > This is weird. > > > > Are you sure there's not some guest behavior missing like the NIC option > > ROM leaving bus mastering enabled after the BIOS/EFI has booted, causing > > Windows debug to work on physical machines?
QEMU emulated e1000 is too old, it's not in the official support list of window network debug. > > Before we merge a hack like this we should understand the problem 100%. > > Any new insights into what is going on here? It's not good to unconditionaly enable BM, we should enable/disable it according to other event/status change. > Stefan -- Amos.
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