[gPXE] [Etherboot-developers] [PATCH] [pciextra] Restore the PCI COMMAND register after writing to the BARs

[Stefan Hajnoczi]

Hi Bernhard,
I hope we can debug this further to understand exactly what is going on here.

Have you tried running gPXE on the same hardware without KVM?

> We got problems when using gPXE in KVM virtual machines with direct PCI device access.

What happens when you run gPXE?  Does the network device fail to come
up?  Does the VM hang?

Which devices are giving you this problem?  Which versions of KVM,
Linux, and gPXE are you using?

I'd like to see what changed prior to restoring the command register:

uint16_t cmd_after;
pci_read_config_word ( pci, PCI_COMMAND, &cmd_after );
DBG ( "pci_bar_size before=0x%x after=0x%x\n", cmd, cmd_after );

If you build with "make DEBUG=pciextra" then you'll get this debug output.

Stefan