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> + > + /* > + * Reset the command register: it is possible that when passing > + * through a PCI device its memory decoding bits in the command > + * register are already set. Thus, a guest OS may not write to the > + * command register to update memory decoding, so guest mappings > + * (guest's view of the BARs) are left not updated. > + */ > + pci_conf_write16(pdev->sbdf, PCI_COMMAND, 0); Can you really blindly write 0 here? What about bits that have to be under host control, e.g. INTX_DISABLE? I can see that you may want to hand off with I/O and memory decoding off and bus mastering disabled, but for every other bit (including reserved ones) I'd expect separate justification (in the commit message). Jan