Re: [Xen-devel] [PATCH QEMU-XEN] xen/pt: Start with emulated PCI_COMMAND set to zero.

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 10.06.15 at 22:53, <konrad@xxxxxxxxxx> wrote:
> --- a/hw/xen/xen_pt.c
> +++ b/hw/xen/xen_pt.c
> @@ -785,7 +785,9 @@ out:
>          xen_host_pci_set_word(&s->real_device, PCI_COMMAND,
>                                pci_get_word(d->config + PCI_COMMAND) | cmd);
>      }
> -
> +    /* Until the guest enables the device use d->config values which will
> +     * inhibit pci_bar_address & pci_update_mappings from triggering 
> updates.*/
> +    pci_set_word(d->config + PCI_COMMAND, 0);
>      memory_listener_register(&s->memory_listener, &address_space_memory);
>      memory_listener_register(&s->io_listener, &address_space_io);
>      XEN_PT_LOG(d,

Well, I can see this as something to be tried out as an experiment,
but it looks like you mean this to be a proper submission for
inclusion upstream? Or maybe not, considering that qemu-devel
wasn't even Cc-ed? In any case - what we need here is a general
solution to at least the initialization part of the problem, i.e. all
fields we emulate some or all bits for need to have d->config[]
updated accordingly (i.e. you need to merge d->config[] and
XenPTReg's data field based on the respective XenPTRegInfo's
emu_mask, but perhaps simply copying the data field to
d->config[] would have the same effect; if it doesn't, we have
yet another problem). For the command register this for example
means that it is in no way guaranteed that it would end up being
zero; its emu_mask however guarantees that the memory and I/O
decode bits would start out as zero (which is what you're after).

Jan


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