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

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Mon, Jun 15, 2015 at 05:19:09PM +0100, Stefano Stabellini wrote:
> On Thu, 11 Jun 2015, Jan Beulich wrote:
> > >>> On 10.06.15 at 22:53, <konrad@kernel.org> 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).
> 
> I am not sure I can ask Konrad to come up with a larger general solution
> when his intent was just to fix this issue.  This one liner is OK for
> that.
> 
> Of course it would be great if Konrad wanted to volunteer to submit a
> patch that updates d->config for all fields, or gets rid of reg->data
> entirely.
> 
> Konrad, what do you think?

You owe me a beer :-)

I will take me some time unless I can find a way to clone myself.