Re: [Qemu-devel] [PATCH v4 2/2] hw/pci: fixed hotplug crash when using rombar=0 with devices having romfile

[Marcel Apfelbaum <marcel.a@redhat.com>]

On Mon, 2014-11-03 at 14:40 +0100, Markus Armbruster wrote:
> Marcel Apfelbaum <marcel.a@redhat.com> writes:
> 
> > On Mon, 2014-11-03 at 13:03 +0100, Markus Armbruster wrote:
> >> Marcel Apfelbaum <marcel.a@redhat.com> writes:
> >> 
> >> > Hot-plugging a device that has a romfile (either supplied by user
> >> > or built-in) using rombar=0 option is a user error,
> >> > do not allow the device to be hot-plugged.
> >> >
> >> > Reviewed-by: Eric Blake <eblake@redhat.com>
> >> > Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> >> > ---
> >> >  hw/pci/pci.c | 9 +++++++++
> >> >  1 file changed, 9 insertions(+)
> >> >
> >> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> >> > index 36226eb..371699c 100644
> >> > --- a/hw/pci/pci.c
> >> > +++ b/hw/pci/pci.c
> >> > @@ -1942,6 +1942,15 @@ static int pci_add_option_rom(PCIDevice *pdev, bool is_default_rom)
> >> >           * for 0.11 compatibility.
> >> >           */
> >> >          int class = pci_get_word(pdev->config + PCI_CLASS_DEVICE);
> >> > +
> >> > +        /*
> >> > +         * Hot-plugged devices can't use the option ROM
> >> > +         * if the rom bar is disabled.
> >> > +         */
> >> > +        if (DEVICE(pdev)->hotplugged) {
> >> > +            return -1;
> >> > +        }
> >> > +
> >> >          if (class == 0x0300) {
> >> >              rom_add_vga(pdev->romfile);
> >> >          } else {
> >> 
> >> Unlike the function's other unsuccessful returns, this one is silent.
> >> Intentional?
> > Yes, the first version included an error message, but was not accepted
> > as the reviewers preferred "silent drop" instead.
> > The main reason was that a proper error propagation mechanism
> > should be used.
> > At the time of the patch there was not such an option, but now there is.
> > I can add it on top of your series, preferably after is merged.
> 
> My rebased "pci: Convert core to realize" has this hunk:
> 
>     @@ -1948,7 +1955,9 @@ static int pci_add_option_rom(PCIDevice *pdev, bool is_default_rom)
>               * if the rom bar is disabled.
>               */
>              if (DEVICE(pdev)->hotplugged) {
>     -            return -1;
>     +            error_setg(errp, "Hot-plugged device without ROM bar"
>     +                       " can't have an option ROM");
>     +            return;
>              }
> 
>              if (class == 0x0300) {
> 
> Bad, because the patch does two separate things: fix a failure not to be
> silent, and convert to realize.  Needs to be split.  Begs the question
> how to order the parts.  I'd prefer to put the fix first, and get it
> into 2.2.  What do you think?

If I understand your question correctly:
I would first convert to realize, then add the fix.
The reason for it is pretty simple: Conversion to realize
gives us the error flow propagation we need.

Thanks,
Marcel