Re: [Qemu-devel] [PATCH] hw/pci: fixed crash when using rombar=0 for hotplugged devices

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

On Wed, 2014-10-22 at 09:18 +0300, Michael S. Tsirkin wrote:
> On Tue, Oct 21, 2014 at 03:37:12PM +0300, Marcel Apfelbaum wrote:
> > ROM images must be loaded at startup. Usage of rombar=0 after that
> > is not allowed, but should not crash QEMU.
> > 
> > Check that the device is not hotplugged before trying to
> > insert the rom file.
> > 
> > Signed-off-by: Marcel Apfelbaum <marcel.a@redhat.com>
> > ---
> >  hw/pci/pci.c | 11 ++++++++++-
> >  1 file changed, 10 insertions(+), 1 deletion(-)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index 6ce75aa..3907c90 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -1776,7 +1776,12 @@ static int pci_qdev_init(DeviceState *qdev)
> >          pci_dev->romfile = g_strdup(pc->romfile);
> >          is_default_rom = true;
> >      }
> > -    pci_add_option_rom(pci_dev, is_default_rom);
> > +
> > +    rc = pci_add_option_rom(pci_dev, is_default_rom);
> > +    if (rc != 0) {
> > +        pci_unregister_device(DEVICE(pci_dev));
> > +        return rc;
> > +    }
> >  
> >      return 0;
> >  }
> 
> Fair enough for this chunk.
> 
> > @@ -1940,6 +1945,10 @@ static int pci_add_option_rom(PCIDevice *pdev, bool is_default_rom)
> >          if (class == 0x0300) {
> >              rom_add_vga(pdev->romfile);
> >          } else {
> > +            if (DEVICE(pdev)->hotplugged) {
> > +                error_report("PCI: rombar can't be 0 for hotplugged devices!");
> > +                return -1;
> > +            }
> >              rom_add_option(pdev->romfile, -1);
> >          }
> >          return 0;
> 
> 
> The message is confusing. rombar=0 is ok if you
> don't also try to force romfile.
> Generally why are you adding this logic in pci?
Because rom_add_option will call eventually rom_insert 
that will crash QEMU with the call to hw_error.

> And what about e.g. vga?
This logic would apply also to rom_add_vga, I was not
aware we can hotplug vga devices. Can we?
I can add it also to vga, of course.

> I think the right thing to do is to propagate return codes correctly,
> and report the error where it occurs.
I can remove the error_report, but this gives an extra hint to user.
I didn't see any other way to propagate the error message. 
Should I drop it?

Thanks,
Marcel  
> 
> > -- 
> > 1.8.3.1