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

[Michael S. Tsirkin]

On Wed, Oct 22, 2014 at 10:34:21AM +0300, Marcel Apfelbaum wrote:
> 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 <address@hidden>
> > > ---
> > >  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.

So fix rom_insert to return an error code instead?

> > 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.

Move it to rom_insert, instead of hw_error.

> I didn't see any other way to propagate the error message. 
> Should I drop it?
> 
> Thanks,
> Marcel  
> > 
> > > -- 
> > > 1.8.3.1
> 
>