Re: [Qemu-devel] -device xen-platform crashes

[Stefano Stabellini]

On Fri, 30 Jan 2015, Markus Armbruster wrote:
> Stefano Stabellini <address@hidden> writes:
> 
> > On Thu, 29 Jan 2015, Markus Armbruster wrote:
> >> Stefano Stabellini <address@hidden> writes:
> >> 
> >> > On Thu, 29 Jan 2015, Markus Armbruster wrote:
> >> >> Reproducer: qemu -nodefaults -S -display none -device xen-platform
> >> >> 
> >> >> Yes, xen-platform makes no sense without Xen, but it shouldn't crash.
> >> >
> >> > Is it just a matter of doing the following?
> >> >
> >> > diff --git a/hw/i386/xen/xen_platform.c b/hw/i386/xen/xen_platform.c
> >> > index 28b324a..40ae1f3 100644
> >> > --- a/hw/i386/xen/xen_platform.c
> >> > +++ b/hw/i386/xen/xen_platform.c
> >> > @@ -177,6 +177,10 @@ static void platform_fixed_ioport_writeb(void 
> >> > *opaque, uint32_t addr, uint32_t v
> >> >  {
> >> >      PCIXenPlatformState *s = opaque;
> >> >  
> >> > +    if (!xen_enabled()) {
> >> > +        return;
> >> > +    }
> >> > +
> >> >      switch (addr) {
> >> >      case 0: /* Platform flags */ {
> >> >          hvmmem_type_t mem_type = (val & PFFLAG_ROM_LOCK) ?
> >> 
> >> Fixes the crash for me.
> >> 
> >> Should Xen-only devices fail to realize when !xen_enabled()?
> >  
> > Accelerators are configured after device registration unfortunately.
> 
> Realization happens even later, doesn't it?

Yes, you are right.


> With this patch:
> 
>     @@ -389,6 +393,11 @@ static int xen_platform_initfn(PCIDevice *dev)
>          PCIXenPlatformState *d = XEN_PLATFORM(dev);
>          uint8_t *pci_conf;
> 
>     +    if (!xen_enabled()) {
>     +        error_report("Nope");
>     +        return -1;
>     +    }
>     +
>          pci_conf = dev->config;
> 
>          pci_set_word(pci_conf + PCI_COMMAND, PCI_COMMAND_IO | 
> PCI_COMMAND_MEMORY);
> 
> I get:
> 
>     $ upstream-qemu -nodefaults -S -display none -device xen-platform
>     upstream-qemu: -device xen-platform: Nope
>     upstream-qemu: -device xen-platform: Device initialization failed.
>     upstream-qemu: -device xen-platform: Device 'xen-platform' could not be 
> initialized
>     [Exit 1 ]
> 
> Note that error_report() is a bit problematic in init methods.  The best
> solution is to convert the device to realize (requires my "pci: Partial
> conversion to realize" series) and use error_setg().

I agree that this is much better than breaking at runtime for no clear
reason. Are you going to submit a proper patch?