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

[Markus Armbruster]

Stefano Stabellini <address@hidden> writes:

> 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?

Can do.  Best for all the xen-only PCI devices, not just this one.

I'd prefer to do it on top of a conversion to realize.  Makes the task
depend on [PATCH 00/10] pci: Partial conversion to realize.