Re: [Xen-devel][PATCH 1/3] VT-d: support Intel IGD passthrough

[Weidong Han <weidong.han@xxxxxxxxx>]

Ian Jackson wrote:
> Han, Weidong writes ("[Xen-devel][PATCH 1/3] VT-d: support Intel IGD passthrough 
> "):
>   
> > Some registers of Intel IGD are mapped in host bridge, so it needs
> > to passthrough these registers of physical host bridge to guest
> > because emulated host bridge in guest doesn't have these mappings.
> >
> > Some VBIOSs and drivers ssume the IGD BDF (bus:device:function) is
> > always 00:02.0, so this patch reserves 00:02.0 for assigned IGD in
> > guest.
> >     
> Thanks for the contribution, which I have applied with a very small
> change to avoid having an open else at #endif.
>
> However the part in pci.c is really very ugly indeed.  If we ever get
> around to rebasing to recent upstream qemu and trying to upstream our
> patches, this is sure to be dropped.  So you might profitably spend
> some time thinking how to make it less ugly.
>
> Thanks,
> Ian.
>   
Thanks for check-in.  I agree the hacking in pci.c is not elegant. We 
will think how to make it cleaner.
Regards,
Weidong


>   
> > +#ifdef CONFIG_PASSTHROUGH
> > +    /* host bridge reads for IGD passthrough */
> > +    if ( igd_passthru && pci_dev->devfn == 0x00 )
> > +    {
> > +        val = pci_dev->config_read(pci_dev, config_addr, len);
> > +
> > +        if ( config_addr == 0x00 && len == 4 )
> > +            val = pt_pci_host_read_long(0, 0, 0, 0x00);
> > +        else if ( config_addr == 0x02 ) // Device ID
> > +            val = pt_pci_host_read_word(0, 0, 0, 0x02);
> > +        else if ( config_addr == 0x52 ) // GMCH Graphics Control Register
> > +            val = pt_pci_host_read_word(0, 0, 0, 0x52);
> > +        else if ( config_addr == 0xa0 ) // GMCH Top of Memory Register
> > +            val = pt_pci_host_read_word(0, 0, 0, 0xa0);
> > +    }
> > +    else if ( igd_passthru && pci_dev->devfn == 0x10 &&
> > +              config_addr == 0xfc ) // read on IGD device
> > +        val = 0;  // use SMI to communicate with the system BIOS
> > +    else
> > +#endif
> > +        val = pci_dev->config_read(pci_dev, config_addr, len);
> > +
> >     

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