Re: [PATCH RESEND] pci: Disallow improper BAR registration for type 1

[Ben Widawsky <ben.widawsky@intel.com>]

On 20-10-14 13:52:29, Michael S. Tsirkin wrote:
> On Wed, Oct 14, 2020 at 10:18:53AM -0700, Ben Widawsky wrote:
> > This patch informs future developers working on root complexes, root
> > ports, or bridges that also wish to implement a BAR for those. PCI type
> > 1 headers only support 2 base address registers. It is incorrect and
> > difficult to figure out what is wrong with the device when this mistake
> > is made. With this, it is immediate and obvious what has gone wrong.
> > 
> > Signed-off-by: Ben Widawsky <ben.widawsky@intel.com>
> 
> How about an assert + a comment?
> This is how we usually handle developer bugs. error_report is
> for user errors and similar issues ...

Sure, I can do that. I was copying the error above mine which should probably
also be changed to an assert then, yes?

I can submit that as well with v2 of this if you'd like.

> 
> > ---
> >  hw/pci/pci.c | 10 ++++++++++
> >  1 file changed, 10 insertions(+)
> > 
> > diff --git a/hw/pci/pci.c b/hw/pci/pci.c
> > index 3c8f10b461..55b0302c57 100644
> > --- a/hw/pci/pci.c
> > +++ b/hw/pci/pci.c
> > @@ -1141,6 +1141,7 @@ void pci_register_bar(PCIDevice *pci_dev, int region_num,
> >      uint32_t addr; /* offset in pci config space */
> >      uint64_t wmask;
> >      pcibus_t size = memory_region_size(memory);
> > +    uint8_t hdr_type;
> >  
> >      assert(region_num >= 0);
> >      assert(region_num < PCI_NUM_REGIONS);
> > @@ -1150,6 +1151,15 @@ void pci_register_bar(PCIDevice *pci_dev, int region_num,
> >          exit(1);
> >      }
> >  
> > +    hdr_type =
> > +        pci_dev->config[PCI_HEADER_TYPE] & ~PCI_HEADER_TYPE_MULTI_FUNCTION;
> > +    if (hdr_type == PCI_HEADER_TYPE_BRIDGE && region_num > 1) {
> > +        error_report("ERROR: PCI Type 1 header only has 2 BARs "
> > +                     "requested BAR=%d",
> > +                     region_num);
> > +        exit(1);
> > +    }
> > +
> >      r = &pci_dev->io_regions[region_num];
> >      r->addr = PCI_BAR_UNMAPPED;
> >      r->size = size;
> > -- 
> > 2.28.0
>