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

[Michael S. Tsirkin]

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 ...

> ---
>  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