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

["Philippe Mathieu-Daudé" <philmd@redhat.com>]

On 10/14/20 7:56 PM, Ben Widawsky wrote:
> 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.

Yes, and please don't start with "This patch ...":

https://wiki.qemu.org/Contribute/SubmitAPatch#Write_a_meaningful_commit_message

> 
>>
>>> ---
>>>   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
>>
>