Re: [PATCH kvm-unit-tests v5 09/14] pci: provide pci_scan_bars()

[Peter Xu <peterx@redhat.com>]

On Wed, Nov 16, 2016 at 10:50:37AM +0100, Alexander Gordeev wrote:

[...]

> >  struct pci_dev {
> >  	uint16_t bdf;
> > +	phys_addr_t bar[PCI_BAR_NUM];
> 
> This questions pop up time and again. If bars are 32 or 64 bit?
> What if bar is not 64 aligned? etc.

Could you help elaborate what does "not 64 aligned" mean here? AFAIU
the bar can only be either 32bit or 64bit wide?

> 
> I guess, it worth mentionig in comment that bar[] array here does
> not match PCI header binary layout.

Not sure whether you mean this:

    void pci_scan_bars(struct pci_dev *dev)
    {
        int i, cur = 0;

        for (i = 0; i < PCI_BAR_NUM; i++) {
            if (!pci_bar_is_valid(dev, i))
                continue;
            dev->bar[cur++] = pci_bar_get_addr(dev, i);
            if (pci_bar_is64(dev, i))
                i++;
        }
    }

Assume that we have a device with:

- bar 0: 32 bit addr A0
- bar 1: 64 bit addr A1
- bar 2: 32 bit addr A2

The original patch will generate:

  dev->bar[0] == A0
  dev->bar[1] == A1
  dev->bar[2] == 0
  dev->bar[3] == A2
  dev->bar[4] == 0
  dev->bar[5] == 0

The new code (above) will generate:

  dev->bar[0] == A0
  dev->bar[1] == A1
  dev->bar[2] == A2
  dev->bar[3] == 0
  dev->bar[4] == 0
  dev->bar[5] == 0

Thanks,

-- peterx