Re: [PATCH RFC v2] vPCI: account for hidden devices

[Jan Beulich <jbeulich@xxxxxxxx>]

On 24.05.2023 17:56, Roger Pau Monné wrote:
> On Wed, May 24, 2023 at 03:45:58PM +0200, Jan Beulich wrote:
>> --- a/xen/drivers/vpci/header.c
>> +++ b/xen/drivers/vpci/header.c
>> @@ -218,6 +218,7 @@ static int modify_bars(const struct pci_
>>      struct vpci_header *header = &pdev->vpci->header;
>>      struct rangeset *mem = rangeset_new(NULL, NULL, 0);
>>      struct pci_dev *tmp, *dev = NULL;
>> +    const struct domain *d;
>>      const struct vpci_msix *msix = pdev->vpci->msix;
>>      unsigned int i;
>>      int rc;
>> @@ -285,9 +286,11 @@ static int modify_bars(const struct pci_
>>  
>>      /*
>>       * Check for overlaps with other BARs. Note that only BARs that are
>> -     * currently mapped (enabled) are checked for overlaps.
>> +     * currently mapped (enabled) are checked for overlaps. Note also that
>> +     * for Dom0 we also need to include hidden, i.e. DomXEN's, devices.
>>       */
>> -    for_each_pdev ( pdev->domain, tmp )
>> +for ( d = pdev->domain; ; d = dom_xen ) {//todo
> 
> Looking at this again, I think this is slightly more complex, as during
> runtime dom0 will get here with pdev->domain == hardware_domain OR
> dom_xen, and hence you also need to account that devices that have
> pdev->domain == dom_xen need to iterate over devices that belong to
> the hardware_domain, ie:
> 
> for ( d = pdev->domain; ;
>       d = (pdev->domain == dom_xen) ? hardware_domain : dom_xen )

Right, something along these lines. To keep loop continuation expression
and exit condition simple, I'll probably prefer

for ( d = pdev->domain != dom_xen ? pdev->domain : hardware_domain;
      ; d = dom_xen )

> And we likely want to limit this to devices that belong to the
> hardware_domain or to dom_xen (in preparation for vPCI being used for
> domUs).

I'm afraid I don't understand this remark, though.

Jan