Re: [PATCH 2/2] VT-d: have set_msi_source_id() return a success indicator

[Jan Beulich <jbeulich@xxxxxxxx>]

On 13.03.2025 16:01, Andrew Cooper wrote:
> On 13/03/2025 1:34 pm, Jan Beulich wrote:
>> Handling possible internal errors by just emitting a (debug-build-only)
>> log message can't be quite enough. Return error codes in those cases,
>> and have the caller propagate those up.
>>
>> Drop a pointless return path, rather than "inventing" an error code for
>> it.
>>
>> While touching the function declarator anyway also constify its first
>> parameter.
>>
>> Fixes: 476bbccc811c ("VT-d: fix MSI source-id of interrupt remapping")
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>,

Thanks.

> although...
> 
>> --- a/xen/drivers/passthrough/vtd/intremap.c
>> +++ b/xen/drivers/passthrough/vtd/intremap.c
>> @@ -436,15 +436,13 @@ void cf_check io_apic_write_remap_rte(
>>      __ioapic_write_entry(apic, pin, true, old_rte);
>>  }
>>  
>> -static void set_msi_source_id(struct pci_dev *pdev, struct iremap_entry 
>> *ire)
>> +static int set_msi_source_id(const struct pci_dev *pdev,
>> +                             struct iremap_entry *ire)
>>  {
>>      u16 seg;
>>      u8 bus, devfn, secbus;
>>      int ret;
>>  
>> -    if ( !pdev || !ire )
>> -        return;
>> -
>>      seg = pdev->seg;
>>      bus = pdev->bus;
>>      devfn = pdev->devfn;
>> @@ -485,16 +483,21 @@ static void set_msi_source_id(struct pci
>>                              PCI_BDF(bus, devfn));
>>          }
>>          else
>> +        {
>>              dprintk(XENLOG_WARNING VTDPREFIX,
>>                      "d%d: no upstream bridge for %pp\n",
>>                      pdev->domain->domain_id, &pdev->sbdf);
> 
> as you're doing cleanup, %pd here?  Given DOM_IO for quarantine, I think
> it's more likely now than it used to be.
> 
>> +            return -ENXIO;
>> +        }
>>          break;
>>  
>>      default:
>>          dprintk(XENLOG_WARNING VTDPREFIX, "d%d: unknown(%u): %pp\n",
>>                  pdev->domain->domain_id, pdev->type, &pdev->sbdf);
> 
> Here too.  Also, the "unknown(%u)" is less than ideal.  "%pd: %pp
> unknown type %u\n" would be better.

To be honest this feels like going too far with unrelated cleanup here,
even if it's all in patch context. It would be different if at least I
touched those dprintk() invocations.

Jan