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

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

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>, 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.

~Andrew