Re: [Xen-devel] [PATCH v2 08/30] xen/x86: do the PCI scan unconditionally

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 27.09.16 at 17:57, <roger.pau@xxxxxxxxxx> wrote:
> Instead of being tied to the presence of an IOMMU

At the very least I'd expect the "why" aspect to get mentioned
here.

> --- a/xen/drivers/passthrough/amd/pci_amd_iommu.c
> +++ b/xen/drivers/passthrough/amd/pci_amd_iommu.c
> @@ -219,7 +219,8 @@ int __init amd_iov_detect(void)
>  
>      if ( !amd_iommu_perdev_intremap )
>          printk(XENLOG_WARNING "AMD-Vi: Using global interrupt remap table is 
> not recommended (see XSA-36)!\n");
> -    return scan_pci_devices();
> +
> +    return 0;
>  }

Not how an error return from the function at least here does not
get ignored, leading to the IOMMU not getting enabled. This behavior
should be preserved, and I think it actually should extend to VT-d.
Furthermore iiuc you make PVHv2 Dom0 setup depend on this
succeeding, which may then require further propagation of the
success status here (or maybe, just like PVHv1, you require a
functional IOMMU, in which case failing IOMMU setup would be
sufficient).

Jan


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