[dpdk-dev] [PATCH v2 2/4] eal: fix IOVA mode selection as VA for pci drivers

[Burakov, Anatoly]

On 16-Jul-19 2:46 PM, jerinj at marvell.com wrote:
> From: David Marchand <david.marchand at redhat.com>
> 
> The incriminated commit broke the use of RTE_PCI_DRV_IOVA_AS_VA which
> was intended to mean "driver only supports VA" but had been understood
> as "driver supports both PA and VA" by most net drivers and used to let
> dpdk processes to run as non root (which do not have access to physical
> addresses on recent kernels).
> 
> The check on physical addresses actually closed the gap for those
> drivers. We don't need to mark them with RTE_PCI_DRV_IOVA_AS_VA and this
> flag can retain its intended meaning.
> Document explicitly its meaning.
> 
> We can check that a driver requirement wrt to IOVA mode is fulfilled
> before trying to probe a device.
> 
> Finally, document the heuristic used to select the IOVA mode and hope
> that we won't break it again.
> 
> Fixes: 703458e19c16 ("bus/pci: consider only usable devices for IOVA mode")
> 
> Signed-off-by: David Marchand <david.marchand at redhat.com>
> Reviewed-by: Jerin Jacob <jerinj at marvell.com>
> Tested-by: Jerin Jacob <jerinj at marvell.com>
> ---

<snip>

> @@ -629,12 +643,16 @@ rte_pci_get_iommu_class(void)
>   				devices_want_va = true;
>   		}
>   	}
> -	if (devices_want_pa) {
> -		iova_mode = RTE_IOVA_PA;
> -		if (devices_want_va)
> -			RTE_LOG(WARNING, EAL, "Some devices want 'VA' but forcing 'PA' because other devices want it\n");
> -	} else if (devices_want_va) {
> +	if (devices_want_va && !devices_want_pa) {
>   		iova_mode = RTE_IOVA_VA;
> +	} else if (devices_want_pa && !devices_want_va) {
> +		iova_mode = RTE_IOVA_PA;
> +	} else {
> +		iova_mode = RTE_IOVA_DC;
> +		if (devices_want_va) {
> +			RTE_LOG(WARNING, EAL, "Some devices want 'VA' but forcing 'DC' because other devices want 'PA'.\n");
> +			RTE_LOG(WARNING, EAL, "Depending on the final decision by the EAL, part of your devices won't initialise.\n");

Tiny nitpick - i generally don't like personal appeals in log messages, 
so perhaps drop the "your"? I.e. "Depending on final decision by EAL, 
not all devices may be able to initialize."? Same applies to the other 
instance of this error message.

Otherwise, LGTM

Acked-by: Anatoly Burakov <anatoly.burakov at intel.com>

-- 
Thanks,
Anatoly