Re: [dpdk-dev] [dpdk-stable] [PATCH v4 2/5] bus/pci: use IOVAs check when setting IOVA mode

["Eelco Chaudron" <echaudro@redhat.com>]

On 10 Jul 2018, at 19:25, Alejandro Lucero wrote:

> Although VT-d emulation currently only supports 39 bits, it could
> be iovas being within that supported range. This patch allows
> IOVA mode in such a case.
>
> Indeed, memory initialization code can be modified for using lower
> virtual addresses than those used by the kernel for 64 bits processes
> by default, and therefore memsegs iovas can use 39 bits or less for
> most system. And this is likely 100% true for VMs.
>
> Applicable to v17.11.3 only.
>
> Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
> ---
>  drivers/bus/pci/linux/pci.c | 15 +++++++++++----
>  1 file changed, 11 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/bus/pci/linux/pci.c b/drivers/bus/pci/linux/pci.c
> index 74deef3..792c819 100644
> --- a/drivers/bus/pci/linux/pci.c
> +++ b/drivers/bus/pci/linux/pci.c
> @@ -43,6 +43,7 @@
>  #include <rte_devargs.h>
>  #include <rte_memcpy.h>
>  #include <rte_vfio.h>
> +#include <rte_memory.h>
>
>  #include "eal_private.h"
>  #include "eal_filesystem.h"
> @@ -613,10 +614,12 @@
>  	fclose(fp);
>
>  	mgaw = ((vtd_cap_reg & VTD_CAP_MGAW_MASK) >> VTD_CAP_MGAW_SHIFT) + 
> 1;
> -	if (mgaw < X86_VA_WIDTH)
> +
> +	if (!rte_eal_check_dma_mask(mgaw))
> +		return true;
> +	else
>  		return false;
>
> -	return true;
>  }
>  #elif defined(RTE_ARCH_PPC_64)
>  static bool
> @@ -640,13 +643,17 @@
>  {
>  	struct rte_pci_device *dev = NULL;
>  	struct rte_pci_driver *drv = NULL;
> +	int iommu_dma_mask_check_done = 0;
>
>  	FOREACH_DRIVER_ON_PCIBUS(drv) {
>  		FOREACH_DEVICE_ON_PCIBUS(dev) {
>  			if (!rte_pci_match(drv, dev))
>  				continue;
> -			if (!pci_one_device_iommu_support_va(dev))
> -				return false;
> +			if (!iommu_dma_mask_check_done) {
> +				if (pci_one_device_iommu_support_va(dev) < 0)
> +					return false;
> +				iommu_dma_mask_check_done  = 1;

As I do not know enough on what IOMMU hardware can coexist, I leave this 
patch for others to review.
Here is the previous question/answer:

>>> Not sure why this change? Why do we only need to check one device on 
>>> all the buses?

>> Because there is just one emulated IOMMU hardware. The limitation in 
>> this case is not in a specific PCI device. And I do not think it is 
>> possible to have two different (emulated or not) IOMMU hardware. Yes, 
>> you can have more than one controller but being same IOMMU type.

If the above is confirmed, you can consider this patch ack’ed.

> +			}
>  		}
>  	}
>  	return true;
> -- 
> 1.9.1