Re: [PATCH dpdk v2] vfio/ppc64/spapr: Warn if DMA window was created at unexpected offset

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

> From: dev [mailto:dev-bounces@dpdk.org] On Behalf Of Alexey
> Kardashevskiy
> Sent: Wednesday, April 26, 2017 9:09 AM
> To: dev@dpdk.org
> Cc: Alexey Kardashevskiy <aik@ozlabs.ru>
> Subject: [dpdk-dev] [PATCH dpdk v2] vfio/ppc64/spapr: Warn if DMA
> window was created at unexpected offset
> 
> VFIO_IOMMU_SPAPR_TCE_CREATE ioctl() returns the actual bus address for
> just created DMA window. It happens to start from zero because the default
> window is removed (leaving no windows) and new window starts from zero.
> However this is not guaranteed and a new window may start from another
> address, this adds a check and an error message.
> 
> 
> Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
> ---
> Changes:
> v2:
> * this just prints warning and fails instead of incorrectly changing IOVA
> addresses
> ---
>  lib/librte_eal/linuxapp/eal/eal_vfio.c | 8 +++++++-
>  1 file changed, 7 insertions(+), 1 deletion(-)
> 
> diff --git a/lib/librte_eal/linuxapp/eal/eal_vfio.c
> b/lib/librte_eal/linuxapp/eal/eal_vfio.c
> index 46f951f4d..530815790 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_vfio.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_vfio.c
> @@ -702,6 +702,13 @@ vfio_spapr_dma_map(int vfio_container_fd)
>  		return -1;
>  	}
> 
> +	if (create.start_addr) {
> +		RTE_LOG(ERR, EAL,
> +			"  DMA offsets other than zero is not supported, "
> +			"new window is created at %lx\n",
> create.start_addr);
> +		return -1;
> +	}
> +
>  	/* map all DPDK segments for DMA. use 1:1 PA to IOVA mapping */
>  	for (i = 0; i < RTE_MAX_MEMSEG; i++) {
>  		struct vfio_iommu_type1_dma_map dma_map; @@ -734,7
> +741,6 @@ vfio_spapr_dma_map(int vfio_container_fd)
>  				"error %i (%s)\n", errno, strerror(errno));
>  			return -1;
>  		}
> -
>  	}
> 
>  	return 0;
> --
> 2.11.0

Hi Alexey,

There are some compile failures with this patch. You'll probably want to replace %lx with PRIx64 or similar :)

I would argue that just saying "DMA offsets other than zero are not supported" will be sufficient and will make error message less confusing. Up to you though.

Thanks,
Anatoly