Re: [dpdk-dev] [PATCH v2] examples/vhost_crypto: fix zero copy

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 11/14/18 12:16 PM, Fan Zhang wrote:
> This patch fixes the zero copy enable problem for vhost crypto
> sample application.
> 
> For some Crypto PMDs such as AESNI-MB and AESNI-GCM the data to
> be processed will be made a copy in the same buffer but next to the
> data. For example, to encrypt 64 bytes data the PMD will copy this
> data from offset 64 to offset 123. This requires the application
> provides the buffer with at least double of the data size.
> 
> However there is no way for VMs to know this limitation. When
> zero-copy is enabled in Vhost the PMD may overwrite the buffer
> next to the VM data to be processed, and further cause problems
> such as Segmentation Fault or even worse, crashes the VM.
> 
> To fix the problem the user should avoid enabling the zero copy
> for these Crypto PMDs. This patch adds the checking of the PMD
> names to see if zero copy can be applied.
> 
> Fixes: 709521f4c2cd ("examples/vhost_crypto: support multi-core")
> 
> Signed-off-by: Fan Zhang <roy.fan.zhang@intel.com>
> ---
> v2:
> - removed unecessary checks
> - Changed log message when zero-copy is not applicable.
> 
>   examples/vhost_crypto/main.c | 17 +++++++++++++++++
>   1 file changed, 17 insertions(+)
> 

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks!
Maxime