[dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc

[dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc

[Wenzhuo Lu]

The description of i40e 16 bytes descriptor is not clear
enough. Add more details.

Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
---
 doc/guides/nics/i40e.rst | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
index a0946e6..e0237a8 100644
--- a/doc/guides/nics/i40e.rst
+++ b/doc/guides/nics/i40e.rst
@@ -398,13 +398,20 @@ used to classify MPLS packet by using a command in testpmd like:
    testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
             0x8847 fwd queue <M>
 
-16 Byte Descriptor cannot be used on DPDK VF
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+16 Bytes Descriptor setting on DPDK VF
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+Until 2.1.26, the Linux i40e driver doesn't support 16 bytes RX descriptor.
 If the Linux i40e kernel driver is used as host driver, while DPDK i40e PMD
 is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. That
 is to say, user should keep ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in
 config file.
+In the future, if the Linux i40e driver supports 16 bytes RX descriptor, user
+should make sure the DPDK VF uses the same RX descriptor mode, 16 bytes or 32
+bytes, as the PF driver.
+
+The same rule for DPDK PF + DPDK VF. The PF and VF should use the same RX
+descriptor mode. Or the VF RX will not work.
 
 Receive packets with Ethertype 0x88A8
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 
1.9.3

Re: [dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc

[Bruce Richardson]

On Wed, Oct 25, 2017 at 10:54:53AM +0800, Wenzhuo Lu wrote:
> The description of i40e 16 bytes descriptor is not clear
> enough. Add more details.
> 
> Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> ---

Good idea to document this better.

>  doc/guides/nics/i40e.rst | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
> index a0946e6..e0237a8 100644
> --- a/doc/guides/nics/i40e.rst
> +++ b/doc/guides/nics/i40e.rst
> @@ -398,13 +398,20 @@ used to classify MPLS packet by using a command in testpmd like:
>     testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
>              0x8847 fwd queue <M>
>  
> -16 Byte Descriptor cannot be used on DPDK VF
> -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +16 Bytes Descriptor setting on DPDK VF
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>  
> +Until 2.1.26, the Linux i40e driver doesn't support 16 bytes RX descriptor.

I assume that 2.1.26 is referring to the i40e driver version, not the
linux kernel version. This should be made clearer, as it also could be
read as a very old kernel version.

>  If the Linux i40e kernel driver is used as host driver, while DPDK i40e PMD
>  is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. That
>  is to say, user should keep ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in
>  config file.

Can you explain - either on-list here, or actually in the docs - why
there is this restriction? Is it HW or SW? A reference to the section in
the datasheet for it would also be good. For example Table 8-10 in the
datasheet lists no restriction on the Dsize bit in the queue context.

> +In the future, if the Linux i40e driver supports 16 bytes RX descriptor, user
> +should make sure the DPDK VF uses the same RX descriptor mode, 16 bytes or 32
> +bytes, as the PF driver.
> +
> +The same rule for DPDK PF + DPDK VF. The PF and VF should use the same RX
> +descriptor mode. Or the VF RX will not work.
>  
>  Receive packets with Ethertype 0x88A8
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> -- 
> 1.9.3
> 


Regards,
/Bruce

Re: [dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc

[Lu, Wenzhuo]

Hi Bruce,

> -----Original Message-----
> From: Richardson, Bruce
> Sent: Wednesday, October 25, 2017 4:37 PM
> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH] doc: more clarification for i40e 16 bytes desc
> 
> On Wed, Oct 25, 2017 at 10:54:53AM +0800, Wenzhuo Lu wrote:
> > The description of i40e 16 bytes descriptor is not clear enough. Add
> > more details.
> >
> > Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> > ---
> 
> Good idea to document this better.
> 
> >  doc/guides/nics/i40e.rst | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst index
> > a0946e6..e0237a8 100644
> > --- a/doc/guides/nics/i40e.rst
> > +++ b/doc/guides/nics/i40e.rst
> > @@ -398,13 +398,20 @@ used to classify MPLS packet by using a command
> in testpmd like:
> >     testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
> >              0x8847 fwd queue <M>
> >
> > -16 Byte Descriptor cannot be used on DPDK VF
> > -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +16 Bytes Descriptor setting on DPDK VF
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > +Until 2.1.26, the Linux i40e driver doesn't support 16 bytes RX descriptor.
> 
> I assume that 2.1.26 is referring to the i40e driver version, not the linux
> kernel version. This should be made clearer, as it also could be read as a very
> old kernel version.
OK, I'll change it to i40e 2.1.26.

> 
> >  If the Linux i40e kernel driver is used as host driver, while DPDK
> > i40e PMD  is used as the VF driver, DPDK cannot choose 16 byte receive
> > descriptor. That  is to say, user should keep
> > ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in  config file.
> 
> Can you explain - either on-list here, or actually in the docs - why there is
> this restriction? Is it HW or SW? A reference to the section in the datasheet
> for it would also be good. For example Table 8-10 in the datasheet lists no
> restriction on the Dsize bit in the queue context.
It's not a HW limitation. To my opinion, it's SW design and implementation limitation.
I'll add more details.

> 
> > +In the future, if the Linux i40e driver supports 16 bytes RX
> > +descriptor, user should make sure the DPDK VF uses the same RX
> > +descriptor mode, 16 bytes or 32 bytes, as the PF driver.
> > +
> > +The same rule for DPDK PF + DPDK VF. The PF and VF should use the
> > +same RX descriptor mode. Or the VF RX will not work.
> >
> >  Receive packets with Ethertype 0x88A8
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > --
> > 1.9.3
> >
> 
> 
> Regards,
> /Bruce

[dpdk-dev] [PATCH v2] doc: more clarification for i40e 16 bytes desc

[Wenzhuo Lu]

The description of i40e 16 bytes descriptor is not clear
enough. Add more details.

Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
---
 doc/guides/nics/i40e.rst | 21 ++++++++++++++++-----
 1 file changed, 16 insertions(+), 5 deletions(-)

diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
index a0946e6..771620c 100644
--- a/doc/guides/nics/i40e.rst
+++ b/doc/guides/nics/i40e.rst
@@ -398,13 +398,24 @@ used to classify MPLS packet by using a command in testpmd like:
    testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
             0x8847 fwd queue <M>
 
-16 Byte Descriptor cannot be used on DPDK VF
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+16 Bytes Descriptor setting on DPDK VF
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
+Currently the VF's RX descriptor mode is decided by PF. There's no PF-VF
+interface for VF to request the RX descriptor mode, also no interface to nofify
+VF its own RX descriptor mode.
+Until i40e 2.1.26, the Linux i40e driver doesn't support 16 bytes RX descriptor.
 If the Linux i40e kernel driver is used as host driver, while DPDK i40e PMD
-is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. That
-is to say, user should keep ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in
-config file.
+is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. The
+reason is that the RX descriptor is already set to 32 bytes by the i40e kernel
+driver. That is to say, user should keep
+``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in config file.
+In the future, if the Linux i40e driver supports 16 bytes RX descriptor, user
+should make sure the DPDK VF uses the same RX descriptor mode, 16 bytes or 32
+bytes, as the PF driver.
+
+The same rule for DPDK PF + DPDK VF. The PF and VF should use the same RX
+descriptor mode. Or the VF RX will not work.
 
 Receive packets with Ethertype 0x88A8
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 
1.9.3

Re: [dpdk-dev] [PATCH v2] doc: more clarification for i40e 16 bytes desc

[Bruce Richardson]

On Tue, Oct 31, 2017 at 11:40:33AM +0800, Wenzhuo Lu wrote:
> The description of i40e 16 bytes descriptor is not clear
> enough. Add more details.
> 
> Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>

Thanks for the clarification, it's better now. Couple of minor tweaks I
would suggest below.

Otherwise:
Acked-by: Bruce Richardson <bruce.richardson@intel.com>

> ---
>  doc/guides/nics/i40e.rst | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
> 
> diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
> index a0946e6..771620c 100644
> --- a/doc/guides/nics/i40e.rst
> +++ b/doc/guides/nics/i40e.rst
> @@ -398,13 +398,24 @@ used to classify MPLS packet by using a command in testpmd like:
>     testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
>              0x8847 fwd queue <M>
>  
> -16 Byte Descriptor cannot be used on DPDK VF
> -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> +16 Bytes Descriptor setting on DPDK VF
> +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We tend to refer to these as "16-byte" and "32-byte" descriptors in the
singular, not "16-bytes".

>  
> +Currently the VF's RX descriptor mode is decided by PF. There's no PF-VF
> +interface for VF to request the RX descriptor mode, also no interface to nofify
> +VF its own RX descriptor mode.
> +Until i40e 2.1.26, the Linux i40e driver doesn't support 16 bytes RX descriptor.

This implies that the 2.1.26 driver does support setting the descriptor
size, though later text implies that this is not the case.
Therefore, I suggest changing "Until i40e 2.1.26", to "For all available
versions of the i40e driver," and omit the version number, since it will
soon be out of date otherwise. The only time we should need to update
this is when/if there is a kernel version that does support reporting or
seting the descriptor size.

>  If the Linux i40e kernel driver is used as host driver, while DPDK i40e PMD
> -is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. That
> -is to say, user should keep ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in
> -config file.
> +is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. The
> +reason is that the RX descriptor is already set to 32 bytes by the i40e kernel
> +driver. That is to say, user should keep
> +``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in config file.
> +In the future, if the Linux i40e driver supports 16 bytes RX descriptor, user
> +should make sure the DPDK VF uses the same RX descriptor mode, 16 bytes or 32
> +bytes, as the PF driver.
> +
> +The same rule for DPDK PF + DPDK VF. The PF and VF should use the same RX
> +descriptor mode. Or the VF RX will not work.
>  
>  Receive packets with Ethertype 0x88A8
>  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> -- 
> 1.9.3
> 

Re: [dpdk-dev] [PATCH v2] doc: more clarification for i40e 16 bytes desc

[Lu, Wenzhuo]

Hi Bruce,


> -----Original Message-----
> From: Richardson, Bruce
> Sent: Tuesday, October 31, 2017 6:04 PM
> To: Lu, Wenzhuo <wenzhuo.lu@intel.com>
> Cc: dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2] doc: more clarification for i40e 16 bytes
> desc
> 
> On Tue, Oct 31, 2017 at 11:40:33AM +0800, Wenzhuo Lu wrote:
> > The description of i40e 16 bytes descriptor is not clear enough. Add
> > more details.
> >
> > Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
> 
> Thanks for the clarification, it's better now. Couple of minor tweaks I would
> suggest below.
> 
> Otherwise:
> Acked-by: Bruce Richardson <bruce.richardson@intel.com>
> 
> > ---
> >  doc/guides/nics/i40e.rst | 21 ++++++++++++++++-----
> >  1 file changed, 16 insertions(+), 5 deletions(-)
> >
> > diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst index
> > a0946e6..771620c 100644
> > --- a/doc/guides/nics/i40e.rst
> > +++ b/doc/guides/nics/i40e.rst
> > @@ -398,13 +398,24 @@ used to classify MPLS packet by using a command
> in testpmd like:
> >     testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
> >              0x8847 fwd queue <M>
> >
> > -16 Byte Descriptor cannot be used on DPDK VF
> > -~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > +16 Bytes Descriptor setting on DPDK VF
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> We tend to refer to these as "16-byte" and "32-byte" descriptors in the
> singular, not "16-bytes".
> 
> >
> > +Currently the VF's RX descriptor mode is decided by PF. There's no
> > +PF-VF interface for VF to request the RX descriptor mode, also no
> > +interface to nofify VF its own RX descriptor mode.
> > +Until i40e 2.1.26, the Linux i40e driver doesn't support 16 bytes RX
> descriptor.
> 
> This implies that the 2.1.26 driver does support setting the descriptor size,
> though later text implies that this is not the case.
> Therefore, I suggest changing "Until i40e 2.1.26", to "For all available
> versions of the i40e driver," and omit the version number, since it will soon
> be out of date otherwise. The only time we should need to update this is
> when/if there is a kernel version that does support reporting or seting the
> descriptor size.
Thanks for the review and comments. I'll send a V3 and add your ack :)

> 
> >  If the Linux i40e kernel driver is used as host driver, while DPDK
> > i40e PMD -is used as the VF driver, DPDK cannot choose 16 byte receive
> > descriptor. That -is to say, user should keep
> > ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in -config file.
> > +is used as the VF driver, DPDK cannot choose 16 byte receive
> > +descriptor. The reason is that the RX descriptor is already set to 32
> > +bytes by the i40e kernel driver. That is to say, user should keep
> > +``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in config file.
> > +In the future, if the Linux i40e driver supports 16 bytes RX
> > +descriptor, user should make sure the DPDK VF uses the same RX
> > +descriptor mode, 16 bytes or 32 bytes, as the PF driver.
> > +
> > +The same rule for DPDK PF + DPDK VF. The PF and VF should use the
> > +same RX descriptor mode. Or the VF RX will not work.
> >
> >  Receive packets with Ethertype 0x88A8
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > --
> > 1.9.3
> >

[dpdk-dev] [PATCH v3] doc: more clarification for i40e 16 byte desc

[Wenzhuo Lu]

The description of i40e 16 byte descriptor is not clear
enough. Add more details.

Signed-off-by: Wenzhuo Lu <wenzhuo.lu@intel.com>
Acked-by: Bruce Richardson <bruce.richardson@intel.com>
---
 doc/guides/nics/i40e.rst | 23 +++++++++++++++++------
 1 file changed, 17 insertions(+), 6 deletions(-)

diff --git a/doc/guides/nics/i40e.rst b/doc/guides/nics/i40e.rst
index a0946e6..05c1875 100644
--- a/doc/guides/nics/i40e.rst
+++ b/doc/guides/nics/i40e.rst
@@ -398,13 +398,24 @@ used to classify MPLS packet by using a command in testpmd like:
    testpmd> ethertype_filter 0 add mac_ignr 00:00:00:00:00:00 ethertype \
             0x8847 fwd queue <M>
 
-16 Byte Descriptor cannot be used on DPDK VF
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+16 Byte RX Descriptor setting on DPDK VF
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 
-If the Linux i40e kernel driver is used as host driver, while DPDK i40e PMD
-is used as the VF driver, DPDK cannot choose 16 byte receive descriptor. That
-is to say, user should keep ``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in
-config file.
+Currently the VF's RX descriptor mode is decided by PF. There's no PF-VF
+interface for VF to request the RX descriptor mode, also no interface to notify
+VF its own RX descriptor mode.
+For all available versions of the i40e driver, these drivers don't support 16
+byte RX descriptor. If the Linux i40e kernel driver is used as host driver,
+while DPDK i40e PMD is used as the VF driver, DPDK cannot choose 16 byte receive
+descriptor. The reason is that the RX descriptor is already set to 32 byte by
+the i40e kernel driver. That is to say, user should keep
+``CONFIG_RTE_LIBRTE_I40E_16BYTE_RX_DESC=n`` in config file.
+In the future, if the Linux i40e driver supports 16 byte RX descriptor, user
+should make sure the DPDK VF uses the same RX descriptor mode, 16 byte or 32
+byte, as the PF driver.
+
+The same rule for DPDK PF + DPDK VF. The PF and VF should use the same RX
+descriptor mode. Or the VF RX will not work.
 
 Receive packets with Ethertype 0x88A8
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-- 
1.9.3