Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Ilya Maximets]

------- Original Message -------
Sender : Flavio Leitner<fbl@sysclose.org>
Date : Apr 06, 2016 07:14 (GMT+03:00)
Title : Re: [RFC] vhost-user public struct refactor (was Re: [dpdk-dev] [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

On Tue, Apr 05, 2016 at 01:47:33PM +0800, Yuanhan Liu wrote:
> On Fri, Feb 19, 2016 at 03:06:50PM +0800, Yuanhan Liu wrote:
> > On Fri, Feb 19, 2016 at 09:32:41AM +0300, Ilya Maximets wrote:
> > > Array of buf_vector's is just an array for temporary storing information
> > > about available descriptors. It used only locally in virtio_dev_merge_rx()
> > > and there is no reason for that array to be shared.
> > > 
> > > Fix that by allocating local buf_vec inside virtio_dev_merge_rx().
> > > 
> > > Signed-off-by: Ilya Maximets 
> > > ---
> > >  lib/librte_vhost/rte_virtio_net.h |  1 -
> > >  lib/librte_vhost/vhost_rxtx.c     | 45 ++++++++++++++++++++-------------------
> > >  2 files changed, 23 insertions(+), 23 deletions(-)
> > > 
> > > diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
> > > index 10dcb90..ae1e4fb 100644
> > > --- a/lib/librte_vhost/rte_virtio_net.h
> > > +++ b/lib/librte_vhost/rte_virtio_net.h
> > > @@ -91,7 +91,6 @@ struct vhost_virtqueue {
> > >   int kickfd; /**< Currently unused as polling mode is enabled. */
> > >   int enabled;
> > >   uint64_t reserved[16]; /**< Reserve some spaces for future extension. */
> > > - struct buf_vector buf_vec[BUF_VECTOR_MAX]; /**< for scatter RX. */
> > >  } __rte_cache_aligned;
> > 
> > I like this kind of cleanup, however, it breaks ABI.
> 
> So, I was considering to add vhost-user Tx delayed-copy (or zero copy)
> support recently, which comes to yet another ABI violation, as we need
> add a new field to virtio_memory_regions struct to do guest phys addr
> to host phys addr translation. You may ask, however, that why do we need
> expose virtio_memory_regions struct to users at all?
> 
> You are right, we don't have to. And here is the thing: we exposed way
> too many fields (or even structures) than necessary. Say, vhost_virtqueue
> struct should NOT be exposed to user at all: application just need to
> tell the right queue id to locate a specific queue, and that's all.
> The structure should be defined in an internal header file. With that,
> we could do any changes to it we want, without worrying about that we
> may offense the painful ABI rules.
> 
> Similar changes could be done to virtio_net struct as well, just exposing
> very few fields that are necessary and moving all others to an internal
> structure.
> 
> Huawei then suggested a more radical yet much cleaner one: just exposing
> a virtio_net handle to application, just like the way kernel exposes an
> fd to user for locating a specific file. However, it's more than an ABI
> change; it's also an API change: some fields are referenced by applications,
> such as flags, virt_qp_nb. We could expose some new functions to access
> them though.
> 
> I'd vote for this one, as it sounds very clean to me. This would also
> solve the block issue of this patch. Though it would break OVS, I'm thinking
> that'd be okay, as OVS has dependence on DPDK version: what we need to
> do is just to send few patches to OVS, and let it points to next release,
> say DPDK v16.07. Flavio, please correct me if I'm wrong.

> There is a plan to use vHost PMD, so from OVS point of view the virtio
> stuff would be hidden because vhost PMD would look like just as a
> regular ethernet, right?

But we still need to have access to virtqueue_enabe/disable notifications to
work properly. How this will be done if virtqueue will be hidden from user?

Best regards, Ilya Maximets.

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Yuanhan Liu]

On Wed, Apr 06, 2016 at 05:11:01AM +0000, Ilya Maximets wrote:
> > There is a plan to use vHost PMD, so from OVS point of view the virtio
> > stuff would be hidden because vhost PMD would look like just as a
> > regular ethernet, right?
> 
> But we still need to have access to virtqueue_enabe/disable notifications to
> work properly. How this will be done if virtqueue will be hidden from user?

Do you mean vring_state_changed() callback? It will not be removed.
BTW, when using vhost pmd, you will not be aware of such callback:
it will be translated to a RTE_ETH_EVENT_QUEUE_STATE interrupt.

OTOH, I have a simple git grep of "vq" from ovs dpdk netdev code,
it returns nothing. So, I don't think that will matter?

	--yliu

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Ilya Maximets]

------- Original Message -------
Sender : Yuanhan Liu<yuanhan.liu@linux.intel.com>
Date : Apr 06, 2016 08:38 (GMT+03:00)
Title : Re: Re: [RFC] vhost-user public struct refactor (was Re: [dpdk-dev] [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

On Wed, Apr 06, 2016 at 05:11:01AM +0000, Ilya Maximets wrote:
> > > There is a plan to use vHost PMD, so from OVS point of view the virtio
> > > stuff would be hidden because vhost PMD would look like just as a
> > > regular ethernet, right?
> > 
> > But we still need to have access to virtqueue_enabe/disable notifications to
> > work properly. How this will be done if virtqueue will be hidden from user?
>
> Do you mean vring_state_changed() callback? It will not be removed.
> BTW, when using vhost pmd, you will not be aware of such callback:
> it will be translated to a RTE_ETH_EVENT_QUEUE_STATE interrupt.
>
> OTOH, I have a simple git grep of "vq" from ovs dpdk netdev code,
> it returns nothing. So, I don't think that will matter?

OK, thanks for clarifying.
I guess, all should be fine in that case. Thank you.

Best regards, Ilya Maximets.

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Yuanhan Liu]

On Wed, Apr 06, 2016 at 01:14:09AM -0300, Flavio Leitner wrote:
> > 
> > I'd vote for this one, as it sounds very clean to me. This would also
> > solve the block issue of this patch. Though it would break OVS, I'm thinking
> > that'd be okay, as OVS has dependence on DPDK version: what we need to
> > do is just to send few patches to OVS, and let it points to next release,
> > say DPDK v16.07. Flavio, please correct me if I'm wrong.
> 
> There is a plan to use vHost PMD,

Great.

> so from OVS point of view the virtio
> stuff would be hidden because vhost PMD would look like just as a
> regular ethernet, right?

Yes.

	--yliu

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Flavio Leitner]

On Tue, Apr 05, 2016 at 01:47:33PM +0800, Yuanhan Liu wrote:
> On Fri, Feb 19, 2016 at 03:06:50PM +0800, Yuanhan Liu wrote:
> > On Fri, Feb 19, 2016 at 09:32:41AM +0300, Ilya Maximets wrote:
> > > Array of buf_vector's is just an array for temporary storing information
> > > about available descriptors. It used only locally in virtio_dev_merge_rx()
> > > and there is no reason for that array to be shared.
> > > 
> > > Fix that by allocating local buf_vec inside virtio_dev_merge_rx().
> > > 
> > > Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
> > > ---
> > >  lib/librte_vhost/rte_virtio_net.h |  1 -
> > >  lib/librte_vhost/vhost_rxtx.c     | 45 ++++++++++++++++++++-------------------
> > >  2 files changed, 23 insertions(+), 23 deletions(-)
> > > 
> > > diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
> > > index 10dcb90..ae1e4fb 100644
> > > --- a/lib/librte_vhost/rte_virtio_net.h
> > > +++ b/lib/librte_vhost/rte_virtio_net.h
> > > @@ -91,7 +91,6 @@ struct vhost_virtqueue {
> > >  	int			kickfd;			/**< Currently unused as polling mode is enabled. */
> > >  	int			enabled;
> > >  	uint64_t		reserved[16];		/**< Reserve some spaces for future extension. */
> > > -	struct buf_vector	buf_vec[BUF_VECTOR_MAX];	/**< for scatter RX. */
> > >  } __rte_cache_aligned;
> > 
> > I like this kind of cleanup, however, it breaks ABI.
> 
> So, I was considering to add vhost-user Tx delayed-copy (or zero copy)
> support recently, which comes to yet another ABI violation, as we need
> add a new field to virtio_memory_regions struct to do guest phys addr
> to host phys addr translation. You may ask, however, that why do we need
> expose virtio_memory_regions struct to users at all?
> 
> You are right, we don't have to. And here is the thing: we exposed way
> too many fields (or even structures) than necessary. Say, vhost_virtqueue
> struct should NOT be exposed to user at all: application just need to
> tell the right queue id to locate a specific queue, and that's all.
> The structure should be defined in an internal header file. With that,
> we could do any changes to it we want, without worrying about that we
> may offense the painful ABI rules.
> 
> Similar changes could be done to virtio_net struct as well, just exposing
> very few fields that are necessary and moving all others to an internal
> structure.
> 
> Huawei then suggested a more radical yet much cleaner one: just exposing
> a virtio_net handle to application, just like the way kernel exposes an
> fd to user for locating a specific file. However, it's more than an ABI
> change; it's also an API change: some fields are referenced by applications,
> such as flags, virt_qp_nb. We could expose some new functions to access
> them though.
> 
> I'd vote for this one, as it sounds very clean to me. This would also
> solve the block issue of this patch. Though it would break OVS, I'm thinking
> that'd be okay, as OVS has dependence on DPDK version: what we need to
> do is just to send few patches to OVS, and let it points to next release,
> say DPDK v16.07. Flavio, please correct me if I'm wrong.

There is a plan to use vHost PMD, so from OVS point of view the virtio
stuff would be hidden because vhost PMD would look like just as a
regular ethernet, right?

I think we are waiting for 16.04 to be released with that so we can
start push changes to OVS as well.

-- 
fbl

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Yuanhan Liu]

On Tue, Apr 05, 2016 at 10:37:13AM +0200, Thomas Monjalon wrote:
> 2016-04-05 13:47, Yuanhan Liu:
> > So, I was considering to add vhost-user Tx delayed-copy (or zero copy)
> > support recently, which comes to yet another ABI violation, as we need
> > add a new field to virtio_memory_regions struct to do guest phys addr
> > to host phys addr translation. You may ask, however, that why do we need
> > expose virtio_memory_regions struct to users at all?
> > 
> > You are right, we don't have to. And here is the thing: we exposed way
> > too many fields (or even structures) than necessary. Say, vhost_virtqueue
> > struct should NOT be exposed to user at all: application just need to
> > tell the right queue id to locate a specific queue, and that's all.
> > The structure should be defined in an internal header file. With that,
> > we could do any changes to it we want, without worrying about that we
> > may offense the painful ABI rules.
> > 
> > Similar changes could be done to virtio_net struct as well, just exposing
> > very few fields that are necessary and moving all others to an internal
> > structure.
> > 
> > Huawei then suggested a more radical yet much cleaner one: just exposing
> > a virtio_net handle to application, just like the way kernel exposes an
> > fd to user for locating a specific file. However, it's more than an ABI
> > change; it's also an API change: some fields are referenced by applications,
> > such as flags, virt_qp_nb. We could expose some new functions to access
> > them though.
> > 
> > I'd vote for this one, as it sounds very clean to me. This would also
> > solve the block issue of this patch. Though it would break OVS, I'm thinking
> > that'd be okay, as OVS has dependence on DPDK version: what we need to
> > do is just to send few patches to OVS, and let it points to next release,
> > say DPDK v16.07. Flavio, please correct me if I'm wrong.
> > 
> > Thoughts/comments?
> 
> Do you plan to send a deprecation notice to change API in 16.07?

Yes, I planned to, shortly. Before that, I'd ask for comments first.

	--yliu

Re: [dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Thomas Monjalon]

2016-04-05 13:47, Yuanhan Liu:
> So, I was considering to add vhost-user Tx delayed-copy (or zero copy)
> support recently, which comes to yet another ABI violation, as we need
> add a new field to virtio_memory_regions struct to do guest phys addr
> to host phys addr translation. You may ask, however, that why do we need
> expose virtio_memory_regions struct to users at all?
> 
> You are right, we don't have to. And here is the thing: we exposed way
> too many fields (or even structures) than necessary. Say, vhost_virtqueue
> struct should NOT be exposed to user at all: application just need to
> tell the right queue id to locate a specific queue, and that's all.
> The structure should be defined in an internal header file. With that,
> we could do any changes to it we want, without worrying about that we
> may offense the painful ABI rules.
> 
> Similar changes could be done to virtio_net struct as well, just exposing
> very few fields that are necessary and moving all others to an internal
> structure.
> 
> Huawei then suggested a more radical yet much cleaner one: just exposing
> a virtio_net handle to application, just like the way kernel exposes an
> fd to user for locating a specific file. However, it's more than an ABI
> change; it's also an API change: some fields are referenced by applications,
> such as flags, virt_qp_nb. We could expose some new functions to access
> them though.
> 
> I'd vote for this one, as it sounds very clean to me. This would also
> solve the block issue of this patch. Though it would break OVS, I'm thinking
> that'd be okay, as OVS has dependence on DPDK version: what we need to
> do is just to send few patches to OVS, and let it points to next release,
> say DPDK v16.07. Flavio, please correct me if I'm wrong.
> 
> Thoughts/comments?

Do you plan to send a deprecation notice to change API in 16.07?

[dpdk-dev] [RFC] vhost-user public struct refactor (was Re: [PATCH RFC 2/4] vhost: make buf vector for scatter RX) local.

[Yuanhan Liu]

On Fri, Feb 19, 2016 at 03:06:50PM +0800, Yuanhan Liu wrote:
> On Fri, Feb 19, 2016 at 09:32:41AM +0300, Ilya Maximets wrote:
> > Array of buf_vector's is just an array for temporary storing information
> > about available descriptors. It used only locally in virtio_dev_merge_rx()
> > and there is no reason for that array to be shared.
> > 
> > Fix that by allocating local buf_vec inside virtio_dev_merge_rx().
> > 
> > Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
> > ---
> >  lib/librte_vhost/rte_virtio_net.h |  1 -
> >  lib/librte_vhost/vhost_rxtx.c     | 45 ++++++++++++++++++++-------------------
> >  2 files changed, 23 insertions(+), 23 deletions(-)
> > 
> > diff --git a/lib/librte_vhost/rte_virtio_net.h b/lib/librte_vhost/rte_virtio_net.h
> > index 10dcb90..ae1e4fb 100644
> > --- a/lib/librte_vhost/rte_virtio_net.h
> > +++ b/lib/librte_vhost/rte_virtio_net.h
> > @@ -91,7 +91,6 @@ struct vhost_virtqueue {
> >  	int			kickfd;			/**< Currently unused as polling mode is enabled. */
> >  	int			enabled;
> >  	uint64_t		reserved[16];		/**< Reserve some spaces for future extension. */
> > -	struct buf_vector	buf_vec[BUF_VECTOR_MAX];	/**< for scatter RX. */
> >  } __rte_cache_aligned;
> 
> I like this kind of cleanup, however, it breaks ABI.

So, I was considering to add vhost-user Tx delayed-copy (or zero copy)
support recently, which comes to yet another ABI violation, as we need
add a new field to virtio_memory_regions struct to do guest phys addr
to host phys addr translation. You may ask, however, that why do we need
expose virtio_memory_regions struct to users at all?

You are right, we don't have to. And here is the thing: we exposed way
too many fields (or even structures) than necessary. Say, vhost_virtqueue
struct should NOT be exposed to user at all: application just need to
tell the right queue id to locate a specific queue, and that's all.
The structure should be defined in an internal header file. With that,
we could do any changes to it we want, without worrying about that we
may offense the painful ABI rules.

Similar changes could be done to virtio_net struct as well, just exposing
very few fields that are necessary and moving all others to an internal
structure.

Huawei then suggested a more radical yet much cleaner one: just exposing
a virtio_net handle to application, just like the way kernel exposes an
fd to user for locating a specific file. However, it's more than an ABI
change; it's also an API change: some fields are referenced by applications,
such as flags, virt_qp_nb. We could expose some new functions to access
them though.

I'd vote for this one, as it sounds very clean to me. This would also
solve the block issue of this patch. Though it would break OVS, I'm thinking
that'd be okay, as OVS has dependence on DPDK version: what we need to
do is just to send few patches to OVS, and let it points to next release,
say DPDK v16.07. Flavio, please correct me if I'm wrong.

Thoughts/comments?

	--yliu