Re: [Qemu-devel] [PATCH v2 2/2] vhost-user: back SET/GET_CONFIG requests with a protocol feature

[Liu, Changpeng]

> -----Original Message-----
> From: Maxime Coquelin [mailto:address@hidden
> Sent: Thursday, March 29, 2018 3:56 PM
> To: Liu, Changpeng <address@hidden>; address@hidden;
> address@hidden; address@hidden
> Subject: Re: [PATCH v2 2/2] vhost-user: back SET/GET_CONFIG requests with a
> protocol feature
> 
> 
> 
> On 03/29/2018 02:57 AM, Liu, Changpeng wrote:
> >
> >
> >> -----Original Message-----
> >> From: Maxime Coquelin [mailto:address@hidden
> >> Sent: Thursday, March 29, 2018 3:28 AM
> >> To: address@hidden; Liu, Changpeng <address@hidden>;
> >> address@hidden; address@hidden
> >> Cc: Maxime Coquelin <address@hidden>
> >> Subject: [PATCH v2 2/2] vhost-user: back SET/GET_CONFIG requests with a
> >> protocol feature
> >>
> >> Without a dedicated protocol feature, QEMU cannot know whether
> >> the backend can handle VHOST_USER_SET_CONFIG and
> >> VHOST_USER_GET_CONFIG messages.
> >>
> >> This patch adds a protocol feature that is only advertised by
> >> QEMU if the device implements the config ops. Vhost user init
> >> fails if the device support the feature but the backend doesn't.
> >>
> >> The backend should only send VHOST_USER_SLAVE_CONFIG_CHANGE_MSG
> >> requests if the protocol feature has been negotiated.
> >>
> >> Signed-off-by: Maxime Coquelin <address@hidden>
> >
> > Passed our own vhost-user-blk target with the patch, I can submit a fix to
> QEMU vhost-user-blk example
> > after this commit.
> >
> > Tested-by: Changpeng Liu <address@hidden>
> 
> Thanks for having tested, and for proposing to implement the example
> part. Just notice I forgot to apply your Tested-by on the series.
I have added the fix to the example based on your patch, I'm wondering
I can send it out for review now or wait for your commit being merged ?
> 
> Maxime
> >> ---
> >>   docs/interop/vhost-user.txt | 21 ++++++++++++---------
> >>   hw/virtio/vhost-user.c      | 22 ++++++++++++++++++++++
> >>   2 files changed, 34 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/docs/interop/vhost-user.txt b/docs/interop/vhost-user.txt
> >> index c058c407df..534caab18a 100644
> >> --- a/docs/interop/vhost-user.txt
> >> +++ b/docs/interop/vhost-user.txt
> >> @@ -379,6 +379,7 @@ Protocol features
> >>   #define VHOST_USER_PROTOCOL_F_CROSS_ENDIAN   6
> >>   #define VHOST_USER_PROTOCOL_F_CRYPTO_SESSION 7
> >>   #define VHOST_USER_PROTOCOL_F_PAGEFAULT      8
> >> +#define VHOST_USER_PROTOCOL_F_CONFIG         9
> >>
> >>   Master message types
> >>   --------------------
> >> @@ -664,7 +665,8 @@ Master message types
> >>         Master payload: virtio device config space
> >>         Slave payload: virtio device config space
> >>
> >> -      Submitted by the vhost-user master to fetch the contents of the 
> >> virtio
> >> +      When VHOST_USER_PROTOCOL_F_CONFIG is negotiated, this message is
> >> +      submitted by the vhost-user master to fetch the contents of the 
> >> virtio
> >>         device configuration space, vhost-user slave's payload size MUST 
> >> match
> >>         master's request, vhost-user slave uses zero length of payload to
> >>         indicate an error to vhost-user master. The vhost-user master may
> >> @@ -677,7 +679,8 @@ Master message types
> >>         Master payload: virtio device config space
> >>         Slave payload: N/A
> >>
> >> -      Submitted by the vhost-user master when the Guest changes the virtio
> >> +      When VHOST_USER_PROTOCOL_F_CONFIG is negotiated, this message is
> >> +      submitted by the vhost-user master when the Guest changes the virtio
> >>         device configuration space and also can be used for live migration
> >>         on the destination host. The vhost-user slave must check the flags
> >>         field, and slaves MUST NOT accept SET_CONFIG for read-only
> >> @@ -766,13 +769,13 @@ Slave message types
> >>        Slave payload: N/A
> >>        Master payload: N/A
> >>
> >> -     Vhost-user slave sends such messages to notify that the virtio 
> >> device's
> >> -     configuration space has changed, for those host devices which can
> support
> >> -     such feature, host driver can send VHOST_USER_GET_CONFIG message to
> >> slave
> >> -     to get the latest content. If VHOST_USER_PROTOCOL_F_REPLY_ACK is
> >> -     negotiated, and slave set the VHOST_USER_NEED_REPLY flag, master must
> >> -     respond with zero when operation is successfully completed, or 
> >> non-zero
> >> -     otherwise.
> >> +     When VHOST_USER_PROTOCOL_F_CONFIG is negotiated, vhost-user slave
> >> sends
> >> +     such messages to notify that the virtio device's configuration space 
> >> has
> >> +     changed, for those host devices which can support such feature, host
> >> +     driver can send VHOST_USER_GET_CONFIG message to slave to get the
> latest
> >> +     content. If VHOST_USER_PROTOCOL_F_REPLY_ACK is negotiated, and
> slave
> >> set
> >> +     the VHOST_USER_NEED_REPLY flag, master must respond with zero when
> >> +     operation is successfully completed, or non-zero otherwise.
> >>
> >>   VHOST_USER_PROTOCOL_F_REPLY_ACK:
> >>   -------------------------------
> >> diff --git a/hw/virtio/vhost-user.c b/hw/virtio/vhost-user.c
> >> index 44aea5c0a8..cc8a24aa31 100644
> >> --- a/hw/virtio/vhost-user.c
> >> +++ b/hw/virtio/vhost-user.c
> >> @@ -46,6 +46,7 @@ enum VhostUserProtocolFeature {
> >>       VHOST_USER_PROTOCOL_F_CROSS_ENDIAN = 6,
> >>       VHOST_USER_PROTOCOL_F_CRYPTO_SESSION = 7,
> >>       VHOST_USER_PROTOCOL_F_PAGEFAULT = 8,
> >> +    VHOST_USER_PROTOCOL_F_CONFIG = 9,
> >>       VHOST_USER_PROTOCOL_F_MAX
> >>   };
> >>
> >> @@ -1211,6 +1212,17 @@ static int vhost_user_init(struct vhost_dev *dev,
> void
> >> *opaque)
> >>
> >>           dev->protocol_features =
> >>               protocol_features & VHOST_USER_PROTOCOL_FEATURE_MASK;
> >> +
> >> +        if (!dev->config_ops || 
> >> !dev->config_ops->vhost_dev_config_notifier) {
> >> +            /* Dont acknowledge CONFIG feature if device doesn't support 
> >> it */
> >> +            dev->protocol_features &= ~(1ULL <<
> >> VHOST_USER_PROTOCOL_F_CONFIG);
> >> +        } else if (!(protocol_features &
> >> +                    (1ULL << VHOST_USER_PROTOCOL_F_CONFIG))) {
> >> +            error_report("Device expects VHOST_USER_PROTOCOL_F_CONFIG "
> >> +                    "but backend does not support it.");
> >> +            return -1;
> >> +        }
> >> +
> >>           err = vhost_user_set_protocol_features(dev, 
> >> dev->protocol_features);
> >>           if (err < 0) {
> >>               return err;
> >> @@ -1405,6 +1417,11 @@ static int vhost_user_get_config(struct vhost_dev
> >> *dev, uint8_t *config,
> >>           .hdr.size = VHOST_USER_CONFIG_HDR_SIZE + config_len,
> >>       };
> >>
> >> +    if (!virtio_has_feature(dev->protocol_features,
> >> +                VHOST_USER_PROTOCOL_F_CONFIG)) {
> >> +        return -1;
> >> +    }
> >> +
> >>       if (config_len > VHOST_USER_MAX_CONFIG_SIZE) {
> >>           return -1;
> >>       }
> >> @@ -1448,6 +1465,11 @@ static int vhost_user_set_config(struct vhost_dev
> >> *dev, const uint8_t *data,
> >>           .hdr.size = VHOST_USER_CONFIG_HDR_SIZE + size,
> >>       };
> >>
> >> +    if (!virtio_has_feature(dev->protocol_features,
> >> +                VHOST_USER_PROTOCOL_F_CONFIG)) {
> >> +        return -1;
> >> +    }
> >> +
> >>       if (reply_supported) {
> >>           msg.hdr.flags |= VHOST_USER_NEED_REPLY_MASK;
> >>       }
> >> --
> >> 2.14.3
> >