[dpdk-dev] [PATCH v3 18/19] vhost: add flag to enable postcopy live-migration
Maxime Coquelin
maxime.coquelin at redhat.com
Mon Oct 8 18:54:48 CEST 2018
On 10/08/2018 06:25 PM, Ilya Maximets wrote:
> Have you missed this mail while preparing v4?
Yes I did... Thanks for the heads-up!
Maxime
> Best regards, Ilya Maximets.
>
> On 05.10.2018 17:24, Ilya Maximets wrote:
>> I think it'll be nice to have a warning in case zero-copy
>> and postcopy enabled at the same time. This warning will
>> clarify for users why postcopy is not enabled.
>> What do you think?
>>
>> Maybe we can also move the check from the previous patch to
>> rte_vhost_driver_register() like it done for VIRTIO_F_IN_ORDER ?
>> We can't change the set of enabled features in runtime anyway.
>>
>> Best regards, Ilya Maximets.
>>
>> On 04.10.2018 11:14, Maxime Coquelin wrote:
>>> Postcopy live-migration feature require the application to
>>> not populate the guest memory. As the vhost library cannot
>>> prevent the application to that (e.g. preventing the
>>> application to call mlockall()), the feature is disabled by
>>> default.
>>>
>>> The application should only enable the feature if it does not
>>> force the guest memory to be populated.
>>>
>>> In case the user passes the RTE_VHOST_USER_POSTCOPY_SUPPORT
>>> flag at registration but the feature was not compiled,
>>> registration fails.
>>>
>>> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
>>> ---
>>> doc/guides/prog_guide/vhost_lib.rst | 8 ++++++++
>>> lib/librte_vhost/rte_vhost.h | 1 +
>>> lib/librte_vhost/socket.c | 19 +++++++++++++++++--
>>> 3 files changed, 26 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/doc/guides/prog_guide/vhost_lib.rst b/doc/guides/prog_guide/vhost_lib.rst
>>> index 77af4d775..c77df338f 100644
>>> --- a/doc/guides/prog_guide/vhost_lib.rst
>>> +++ b/doc/guides/prog_guide/vhost_lib.rst
>>> @@ -106,6 +106,14 @@ The following is an overview of some key Vhost API functions:
>>> Enabling this flag with these Qemu version results in Qemu being blocked
>>> when multiple queue pairs are declared.
>>>
>>> + - ``RTE_VHOST_USER_POSTCOPY_SUPPORT``
>>> +
>>> + Postcopy live-migration support will be enabled when this flag is set.
>>> + It is disabled by default.
>>> +
>>> + Enabling this flag should only be done when the calling application does
>>> + not pre-fault the guest shared memory, otherwise migration would fail.
>>> +
>>> * ``rte_vhost_driver_set_features(path, features)``
>>>
>>> This function sets the feature bits the vhost-user driver supports. The
>>> diff --git a/lib/librte_vhost/rte_vhost.h b/lib/librte_vhost/rte_vhost.h
>>> index b3cc6990d..b26afbffa 100644
>>> --- a/lib/librte_vhost/rte_vhost.h
>>> +++ b/lib/librte_vhost/rte_vhost.h
>>> @@ -28,6 +28,7 @@ extern "C" {
>>> #define RTE_VHOST_USER_NO_RECONNECT (1ULL << 1)
>>> #define RTE_VHOST_USER_DEQUEUE_ZERO_COPY (1ULL << 2)
>>> #define RTE_VHOST_USER_IOMMU_SUPPORT (1ULL << 3)
>>> +#define RTE_VHOST_USER_POSTCOPY_SUPPORT (1ULL << 4)
>>>
>>> /** Protocol features. */
>>> #ifndef VHOST_USER_PROTOCOL_F_MQ
>>> diff --git a/lib/librte_vhost/socket.c b/lib/librte_vhost/socket.c
>>> index c04d3d305..3df303be8 100644
>>> --- a/lib/librte_vhost/socket.c
>>> +++ b/lib/librte_vhost/socket.c
>>> @@ -51,6 +51,8 @@ struct vhost_user_socket {
>>> uint64_t supported_features;
>>> uint64_t features;
>>>
>>> + uint64_t protocol_features;
>>> +
>>> /*
>>> * Device id to identify a specific backend device.
>>> * It's set to -1 for the default software implementation.
>>> @@ -731,7 +733,7 @@ rte_vhost_driver_get_protocol_features(const char *path,
>>> did = vsocket->vdpa_dev_id;
>>> vdpa_dev = rte_vdpa_get_device(did);
>>> if (!vdpa_dev || !vdpa_dev->ops->get_protocol_features) {
>>> - *protocol_features = VHOST_USER_PROTOCOL_FEATURES;
>>> + *protocol_features = vsocket->protocol_features;
>>> goto unlock_exit;
>>> }
>>>
>>> @@ -744,7 +746,7 @@ rte_vhost_driver_get_protocol_features(const char *path,
>>> goto unlock_exit;
>>> }
>>>
>>> - *protocol_features = VHOST_USER_PROTOCOL_FEATURES
>>> + *protocol_features = vsocket->protocol_features
>>> & vdpa_protocol_features;
>>>
>>> unlock_exit:
>>> @@ -863,6 +865,7 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
>>> vsocket->use_builtin_virtio_net = true;
>>> vsocket->supported_features = VIRTIO_NET_SUPPORTED_FEATURES;
>>> vsocket->features = VIRTIO_NET_SUPPORTED_FEATURES;
>>> + vsocket->protocol_features = VHOST_USER_PROTOCOL_FEATURES;
>>>
>>> /* Dequeue zero copy can't assure descriptors returned in order */
>>> if (vsocket->dequeue_zero_copy) {
>>> @@ -875,6 +878,18 @@ rte_vhost_driver_register(const char *path, uint64_t flags)
>>> vsocket->features &= ~(1ULL << VIRTIO_F_IOMMU_PLATFORM);
>>> }
>>>
>>> + if (!(flags & RTE_VHOST_USER_POSTCOPY_SUPPORT)) {
>>> + vsocket->protocol_features &=
>>> + ~(1ULL << VHOST_USER_PROTOCOL_F_PAGEFAULT);
>>> + } else {
>>> +#ifndef RTE_LIBRTE_VHOST_POSTCOPY
>>> + RTE_LOG(ERR, VHOST_CONFIG,
>>> + "Postcopy requested but not compiled\n");
>>> + ret = -1;
>>> + goto out_mutex;
>>> +#endif
>>> + }
>>> +
>>> if ((flags & RTE_VHOST_USER_CLIENT) != 0) {
>>> vsocket->reconnect = !(flags & RTE_VHOST_USER_NO_RECONNECT);
>>> if (vsocket->reconnect && reconn_tid == 0) {
>>>
>>
>>
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