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SubjectRE: [PATCH v3 08/12] Drivers: hv: vmbus: Ignore the offers when resuming from hibernation
Date
From: Dexuan Cui <decui@microsoft.com>  Sent: Monday, August 19, 2019 6:52 PM
>
> When the VM resumes, the host re-sends the offers. We should not add the
> offers to the global vmbus_connection.chn_list again.
>
> This patch assumes the RELIDs of the channels don't change across
> hibernation. Actually this is not always true, especially in the case of
> NIC SR-IOV the VF vmbus device's RELID sometimes can change. A later patch
> will address this issue by mapping the new offers to the old channels and
> fixing up the old channels, if necessary.
>
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
> drivers/hv/channel_mgmt.c | 29 ++++++++++++++++++++++++++++-
> drivers/hv/connection.c | 27 +++++++++++++++++++++++++++
> drivers/hv/hyperv_vmbus.h | 3 +++
> 3 files changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
> index addcef5..f7a1184 100644
> --- a/drivers/hv/channel_mgmt.c
> +++ b/drivers/hv/channel_mgmt.c
> @@ -854,12 +854,39 @@ void vmbus_initiate_unload(bool crash)
> static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
> {
> struct vmbus_channel_offer_channel *offer;
> - struct vmbus_channel *newchannel;
> + struct vmbus_channel *oldchannel, *newchannel;
> + size_t offer_sz;
>
> offer = (struct vmbus_channel_offer_channel *)hdr;
>
> trace_vmbus_onoffer(offer);
>
> + mutex_lock(&vmbus_connection.channel_mutex);
> + oldchannel = find_primary_channel_by_offer(offer);
> + mutex_unlock(&vmbus_connection.channel_mutex);
> +
> + if (oldchannel != NULL) {
> + atomic_dec(&vmbus_connection.offer_in_progress);
> +
> + /*
> + * We're resuming from hibernation: we expect the host to send
> + * exactly the same offers that we had before the hibernation.
> + */
> + offer_sz = sizeof(*offer);
> + if (memcmp(offer, &oldchannel->offermsg, offer_sz) == 0)
> + return;
> +
> + pr_debug("Mismatched offer from the host (relid=%d)\n",
> + offer->child_relid);
> +
> + print_hex_dump_debug("Old vmbus offer: ", DUMP_PREFIX_OFFSET,
> + 16, 4, &oldchannel->offermsg, offer_sz,
> + false);
> + print_hex_dump_debug("New vmbus offer: ", DUMP_PREFIX_OFFSET,
> + 16, 4, offer, offer_sz, false);
> + return;
> + }
> +
> /* Allocate the channel object and save this offer. */
> newchannel = alloc_channel();
> if (!newchannel) {
> diff --git a/drivers/hv/connection.c b/drivers/hv/connection.c
> index 09829e1..6c7a983 100644
> --- a/drivers/hv/connection.c
> +++ b/drivers/hv/connection.c
> @@ -337,6 +337,33 @@ struct vmbus_channel *relid2channel(u32 relid)
> }
>
> /*
> + * find_primary_channel_by_offer - Get the channel object given the new offer.
> + * This is only used in the resume path of hibernation.
> + */
> +struct vmbus_channel *
> +find_primary_channel_by_offer(const struct vmbus_channel_offer_channel *offer)
> +{
> + struct vmbus_channel *channel;
> + const guid_t *inst1, *inst2;
> +
> + WARN_ON(!mutex_is_locked(&vmbus_connection.channel_mutex));
> +
> + /* Ignore sub-channel offers. */
> + if (offer->offer.sub_channel_index != 0)
> + return NULL;
> +
> + list_for_each_entry(channel, &vmbus_connection.chn_list, listentry) {
> + inst1 = &channel->offermsg.offer.if_instance;
> + inst2 = &offer->offer.if_instance;
> +
> + if (guid_equal(inst1, inst2))
> + return channel;
> + }
> +
> + return NULL;
> +}

Any particular reason this new function is in connection.c instead of
putting it in channel_mgmt.c where it is called?

> +
> +/*
> * vmbus_on_event - Process a channel event notification
> *
> * For batched channels (default) optimize host to guest signaling
> diff --git a/drivers/hv/hyperv_vmbus.h b/drivers/hv/hyperv_vmbus.h
> index 9f7fb6d..c42b46d 100644
> --- a/drivers/hv/hyperv_vmbus.h
> +++ b/drivers/hv/hyperv_vmbus.h
> @@ -310,6 +310,9 @@ int vmbus_add_channel_kobj(struct hv_device *device_obj,
>
> struct vmbus_channel *relid2channel(u32 relid);
>
> +struct vmbus_channel *
> +find_primary_channel_by_offer(const struct vmbus_channel_offer_channel *offer);
> +
> void vmbus_free_channels(void);
>
> /* Connection interface */
> --
> 1.8.3.1

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