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| author | Andrea Parri (Microsoft) <parri.andrea@gmail.com> | 2020-04-06 02:15:13 +0200 |
|---|---|---|
| committer | Wei Liu <wei.liu@kernel.org> | 2020-04-23 15:17:12 +0200 |
| commit | 7527810573436f00e582d3d5ef2eb3c027c98d7d (patch) | |
| tree | 997d4cf7717c0aa82de7649cd10f0de9fd99bb7f /drivers/hv/channel.c | |
| parent | Drivers: hv: vmbus: Synchronize init_vp_index() vs. CPU hotplug (diff) | |
| download | linux-7527810573436f00e582d3d5ef2eb3c027c98d7d.tar.xz linux-7527810573436f00e582d3d5ef2eb3c027c98d7d.zip | |
Drivers: hv: vmbus: Introduce the CHANNELMSG_MODIFYCHANNEL message type
VMBus version 4.1 and later support the CHANNELMSG_MODIFYCHANNEL(22)
message type which can be used to request Hyper-V to change the vCPU
that a channel will interrupt.
Introduce the CHANNELMSG_MODIFYCHANNEL message type, and define the
vmbus_send_modifychannel() function to send CHANNELMSG_MODIFYCHANNEL
requests to the host via a hypercall. The function is then used to
define a sysfs "store" operation, which allows to change the (v)CPU
the channel will interrupt by using the sysfs interface. The feature
can be used for load balancing or other purposes.
One interesting catch here is that Hyper-V can *not* currently ACK
CHANNELMSG_MODIFYCHANNEL messages with the promise that (after the ACK
is sent) the channel won't send any more interrupts to the "old" CPU.
The peculiarity of the CHANNELMSG_MODIFYCHANNEL messages is problematic
if the user want to take a CPU offline, since we don't want to take a
CPU offline (and, potentially, "lose" channel interrupts on such CPU)
if the host is still processing a CHANNELMSG_MODIFYCHANNEL message
associated to that CPU.
It is worth mentioning, however, that we have been unable to observe
the above mentioned "race": in all our tests, CHANNELMSG_MODIFYCHANNEL
requests appeared *as if* they were processed synchronously by the host.
Suggested-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: Andrea Parri (Microsoft) <parri.andrea@gmail.com>
Link: https://lore.kernel.org/r/20200406001514.19876-11-parri.andrea@gmail.com
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
[ wei: fix conflict in channel_mgmt.c ]
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Diffstat (limited to 'drivers/hv/channel.c')
| -rw-r--r-- | drivers/hv/channel.c | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 132e476f87b2..90070b337c10 100644 --- a/drivers/hv/channel.c +++ b/drivers/hv/channel.c @@ -290,6 +290,34 @@ int vmbus_send_tl_connect_request(const guid_t *shv_guest_servie_id, EXPORT_SYMBOL_GPL(vmbus_send_tl_connect_request); /* + * Set/change the vCPU (@target_vp) the channel (@child_relid) will interrupt. + * + * CHANNELMSG_MODIFYCHANNEL messages are aynchronous. Also, Hyper-V does not + * ACK such messages. IOW we can't know when the host will stop interrupting + * the "old" vCPU and start interrupting the "new" vCPU for the given channel. + * + * The CHANNELMSG_MODIFYCHANNEL message type is supported since VMBus version + * VERSION_WIN10_V4_1. + */ +int vmbus_send_modifychannel(u32 child_relid, u32 target_vp) +{ + struct vmbus_channel_modifychannel conn_msg; + int ret; + + memset(&conn_msg, 0, sizeof(conn_msg)); + conn_msg.header.msgtype = CHANNELMSG_MODIFYCHANNEL; + conn_msg.child_relid = child_relid; + conn_msg.target_vp = target_vp; + + ret = vmbus_post_msg(&conn_msg, sizeof(conn_msg), true); + + trace_vmbus_send_modifychannel(&conn_msg, ret); + + return ret; +} +EXPORT_SYMBOL_GPL(vmbus_send_modifychannel); + +/* * create_gpadl_header - Creates a gpadl for the specified buffer */ static int create_gpadl_header(void *kbuffer, u32 size, |