lkml.org 
[lkml]   [2020]   [Apr]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
From
SubjectRE: [PATCH 10/11] Drivers: hv: vmbus: Introduce the CHANNELMSG_MODIFYCHANNEL message type
Date
From: Andrea Parri (Microsoft) <parri.andrea@gmail.com> Sent: Sunday, April 5, 2020 5:15 PM
>
> 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>
> ---
> drivers/hv/channel.c | 28 ++++++++++
> drivers/hv/channel_mgmt.c | 2 +-
> drivers/hv/hv_trace.h | 19 +++++++
> drivers/hv/vmbus_drv.c | 108 +++++++++++++++++++++++++++++++++++++-
> include/linux/hyperv.h | 10 +++-
> 5 files changed, 163 insertions(+), 4 deletions(-)
>

Reviewed-by: Michael Kelley <mikelley@microsoft.com>

\
 
 \ /
  Last update: 2020-04-10 21:35    [W:0.070 / U:8.204 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site