ich777/linux_media
1
0
Fork 0
mirror of https://github.com/tbsdtv/linux_media.git synced 2025-07-23 20:51:03 +02:00
Code Issues Packages Projects Releases Wiki Activity

Drivers: hv: vmbus: Add comments on ring buffer signaling

Browse Source 
Add comments describing intricacies of Hyper-V ring buffer
signaling code.  This information is not in Hyper-V public
documents, so include here to capture the knowledge for
future coders.

There are no code changes in this commit.

Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Michael Kelley
2018-06-05 13:37:51 -07:00
committed by Greg Kroah-Hartman
parent e9a7fda29a
commit 71b38245ac
2 changed files with 77 additions and 19 deletions
Download Patch File Download Diff File Expand all files Collapse all files

31
include/linux/hyperv.h
View File

@@ -89,18 +89,33 @@ struct hv_ring_buffer {
u32 interrupt_mask;
/*
* Win8 uses some of the reserved bits to implement
* interrupt driven flow management. On the send side
* we can request that the receiver interrupt the sender
* when the ring transitions from being full to being able
* to handle a message of size "pending_send_sz".
* WS2012/Win8 and later versions of Hyper-V implement interrupt
* driven flow management. The feature bit feat_pending_send_sz
* is set by the host on the host->guest ring buffer, and by the
* guest on the guest->host ring buffer.
*
* Add necessary state for this enhancement.
* The meaning of the feature bit is a bit complex in that it has
* semantics that apply to both ring buffers. If the guest sets
* the feature bit in the guest->host ring buffer, the guest is
* telling the host that:
* 1) It will set the pending_send_sz field in the guest->host ring
* buffer when it is waiting for space to become available, and
* 2) It will read the pending_send_sz field in the host->guest
* ring buffer and interrupt the host when it frees enough space
*
* Similarly, if the host sets the feature bit in the host->guest
* ring buffer, the host is telling the guest that:
* 1) It will set the pending_send_sz field in the host->guest ring
* buffer when it is waiting for space to become available, and
* 2) It will read the pending_send_sz field in the guest->host
* ring buffer and interrupt the guest when it frees enough space
*
* If either the guest or host does not set the feature bit that it
* owns, that guest or host must do polling if it encounters a full
* ring buffer, and not signal the other end with an interrupt.
*/
u32 pending_send_sz;
u32 reserved1[12];
union {
struct {
u32 feat_pending_send_sz:1;