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authorK. Y. Srinivasan <kys@microsoft.com>2016-11-07 00:14:16 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-11-07 12:01:17 +0300
commit74198eb4a42c4a3c4fbef08fa01a291a282f7c2e (patch)
tree896b7e4abbabdafdd892bbcdfeaff3dbb0258e90 /drivers/hv/channel.c
parent0c38cda64aecb4a821210bb2d3d04092c181c0ae (diff)
downloadlinux-74198eb4a42c4a3c4fbef08fa01a291a282f7c2e.tar.xz
Drivers: hv: vmbus: Base host signaling strictly on the ring state
One of the factors that can result in the host concluding that a given guest in mounting a DOS attack is if the guest generates interrupts to the host when the host is not expecting it. If these "spurious" interrupts reach a certain rate, the host can throttle the guest to minimize the impact. The host computation of the "expected number of interrupts" is strictly based on the ring transitions. Until the host logic is fixed, base the guest logic to interrupt solely on the ring state. Signed-off-by: K. Y. Srinivasan <kys@microsoft.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/hv/channel.c')
-rw-r--r--drivers/hv/channel.c23
1 files changed, 20 insertions, 3 deletions
diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c
index 16f91c8490fe..5e482d7f60cb 100644
--- a/drivers/hv/channel.c
+++ b/drivers/hv/channel.c
@@ -676,10 +676,18 @@ int vmbus_sendpacket_ctl(struct vmbus_channel *channel, void *buffer,
* NOTE: in this case, the hvsock channel is an exception, because
* it looks the host side's hvsock implementation has a throttling
* mechanism which can hurt the performance otherwise.
+ *
+ * KYS: Oct. 30, 2016:
+ * It looks like Windows hosts have logic to deal with DOS attacks that
+ * can be triggered if it receives interrupts when it is not expecting
+ * the interrupt. The host expects interrupts only when the ring
+ * transitions from empty to non-empty (or full to non full on the guest
+ * to host ring).
+ * So, base the signaling decision solely on the ring state until the
+ * host logic is fixed.
*/
- if (((ret == 0) && kick_q && signal) ||
- (ret && !is_hvsock_channel(channel)))
+ if (((ret == 0) && signal))
vmbus_setevent(channel);
return ret;
@@ -786,9 +794,18 @@ int vmbus_sendpacket_pagebuffer_ctl(struct vmbus_channel *channel,
* If we cannot write to the ring-buffer; signal the host
* even if we may not have written anything. This is a rare
* enough condition that it should not matter.
+ *
+ * KYS: Oct. 30, 2016:
+ * It looks like Windows hosts have logic to deal with DOS attacks that
+ * can be triggered if it receives interrupts when it is not expecting
+ * the interrupt. The host expects interrupts only when the ring
+ * transitions from empty to non-empty (or full to non full on the guest
+ * to host ring).
+ * So, base the signaling decision solely on the ring state until the
+ * host logic is fixed.
*/
- if (((ret == 0) && kick_q && signal) || (ret))
+ if (((ret == 0) && signal))
vmbus_setevent(channel);
return ret;