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Groups > linux.kernel > #1513420
| From | kys@exchange.microsoft.com |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH V2 12/14] Drivers: hv: vmbus: Base host signaling strictly on the ring state |
| Date | 2016-11-01 19:20 +0100 |
| Message-ID | <syLPc-3J3-25@gated-at.bofh.it> (permalink) |
| References | <syLPb-3J3-1@gated-at.bofh.it> <syLPc-3J3-7@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
From: K. Y. Srinivasan <kys@microsoft.com> 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> --- drivers/hv/channel.c | 23 ++++++++++++++++++++--- drivers/hv/channel_mgmt.c | 2 -- drivers/hv/ring_buffer.c | 7 ------- 3 files changed, 20 insertions(+), 12 deletions(-) diff --git a/drivers/hv/channel.c b/drivers/hv/channel.c index 16f91c8..5e482d7 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; diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c index 96a85cd..cbb96f2 100644 --- a/drivers/hv/channel_mgmt.c +++ b/drivers/hv/channel_mgmt.c @@ -447,8 +447,6 @@ static void vmbus_process_offer(struct vmbus_channel *newchannel) } dev_type = hv_get_dev_type(newchannel); - if (dev_type == HV_NIC) - set_channel_signal_state(newchannel, HV_SIGNAL_POLICY_EXPLICIT); init_vp_index(newchannel, dev_type); diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c index 08043da..5d11d93 100644 --- a/drivers/hv/ring_buffer.c +++ b/drivers/hv/ring_buffer.c @@ -75,13 +75,6 @@ static bool hv_need_to_signal(u32 old_write, struct hv_ring_buffer_info *rbi, if (READ_ONCE(rbi->ring_buffer->interrupt_mask)) return false; - /* - * When the client wants to control signaling, - * we only honour the host interrupt mask. - */ - if (policy == HV_SIGNAL_POLICY_EXPLICIT) - return true; - /* check interrupt_mask before read_index */ virt_rmb(); /* -- 1.7.4.1
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[PATCH V2 00/14] Drivers: hv: Some miscellaneous fixes and enhancements kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 08/14] Drivers: hv: balloon: Fix info request to show max page count kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
Re: [PATCH V2 08/14] Drivers: hv: balloon: Fix info request to show max page count Dan Carpenter <dan.carpenter@oracle.com> - 2016-11-10 20:20 +0100
RE: [PATCH V2 08/14] Drivers: hv: balloon: Fix info request to show max page count "Alex Ng (LIS)" <alexng@microsoft.com> - 2016-11-11 00:20 +0100
[PATCH V2 04/14] Drivers: hv: balloon: Disable hot add when CONFIG_MEMORY_HOTPLUG is not set kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 02/14] Drivers: hv: utils: reduce HV_UTIL_NEGO_TIMEOUT timeout kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 12/14] Drivers: hv: vmbus: Base host signaling strictly on the ring state kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 03/14] Drivers: hv: utils: Fix the mapping between host version and protocol to use kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 11/14] tools: hv: remove unnecessary header files and netlink related code kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 14/14] Drivers: hv: vmbus: On the read path cleanup the logic to interrupt the host kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 07/14] Drivers: hv: vss: Operation timeouts should match host expectation kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 01/14] Drivers: hv: ring_buffer: count on wrap around mappings in get_next_pkt_raw() (v2) kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 10/14] tools: hv: fix a compile warning in snprintf kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 06/14] Drivers: hv: vss: Improve log messages. kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 09/14] tools: hv: remove unnecessary link flag kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 13/14] Drivers: hv: vmbus: On write cleanup the logic to interrupt the host kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
[PATCH V2 05/14] Drivers: hv: balloon: Add logging for dynamic memory operations kys@exchange.microsoft.com - 2016-11-01 19:20 +0100
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