History

Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read()

Commit a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()") added the proper mb(), but removed the test "prev_write_sz < pending_sz" when making the signal decision. As a result, the guest can signal the host unnecessarily, and then the host can throttle the guest because the host thinks the guest is buggy or malicious; finally the user running stress test can perceive intermittent freeze of the guest. This patch brings back the test, and properly handles the in-place consumption APIs used by NetVSC (see get_next_pkt_raw(), put_pkt_raw() and commit_rd_index()). Fixes: a389fcfd2cb5 ("Drivers: hv: vmbus: Fix signaling logic in hv_need_to_signal_on_read()")

Dexuan Cui committed 9 years ago

Commit 433e19c1 parent 191e8853 files · +37 −2Browse files

Showing the changes to include/linux (1 of 3 files). Show all

Unified · Split

include/linux/hyperv.h+30−2
@@ -128,6 +128,7 @@ struct hv_ring_buffer_info { · 127 unmodified lines
128 u32 ring_data_startoffset;128 u32 ring_data_startoffset;
129 u32 priv_write_index;129 u32 priv_write_index;
130 u32 priv_read_index;130 u32 priv_read_index;
131 u32 cached_read_index;
131};132};
132 133
133/*134/*
@@ -180,6 +181,19 @@ static inline u32 hv_get_bytes_to_write(struct hv_ring_buffer_info *rbi) · 46 unmodified lines
180 return write;181 return write;
181}182}
182 183
184static inline u32 hv_get_cached_bytes_to_write(
185 const struct hv_ring_buffer_info *rbi)
186{
187 u32 read_loc, write_loc, dsize, write;
188
189 dsize = rbi->ring_datasize;
190 read_loc = rbi->cached_read_index;
191 write_loc = rbi->ring_buffer->write_index;
192
193 write = write_loc >= read_loc ? dsize - (write_loc - read_loc) :
194 read_loc - write_loc;
195 return write;
196}
183/*197/*
184 * VMBUS version is 32 bit entity broken up into198 * VMBUS version is 32 bit entity broken up into
185 * two 16 bit quantities: major_number. minor_number.199 * two 16 bit quantities: major_number. minor_number.
@@ -1488,7 +1502,7 @@ hv_get_ring_buffer(struct hv_ring_buffer_info *ring_info) · 1302 unmodified lines
1488 1502
1489static inline void hv_signal_on_read(struct vmbus_channel *channel)1503static inline void hv_signal_on_read(struct vmbus_channel *channel)
1490{1504{
1491 u32 cur_write_sz;1505 u32 cur_write_sz, cached_write_sz;
1492 u32 pending_sz;1506 u32 pending_sz;
1493 struct hv_ring_buffer_info *rbi = &channel->inbound;1507 struct hv_ring_buffer_info *rbi = &channel->inbound;
1494 1508
@@ -1512,12 +1526,24 @@ static inline void hv_signal_on_read(struct vmbus_channel *channel) · 17 unmodified lines
1512 1526
1513 cur_write_sz = hv_get_bytes_to_write(rbi);1527 cur_write_sz = hv_get_bytes_to_write(rbi);
1514 1528
1515 if (cur_write_sz >= pending_sz)1529 if (cur_write_sz < pending_sz)
1530 return;
1531
1532 cached_write_sz = hv_get_cached_bytes_to_write(rbi);
1533 if (cached_write_sz < pending_sz)
1516 vmbus_setevent(channel);1534 vmbus_setevent(channel);
1517 1535
1518 return;1536 return;
1519}1537}
1520 1538
1539static inline void
1540init_cached_read_index(struct vmbus_channel *channel)
1541{
1542 struct hv_ring_buffer_info *rbi = &channel->inbound;
1543
1544 rbi->cached_read_index = rbi->ring_buffer->read_index;
1545}
1546
1521/*1547/*
1522 * An API to support in-place processing of incoming VMBUS packets.1548 * An API to support in-place processing of incoming VMBUS packets.
1523 */1549 */
@@ -1569,6 +1595,8 @@ static inline void put_pkt_raw(struct vmbus_channel *channel, · 45 unmodified lines
1569 * This call commits the read index and potentially signals the host.1595 * This call commits the read index and potentially signals the host.
1570 * Here is the pattern for using the "in-place" consumption APIs:1596 * Here is the pattern for using the "in-place" consumption APIs:
1571 *1597 *
1598 * init_cached_read_index();
1599 *
1572 * while (get_next_pkt_raw() {1600 * while (get_next_pkt_raw() {
1573 * process the packet "in-place";1601 * process the packet "in-place";
1574 * put_pkt_raw();1602 * put_pkt_raw();