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Drivers: hv: vmbus: finally fix hv_need_to_signal_on_read()

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Commit a389fcfd2c ("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: a389fcfd2c ("Drivers: hv: vmbus: Fix signaling logic in
hv_need_to_signal_on_read()")

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reported-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Tested-by: Rolf Neugebauer <rolf.neugebauer@docker.com>
Cc: "K. Y. Srinivasan" <kys@microsoft.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Dexuan Cui 2017-01-28 11:46:02 -07:00 • committed by Greg Kroah-Hartman
parent 191e885a2e
commit 433e19cf33
3 changed files with 37 additions and 2 deletions
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6
drivers/net/hyperv/netvsc.c
View file

@ -1295,6 +1295,9 @@ void netvsc_channel_cb(void *context)
ndev = hv_get_drvdata(device);
buffer = get_per_channel_state(channel);
/* commit_rd_index() -> hv_signal_on_read() needs this. */
init_cached_read_index(channel);
do {
desc = get_next_pkt_raw(channel);
if (desc != NULL) {
@ -1347,6 +1350,9 @@ void netvsc_channel_cb(void *context)
bufferlen = bytes_recvd;
}
init_cached_read_index(channel);
} while (1);
if (bufferlen > NETVSC_PACKET_SIZE)