linux-kernel - [PATCH 5/7] Drivers: hv: vmbus: Ignore the offers when resuming from hibernation

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Date:   Tue, 9 Jul 2019 05:29:29 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH 5/7] Drivers: hv: vmbus: Ignore the offers when resuming from
 hibernation

When the VM resumes, the host re-sends the offers. We should not add the
offers to the global vmbus_connection.chn_list again.

Added some debug code, in case the host screws up the exact info related to
the offers.

Signed-off-by: Dexuan Cui <decui@...rosoft.com>
---
 drivers/hv/channel_mgmt.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/drivers/hv/channel_mgmt.c b/drivers/hv/channel_mgmt.c
index addcef5..a9aeeab 100644
--- a/drivers/hv/channel_mgmt.c
+++ b/drivers/hv/channel_mgmt.c
@@ -854,12 +854,38 @@ void vmbus_initiate_unload(bool crash)
 static void vmbus_onoffer(struct vmbus_channel_message_header *hdr)
 {
 	struct vmbus_channel_offer_channel *offer;
-	struct vmbus_channel *newchannel;
+	struct vmbus_channel *oldchannel, *newchannel;
+	size_t offer_sz;
 
 	offer = (struct vmbus_channel_offer_channel *)hdr;
 
 	trace_vmbus_onoffer(offer);
 
+	mutex_lock(&vmbus_connection.channel_mutex);
+	oldchannel = relid2channel(offer->child_relid);
+	mutex_unlock(&vmbus_connection.channel_mutex);
+
+	if (oldchannel != NULL) {
+		atomic_dec(&vmbus_connection.offer_in_progress);
+
+		/*
+		 * We're resuming from hibernation: we expect the host to send
+		 * exactly the same offers that we had before the hibernation.
+		 */
+		offer_sz = sizeof(*offer);
+		if (memcmp(offer, &oldchannel->offermsg, offer_sz) == 0)
+			return;
+
+		pr_err("Mismatched offer from the host (relid=%d)!\n",
+		       offer->child_relid);
+
+		print_hex_dump_debug("Old vmbus offer: ", DUMP_PREFIX_OFFSET, 4,
+				     4, &oldchannel->offermsg, offer_sz, false);
+		print_hex_dump_debug("New vmbus offer: ", DUMP_PREFIX_OFFSET, 4,
+				     4, offer, offer_sz, false);
+		return;
+	}
+
 	/* Allocate the channel object and save this offer. */
 	newchannel = alloc_channel();
 	if (!newchannel) {
-- 
1.8.3.1