RE: [PATCH 5/7] Drivers: hv: vmbus: Ignore the offers when resuming from hibernation
From: Michael Kelley <hidden>
Date: 2019-07-30 23:07:14
Also in:
lkml
From: Dexuan Cui <decui@microsoft.com> Sent: Monday, July 8, 2019 10:29 PM
quoted hunk ↗ jump to hunk
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@microsoft.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;
The offermsg contains "reserved" and "padding" fields. Does Hyper-V guarantee that all these fields are the same in the new offer after resuming from hibernation? Or should a less stringent check be made? For example, I could imagine a newer version of Hyper-V allowing a VM that was hibernated on an older version to be resumed. But one of the reserved fields might be used in the newer version, and the comparison could fail unnecessarily.
+
+ 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);The third argument to print_hex_dump() is the rowsize and is specified as must be 16 or 32.
+ return;
+ }
+
/* Allocate the channel object and save this offer. */
newchannel = alloc_channel();
if (!newchannel) {
--
1.8.3.1