--- /dev/null
+From c3635da2a336441253c33298b87b3042db100725 Mon Sep 17 00:00:00 2001
+From: Dexuan Cui <decui@microsoft.com>
+Date: Wed, 23 May 2018 21:12:01 +0000
+Subject: PCI: hv: Do not wait forever on a device that has disappeared
+
+From: Dexuan Cui <decui@microsoft.com>
+
+commit c3635da2a336441253c33298b87b3042db100725 upstream.
+
+Before the guest finishes the device initialization, the device can be
+removed anytime by the host, and after that the host won't respond to
+the guest's request, so the guest should be prepared to handle this
+case.
+
+Add a polling mechanism to detect device presence.
+
+Signed-off-by: Dexuan Cui <decui@microsoft.com>
+[lorenzo.pieralisi@arm.com: edited commit log]
+Signed-off-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
+Reviewed-by: Haiyang Zhang <haiyangz@microsoft.com>
+Cc: Stephen Hemminger <sthemmin@microsoft.com>
+Cc: K. Y. Srinivasan <kys@microsoft.com>
+Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
+
+---
+ drivers/pci/host/pci-hyperv.c | 46 +++++++++++++++++++++++++++++++-----------
+ 1 file changed, 34 insertions(+), 12 deletions(-)
+
+--- a/drivers/pci/host/pci-hyperv.c
++++ b/drivers/pci/host/pci-hyperv.c
+@@ -566,6 +566,26 @@ static void put_pcichild(struct hv_pci_d
+ static void get_hvpcibus(struct hv_pcibus_device *hv_pcibus);
+ static void put_hvpcibus(struct hv_pcibus_device *hv_pcibus);
+
++/*
++ * There is no good way to get notified from vmbus_onoffer_rescind(),
++ * so let's use polling here, since this is not a hot path.
++ */
++static int wait_for_response(struct hv_device *hdev,
++ struct completion *comp)
++{
++ while (true) {
++ if (hdev->channel->rescind) {
++ dev_warn_once(&hdev->device, "The device is gone.\n");
++ return -ENODEV;
++ }
++
++ if (wait_for_completion_timeout(comp, HZ / 10))
++ break;
++ }
++
++ return 0;
++}
++
+ /**
+ * devfn_to_wslot() - Convert from Linux PCI slot to Windows
+ * @devfn: The Linux representation of PCI slot
+@@ -1582,7 +1602,8 @@ static struct hv_pci_dev *new_pcichild_d
+ if (ret)
+ goto error;
+
+- wait_for_completion(&comp_pkt.host_event);
++ if (wait_for_response(hbus->hdev, &comp_pkt.host_event))
++ goto error;
+
+ hpdev->desc = *desc;
+ refcount_set(&hpdev->refs, 1);
+@@ -2075,15 +2096,16 @@ static int hv_pci_protocol_negotiation(s
+ sizeof(struct pci_version_request),
+ (unsigned long)pkt, VM_PKT_DATA_INBAND,
+ VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
++ if (!ret)
++ ret = wait_for_response(hdev, &comp_pkt.host_event);
++
+ if (ret) {
+ dev_err(&hdev->device,
+- "PCI Pass-through VSP failed sending version reqquest: %#x",
++ "PCI Pass-through VSP failed to request version: %d",
+ ret);
+ goto exit;
+ }
+
+- wait_for_completion(&comp_pkt.host_event);
+-
+ if (comp_pkt.completion_status >= 0) {
+ pci_protocol_version = pci_protocol_versions[i];
+ dev_info(&hdev->device,
+@@ -2292,11 +2314,12 @@ static int hv_pci_enter_d0(struct hv_dev
+ ret = vmbus_sendpacket(hdev->channel, d0_entry, sizeof(*d0_entry),
+ (unsigned long)pkt, VM_PKT_DATA_INBAND,
+ VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
++ if (!ret)
++ ret = wait_for_response(hdev, &comp_pkt.host_event);
++
+ if (ret)
+ goto exit;
+
+- wait_for_completion(&comp_pkt.host_event);
+-
+ if (comp_pkt.completion_status < 0) {
+ dev_err(&hdev->device,
+ "PCI Pass-through VSP failed D0 Entry with status %x\n",
+@@ -2336,11 +2359,10 @@ static int hv_pci_query_relations(struct
+
+ ret = vmbus_sendpacket(hdev->channel, &message, sizeof(message),
+ 0, VM_PKT_DATA_INBAND, 0);
+- if (ret)
+- return ret;
++ if (!ret)
++ ret = wait_for_response(hdev, &comp);
+
+- wait_for_completion(&comp);
+- return 0;
++ return ret;
+ }
+
+ /**
+@@ -2410,11 +2432,11 @@ static int hv_send_resources_allocated(s
+ size_res, (unsigned long)pkt,
+ VM_PKT_DATA_INBAND,
+ VMBUS_DATA_PACKET_FLAG_COMPLETION_REQUESTED);
++ if (!ret)
++ ret = wait_for_response(hdev, &comp_pkt.host_event);
+ if (ret)
+ break;
+
+- wait_for_completion(&comp_pkt.host_event);
+-
+ if (comp_pkt.completion_status < 0) {
+ ret = -EPROTO;
+ dev_err(&hdev->device,