1. With the patch "x86/vector/msi: Switch to global reservation mode"
(4900be8360), the recent v4.15 and newer kernels always hang for 1-vCPU
Hyper-V VM with SR-IOV. This is because when we reach hv_compose_msi_msg()
by request_irq()  -> request_threaded_irq() -> __setup_irq()->irq_startup()
 -> __irq_startup() -> irq_domain_activate_irq() -> ... ->
msi_domain_activate() -> ... -> hv_compose_msi_msg(), local irq is
disabled in __setup_irq().

Fix this by polling the channel.

2. If the host is ejecting the VF device before we reach
hv_compose_msi_msg(), in a UP VM, we can hang in hv_compose_msi_msg()
forever, because at this time the host doesn't respond to the
CREATE_INTERRUPT request. This issue also happens to old kernels like
v4.14, v4.13, etc.

Fix this by polling the channel for the PCI_EJECT message and
hpdev->state, and by checking the PCI vendor ID.

Note: actually the above issues also happen to a SMP VM, if
"hbus->hdev->channel->target_cpu == smp_processor_id()" is true.

Signed-off-by: Dexuan Cui <de...@microsoft.com>
Tested-by: Adrian Suhov <v-ads...@microsoft.com>
Tested-by: Chris Valean <v-chv...@microsoft.com>
Cc: sta...@vger.kernel.org
Cc: Stephen Hemminger <sthem...@microsoft.com>
Cc: K. Y. Srinivasan <k...@microsoft.com>
Cc: Vitaly Kuznetsov <vkuzn...@redhat.com>
Cc: Jack Morgenstein <ja...@mellanox.com>
---
 drivers/pci/host/pci-hyperv.c | 58 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 57 insertions(+), 1 deletion(-)

diff --git a/drivers/pci/host/pci-hyperv.c b/drivers/pci/host/pci-hyperv.c
index 265ba11e53e2..50cdefe3f6d3 100644
--- a/drivers/pci/host/pci-hyperv.c
+++ b/drivers/pci/host/pci-hyperv.c
@@ -521,6 +521,8 @@ struct hv_pci_compl {
        s32 completion_status;
 };
 
+static void hv_pci_onchannelcallback(void *context);
+
 /**
  * hv_pci_generic_compl() - Invoked for a completion packet
  * @context:           Set up by the sender of the packet.
@@ -665,6 +667,31 @@ static void _hv_pcifront_read_config(struct hv_pci_dev 
*hpdev, int where,
        }
 }
 
+static u16 hv_pcifront_get_vendor_id(struct hv_pci_dev *hpdev)
+{
+       u16 ret;
+       unsigned long flags;
+       void __iomem *addr = hpdev->hbus->cfg_addr + CFG_PAGE_OFFSET +
+                            PCI_VENDOR_ID;
+
+       spin_lock_irqsave(&hpdev->hbus->config_lock, flags);
+
+       /* Choose the function to be read. (See comment above) */
+       writel(hpdev->desc.win_slot.slot, hpdev->hbus->cfg_addr);
+       /* Make sure the function was chosen before we start reading. */
+       mb();
+       /* Read from that function's config space. */
+       ret = readw(addr);
+       /*
+        * mb() is not required here, because the spin_unlock_irqrestore()
+        * is a barrier.
+        */
+
+       spin_unlock_irqrestore(&hpdev->hbus->config_lock, flags);
+
+       return ret;
+}
+
 /**
  * _hv_pcifront_write_config() - Internal PCI config write
  * @hpdev:     The PCI driver's representation of the device
@@ -1107,8 +1134,37 @@ static void hv_compose_msi_msg(struct irq_data *data, 
struct msi_msg *msg)
         * Since this function is called with IRQ locks held, can't
         * do normal wait for completion; instead poll.
         */
-       while (!try_wait_for_completion(&comp.comp_pkt.host_event))
+       while (!try_wait_for_completion(&comp.comp_pkt.host_event)) {
+               /* 0xFFFF means an invalid PCI VENDOR ID. */
+               if (hv_pcifront_get_vendor_id(hpdev) == 0xFFFF) {
+                       dev_err_once(&hbus->hdev->device,
+                                    "the device has gone\n");
+                       goto free_int_desc;
+               }
+
+               /*
+                * When the higher level interrupt code calls us with
+                * interrupt disabled, we must poll the channel by calling
+                * the channel callback directly when channel->target_cpu is
+                * the current CPU. When the higher level interrupt code
+                * calls us with interrupt enabled, let's add the
+                * local_bh_disable()/enable() to avoid race.
+                */
+               local_bh_disable();
+
+               if (hbus->hdev->channel->target_cpu == smp_processor_id())
+                       hv_pci_onchannelcallback(hbus);
+
+               local_bh_enable();
+
+               if (hpdev->state == hv_pcichild_ejecting) {
+                       dev_err_once(&hbus->hdev->device,
+                                    "the device is being ejected\n");
+                       goto free_int_desc;
+               }
+
                udelay(100);
+       }
 
        if (comp.comp_pkt.completion_status < 0) {
                dev_err(&hbus->hdev->device,
-- 
2.7.4

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