[PATCH v3 6/6] PCI: hv: fix 2 hang issues in hv_compose_msi_msg()

Dexuan Cui
2018-03-06T18:21:56Z

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 <decui@microsoft.com>
Tested-by: Adrian Suhov <v-adsuho@microsoft.com>
Tested-by: Chris Valean <v-chvale@microsoft.com>
Cc: stable@vger.kernel.org
Cc: Stephen Hemminger <sthemmin@microsoft.com>
Cc: K. Y. Srinivasan <kys@microsoft.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Jack Morgenstein <jackm@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
_______________________________________________
devel mailing list
devel@linuxdriverproject.org