PCI: hv: Add a per-bus mutex state_lock

commit 067d6ec7ed5b49380688e06c1e5f883a71bef4fe upstream.

In the case of fast device addition/removal, it's possible that
hv_eject_device_work() can start to run before create_root_hv_pci_bus()
starts to run; as a result, the pci_get_domain_bus_and_slot() in
hv_eject_device_work() can return a 'pdev' of NULL, and
hv_eject_device_work() can remove the 'hpdev', and immediately send a
message PCI_EJECTION_COMPLETE to the host, and the host immediately
unassigns the PCI device from the guest; meanwhile,
create_root_hv_pci_bus() and the PCI device driver can be probing the
dead PCI device and reporting timeout errors.

Fix the issue by adding a per-bus mutex 'state_lock' and grabbing the
mutex before powering on the PCI bus in hv_pci_enter_d0(): when
hv_eject_device_work() starts to run, it's able to find the 'pdev' and call
pci_stop_and_remove_bus_device(pdev): if the PCI device driver has
loaded, the PCI device driver's probe() function is already called in
create_root_hv_pci_bus() -> pci_bus_add_devices(), and now
hv_eject_device_work() -> pci_stop_and_remove_bus_device() is able
to call the PCI device driver's remove() function and remove the device
reliably; if the PCI device driver hasn't loaded yet, the function call
hv_eject_device_work() -> pci_stop_and_remove_bus_device() is able to
remove the PCI device reliably and the PCI device driver's probe()
function won't be called; if the PCI device driver's probe() is already
running (e.g., systemd-udev is loading the PCI device driver), it must
be holding the per-device lock, and after the probe() finishes and releases
the lock, hv_eject_device_work() -> pci_stop_and_remove_bus_device() is
able to proceed to remove the device reliably.

Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs")
Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Acked-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20230615044451.5580-6-decui@microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c
index 6f6b30c..3351863 100644 (file)
--- a/drivers/pci/controller/pci-hyperv.c
+++ b/drivers/pci/controller/pci-hyperv.c
@@ -489,7 +489,10 @@ struct hv_pcibus_device {
        struct fwnode_handle *fwnode;
        /* Protocol version negotiated with the host */
        enum pci_protocol_version_t protocol_version;
+
+       struct mutex state_lock;
        enum hv_pcibus_state state;
+
        struct hv_device *hdev;
        resource_size_t low_mmio_space;
        resource_size_t high_mmio_space;
@@ -2525,6 +2528,8 @@ static void pci_devices_present_work(struct work_struct *work)
        if (!dr)
                return;
 
+       mutex_lock(&hbus->state_lock);
+
        /* First, mark all existing children as reported missing. */
        spin_lock_irqsave(&hbus->device_list_lock, flags);
        list_for_each_entry(hpdev, &hbus->children, list_entry) {
@@ -2606,6 +2611,8 @@ static void pci_devices_present_work(struct work_struct *work)
                break;
        }
 
+       mutex_unlock(&hbus->state_lock);
+
        kfree(dr);
 }
 
@@ -2754,6 +2761,8 @@ static void hv_eject_device_work(struct work_struct *work)
        hpdev = container_of(work, struct hv_pci_dev, wrk);
        hbus = hpdev->hbus;
 
+       mutex_lock(&hbus->state_lock);
+
        /*
         * Ejection can come before or after the PCI bus has been set up, so
         * attempt to find it and tear down the bus state, if it exists.  This
@@ -2790,6 +2799,8 @@ static void hv_eject_device_work(struct work_struct *work)
        put_pcichild(hpdev);
        put_pcichild(hpdev);
        /* hpdev has been freed. Do not use it any more. */
+
+       mutex_unlock(&hbus->state_lock);
 }
 
 /**
@@ -3580,6 +3591,7 @@ static int hv_pci_probe(struct hv_device *hdev,
                return -ENOMEM;
 
        hbus->bridge = bridge;
+       mutex_init(&hbus->state_lock);
        hbus->state = hv_pcibus_init;
        hbus->wslot_res_allocated = -1;
 
@@ -3688,9 +3700,11 @@ static int hv_pci_probe(struct hv_device *hdev,
        if (ret)
                goto free_irq_domain;
 
+       mutex_lock(&hbus->state_lock);
+
        ret = hv_pci_enter_d0(hdev);
        if (ret)
-               goto free_irq_domain;
+               goto release_state_lock;
 
        ret = hv_pci_allocate_bridge_windows(hbus);
        if (ret)
@@ -3708,12 +3722,15 @@ static int hv_pci_probe(struct hv_device *hdev,
        if (ret)
                goto free_windows;
 
+       mutex_unlock(&hbus->state_lock);
        return 0;
 
 free_windows:
        hv_pci_free_bridge_windows(hbus);
 exit_d0:
        (void) hv_pci_bus_exit(hdev, true);
+release_state_lock:
+       mutex_unlock(&hbus->state_lock);
 free_irq_domain:
        irq_domain_remove(hbus->irq_domain);
 free_fwnode:
@@ -3967,20 +3984,26 @@ static int hv_pci_resume(struct hv_device *hdev)
        if (ret)
                goto out;
 
+       mutex_lock(&hbus->state_lock);
+
        ret = hv_pci_enter_d0(hdev);
        if (ret)
-               goto out;
+               goto release_state_lock;
 
        ret = hv_send_resources_allocated(hdev);
        if (ret)
-               goto out;
+               goto release_state_lock;
 
        prepopulate_bars(hbus);
 
        hv_pci_restore_msi_state(hbus);
 
        hbus->state = hv_pcibus_installed;
+       mutex_unlock(&hbus->state_lock);
        return 0;
+
+release_state_lock:
+       mutex_unlock(&hbus->state_lock);
 out:
        vmbus_close(hdev->channel);
        return ret;