From 0d5acba6331c326f394a677daf49a67f44a0416a Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Thu, 9 Apr 2026 14:52:32 -0700 Subject: Drivers: hv: vmbus: Export hv_vmbus_exists() and use it in pci-hyperv With commit f84b21da3624 ("PCI: hv: Don't load the driver for baremetal root partition"), the bare metal Linux root partition won't use the pci-hyperv driver, but when a Linux VM runs on the Linux root partition, pci-hyperv's module_init function init_hv_pci_drv() can still run, e.g. in the case of CONFIG_PCI_HYPERV=y, even if the VMBus driver is not used in such a VM (i.e. the hv_vmbus driver's init function returns -ENODEV due to vmbus_root_device being NULL). In such a Linux VM, init_hv_pci_drv() runs with a side effect: the 3 hvpci_block_ops callbacks are set to functions that depend on hv_vmbus. Later, when the MLX driver in such a VM invokes the callbacks, e.g. in drivers/net/ethernet/mellanox/mlx5/core/lib/hv.c: mlx5_hv_register_invalidate(), hvpci_block_ops.reg_blk_invalidate() is hv_register_block_invalidate() rather than a NULL function pointer, and hv_register_block_invalidate() assumes that it can find a struct hv_pcibus_device from pdev->bus->sysdata, which is false in such a VM. Consequently, hv_register_block_invalidate() -> get_pcichild_wslot() -> spin_lock_irqsave() may hang since it can be accessing an invalid spinlock pointer. Fix the issue by exporting hv_vmbus_exists() and using it in pci-hyperv: hv_root_partition() is true and hv_nested is false ==> hv_vmbus_exists() is false. hv_root_partition() is true and hv_nested is true ==> hv_vmbus_exists() is true. hv_root_partition() is false ==> hv_vmbus_exists() is true. While at it, rename vmbus_exists() to hv_vmbus_exists() to follow the convention that all public functions have the hv_ prefix; also change the return value's type from int to bool to make the code more readable; also move the two pr_info() calls. Reported-by: Mukesh Rathor Signed-off-by: Dexuan Cui Signed-off-by: Wei Liu --- drivers/hv/vmbus_drv.c | 20 ++++++++------------ drivers/pci/controller/pci-hyperv.c | 2 +- 2 files changed, 9 insertions(+), 13 deletions(-) (limited to 'drivers') diff --git a/drivers/hv/vmbus_drv.c b/drivers/hv/vmbus_drv.c index 3d1a58b667db..24fa0b2443c3 100644 --- a/drivers/hv/vmbus_drv.c +++ b/drivers/hv/vmbus_drv.c @@ -101,13 +101,11 @@ struct device *hv_get_vmbus_root_device(void) } EXPORT_SYMBOL_GPL(hv_get_vmbus_root_device); -static int vmbus_exists(void) +bool hv_vmbus_exists(void) { - if (vmbus_root_device == NULL) - return -ENODEV; - - return 0; + return vmbus_root_device != NULL; } +EXPORT_SYMBOL_GPL(hv_vmbus_exists); static u8 channel_monitor_group(const struct vmbus_channel *channel) { @@ -1577,11 +1575,10 @@ int __vmbus_driver_register(struct hv_driver *hv_driver, struct module *owner, c { int ret; - pr_info("registering driver %s\n", hv_driver->name); + if (!hv_vmbus_exists()) + return -ENODEV; - ret = vmbus_exists(); - if (ret < 0) - return ret; + pr_info("registering driver %s\n", hv_driver->name); hv_driver->driver.name = hv_driver->name; hv_driver->driver.owner = owner; @@ -1607,9 +1604,8 @@ EXPORT_SYMBOL_GPL(__vmbus_driver_register); */ void vmbus_driver_unregister(struct hv_driver *hv_driver) { - pr_info("unregistering driver %s\n", hv_driver->name); - - if (!vmbus_exists()) { + if (hv_vmbus_exists()) { + pr_info("unregistering driver %s\n", hv_driver->name); driver_unregister(&hv_driver->driver); vmbus_free_dynids(hv_driver); } diff --git a/drivers/pci/controller/pci-hyperv.c b/drivers/pci/controller/pci-hyperv.c index 49c0a2d51162..cfc8fa403dad 100644 --- a/drivers/pci/controller/pci-hyperv.c +++ b/drivers/pci/controller/pci-hyperv.c @@ -4172,7 +4172,7 @@ static int __init init_hv_pci_drv(void) if (!hv_is_hyperv_initialized()) return -ENODEV; - if (hv_root_partition() && !hv_nested) + if (!hv_vmbus_exists()) return -ENODEV; ret = hv_pci_irqchip_init(); -- cgit v1.2.3