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 --- include/linux/hyperv.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux') diff --git a/include/linux/hyperv.h b/include/linux/hyperv.h index dfc516c1c719..5459e776ec17 100644 --- a/include/linux/hyperv.h +++ b/include/linux/hyperv.h @@ -1304,6 +1304,8 @@ static inline void *hv_get_drvdata(struct hv_device *dev) struct device *hv_get_vmbus_root_device(void); +bool hv_vmbus_exists(void); + struct hv_ring_buffer_debug_info { u32 current_interrupt_mask; u32 current_read_index; -- cgit v1.2.3