kernel/linux.git/drivers/pci/controller/pci-hyperv.c, branch v6.12.80

PCI: hv: Return zero, not garbage, when reading PCI_INTERRUPT_PIN

2024-07-03T21:11:14+00:00

The intent of the code snippet is to always return 0 for both PCI_INTERRUPT_LINE and PCI_INTERRUPT_PIN. The check misses PCI_INTERRUPT_PIN. This patch fixes that. This is discovered by this call in VFIO: pci_read_config_byte(vdev->pdev, PCI_INTERRUPT_PIN, &pin); The old code does not set *val to 0 because it misses the check for PCI_INTERRUPT_PIN. Garbage is returned in that case. Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs") Link: https://lore.kernel.org/linux-pci/20240701202606.129606-1-wei.liu@kernel.org Signed-off-by: Wei Liu Signed-off-by: Krzysztof Wilczyński Reviewed-by: Michael Kelley Cc: stable@kernel.org

PCI: hv: Fix ring buffer size calculation

2024-03-10T18:54:12+00:00

For a physical PCI device that is passed through to a Hyper-V guest VM, current code specifies the VMBus ring buffer size as 4 pages. But this is an inappropriate dependency, since the amount of ring buffer space needed is unrelated to PAGE_SIZE. For example, on x86 the ring buffer size ends up as 16 Kbytes, while on ARM64 with 64 Kbyte pages, the ring size bloats to 256 Kbytes. The ring buffer for PCI pass-thru devices is used for only a few messages during device setup and removal, so any space above a few Kbytes is wasted. Fix this by declaring the ring buffer size to be a fixed 16 Kbytes. Furthermore, use the VMBUS_RING_SIZE() macro so that the ring buffer header is properly accounted for, and so the size is rounded up to a page boundary, using the page size for which the kernel is built. While w/64 Kbyte pages this results in a 64 Kbyte ring buffer header plus a 64 Kbyte ring buffer, that's the smallest possible with that page size. It's still 128 Kbytes better than the current code. Link: https://lore.kernel.org/linux-pci/20240216202240.251818-1-mhklinux@outlook.com Signed-off-by: Michael Kelley Signed-off-by: Krzysztof Wilczyński Reviewed-by: Kuppuswamy Sathyanarayanan Reviewed-by: Ilpo Jarvinen Reviewed-by: Long Li Cc: # 5.15.x

x86/apic: Drop apic::delivery_mode

2023-11-21T15:58:54+00:00

This field is set to APIC_DELIVERY_MODE_FIXED in all cases, and is read exactly once. Fold the constant in uv_program_mmr() and drop the field. Searching for the origin of the stale HyperV comment reveals commit a31e58e129f7 ("x86/apic: Switch all APICs to Fixed delivery mode") which notes: As a consequence of this change, the apic::irq_delivery_mode field is now pointless, but this needs to be cleaned up in a separate patch. 6 years is long enough for this technical debt to have survived. [ bp: Fold in https://lore.kernel.org/r/20231121123034.1442059-1-andrew.cooper3@citrix.com ] Signed-off-by: Andrew Cooper Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov (AMD) Reviewed-by: Steve Wahl Link: https://lore.kernel.org/r/20231102-x86-apic-v1-1-bf049a2a0ed6@citrix.com

PCI: hv: Annotate struct hv_dr_state with __counted_by

2023-10-14T20:02:55+00:00

Prepare for the coming implementation by GCC and Clang of the __counted_by attribute. Flexible array members annotated with __counted_by can have their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family functions). As found with Coccinelle[1], add __counted_by for struct hv_dr_state. [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci Link: https://lore.kernel.org/linux-pci/20230922175257.work.900-kees@kernel.org Signed-off-by: Kees Cook Signed-off-by: Krzysztof Wilczyński Reviewed-by: "Gustavo A. R. Silva" Acked-by: Wei Liu Cc: Bjorn Helgaas Cc: Dexuan Cui Cc: Haiyang Zhang Cc: "K. Y. Srinivasan" Cc: Krzysztof Wilczyński Cc: Lorenzo Pieralisi Cc: Rob Herring Cc: Wei Liu Cc: linux-hyperv@vger.kernel.org Cc: linux-pci@vger.kernel.org

PCI: hv: Fix a crash in hv_pci_restore_msi_msg() during hibernation

2023-08-22T13:03:11+00:00

When a Linux VM with an assigned PCI device runs on Hyper-V, if the PCI device driver is not loaded yet (i.e. MSI-X/MSI is not enabled on the device yet), doing a VM hibernation triggers a panic in hv_pci_restore_msi_msg() -> msi_lock_descs(&pdev->dev), because pdev->dev.msi.data is still NULL. Avoid the panic by checking if MSI-X/MSI is enabled. Link: https://lore.kernel.org/r/20230816175939.21566-1-decui@microsoft.com Fixes: dc2b453290c4 ("PCI: hv: Rework MSI handling") Signed-off-by: Dexuan Cui Signed-off-by: Lorenzo Pieralisi Reviewed-by: sathyanarayanan.kuppuswamy@linux.intel.com Reviewed-by: Michael Kelley Cc: stable@vger.kernel.org

PCI: hv: Add a per-bus mutex state_lock

2023-06-18T03:05:40+00:00

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 Reviewed-by: Michael Kelley Acked-by: Lorenzo Pieralisi Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230615044451.5580-6-decui@microsoft.com Signed-off-by: Wei Liu

Revert "PCI: hv: Fix a timing issue which causes kdump to fail occasionally"

2023-06-18T03:05:39+00:00

This reverts commit d6af2ed29c7c1c311b96dac989dcb991e90ee195. The statement "the hv_pci_bus_exit() call releases structures of all its child devices" in commit d6af2ed29c7c is not true: in the path hv_pci_probe() -> hv_pci_enter_d0() -> hv_pci_bus_exit(hdev, true): the parameter "keep_devs" is true, so hv_pci_bus_exit() does *not* release the child "struct hv_pci_dev *hpdev" that is created earlier in pci_devices_present_work() -> new_pcichild_device(). The commit d6af2ed29c7c was originally made in July 2020 for RHEL 7.7, where the old version of hv_pci_bus_exit() was used; when the commit was rebased and merged into the upstream, people didn't notice that it's not really necessary. The commit itself doesn't cause any issue, but it makes hv_pci_probe() more complicated. Revert it to facilitate some upcoming changes to hv_pci_probe(). Signed-off-by: Dexuan Cui Reviewed-by: Michael Kelley Acked-by: Wei Hu Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230615044451.5580-5-decui@microsoft.com Signed-off-by: Wei Liu

PCI: hv: Remove the useless hv_pcichild_state from struct hv_pci_dev

2023-06-18T03:05:39+00:00

The hpdev->state is never really useful. The only use in hv_pci_eject_device() and hv_eject_device_work() is not really necessary. Signed-off-by: Dexuan Cui Reviewed-by: Michael Kelley Acked-by: Lorenzo Pieralisi Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230615044451.5580-4-decui@microsoft.com Signed-off-by: Wei Liu

PCI: hv: Fix a race condition in hv_irq_unmask() that can cause panic

2023-06-18T03:05:39+00:00

When the host tries to remove a PCI device, the host first sends a PCI_EJECT message to the guest, and the guest is supposed to gracefully remove the PCI device and send a PCI_EJECTION_COMPLETE message to the host; the host then sends a VMBus message CHANNELMSG_RESCIND_CHANNELOFFER to the guest (when the guest receives this message, the device is already unassigned from the guest) and the guest can do some final cleanup work; if the guest fails to respond to the PCI_EJECT message within one minute, the host sends the VMBus message CHANNELMSG_RESCIND_CHANNELOFFER and removes the PCI device forcibly. In the case of fast device addition/removal, it's possible that the PCI device driver is still configuring MSI-X interrupts when the guest receives the PCI_EJECT message; the channel callback calls hv_pci_eject_device(), which sets hpdev->state to hv_pcichild_ejecting, and schedules a work hv_eject_device_work(); if the PCI device driver is calling pci_alloc_irq_vectors() -> ... -> hv_compose_msi_msg(), we can break the while loop in hv_compose_msi_msg() due to the updated hpdev->state, and leave data->chip_data with its default value of NULL; later, when the PCI device driver calls request_irq() -> ... -> hv_irq_unmask(), the guest crashes in hv_arch_irq_unmask() due to data->chip_data being NULL. Fix the issue by not testing hpdev->state in the while loop: when the guest receives PCI_EJECT, the device is still assigned to the guest, and the guest has one minute to finish the device removal gracefully. We don't really need to (and we should not) test hpdev->state in the loop. Fixes: de0aa7b2f97d ("PCI: hv: Fix 2 hang issues in hv_compose_msi_msg()") Signed-off-by: Dexuan Cui Reviewed-by: Michael Kelley Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230615044451.5580-3-decui@microsoft.com Signed-off-by: Wei Liu

PCI: hv: Fix a race condition bug in hv_pci_query_relations()

2023-06-18T03:05:39+00:00

Since day 1 of the driver, there has been a race between hv_pci_query_relations() and survey_child_resources(): during fast device hotplug, hv_pci_query_relations() may error out due to device-remove and the stack variable 'comp' is no longer valid; however, pci_devices_present_work() -> survey_child_resources() -> complete() may be running on another CPU and accessing the no-longer-valid 'comp'. Fix the race by flushing the workqueue before we exit from hv_pci_query_relations(). Fixes: 4daace0d8ce8 ("PCI: hv: Add paravirtual PCI front-end for Microsoft Hyper-V VMs") Signed-off-by: Dexuan Cui Reviewed-by: Michael Kelley Acked-by: Lorenzo Pieralisi Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20230615044451.5580-2-decui@microsoft.com Signed-off-by: Wei Liu