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Diffstat (limited to 'gitlab/issues/target_arm/host_arm/accel_missing/2884.toml')
| -rw-r--r-- | gitlab/issues/target_arm/host_arm/accel_missing/2884.toml | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/gitlab/issues/target_arm/host_arm/accel_missing/2884.toml b/gitlab/issues/target_arm/host_arm/accel_missing/2884.toml new file mode 100644 index 000000000..9f9f7e14c --- /dev/null +++ b/gitlab/issues/target_arm/host_arm/accel_missing/2884.toml @@ -0,0 +1,43 @@ +id = 2884 +title = "Questions about vfio-pci" +state = "opened" +created_at = "2025-03-27T09:32:21.969Z" +closed_at = "n/a" +labels = ["VFIO", "host: arm", "target: arm"] +url = "https://gitlab.com/qemu-project/qemu/-/issues/2884" +host-os = "n/a" +host-arch = "ARM" +qemu-version = "qemu v6.2.0 (qemu v8.2.0 also reproduces)" +guest-os = "n/a" +guest-arch = "n/a" +description = """When I use VFIO-PCI to pass through an hns3 device and load the driver to the VM to enable the hns3 network port, there is a possibility that the failure occurs.""" +reproduce = """1. Start the VM and load the hns3 driver. +2. enable net port + + `ifconfig eth0 10.10.10.10/24 up` +3. ping host + + `ping 10.10.10.11 -c 3`""" +additional = """I have the following findings: + +1. The problem can be reproduced in different kernel versions and QEMU versions. +2. The problem does not recur when the number of vCPUs is 1. +3. It is irrelevant to the GIC version. + +the hns3 relately logic: + +{width="394" height="285"} + +If the VM has two vCPUs, "ifconfig eth0 10.10.10.10/24 up" command performs two sequential enable_irq operations(vector_num=2). The enable_irq will trap into KVM for interrupt configuration and exit to QEMU for PCI device emulation. When emulating interrupt enabling in QEMU, vfio\\_\\[intx/msi/msix\\]\\_enable calls vfio_disable_interrupts to disable all interrupts on the vdev. + +{width="455" height="266"} + +vfio_disable_interrupts in QEMU calls the kernel vfio driver interface vfio_pci_set_irqs_ioctl + +{width="404" height="127"} + +dump stack as above. and then its_irq_domain_deactivate will call its_send_discard to discard the interrupt on the device. + +If an interrupt is handled after the first enable_irq but the second enable_irq discards it, this inconsistency leads to network port enablement failures. + +It puzzles me. why does the vfio-pci disable all interrupts of the device before enabling irqs?""" |