From e67ad058e45aa8b23e9b94e793b9fcf66e70ebb0 Mon Sep 17 00:00:00 2001 From: Matthew Rosato Date: Mon, 16 Nov 2020 16:42:35 -0500 Subject: [PATCH] s390x/pci: Unregister listeners before destroying IOMMU address space Hot-unplugging a vfio-pci device on s390x causes a QEMU crash: qemu-system-s390x: ../softmmu/memory.c:2772: do_address_space_destroy: Assertion `QTAILQ_EMPTY(&as->listeners)' failed. In s390, the IOMMU address space is freed during device unplug but the associated vfio-pci device may not yet be finalized and therefore may still have a listener registered to the IOMMU address space. Commit a2166410ad74 ("spapr_pci: Unregister listeners before destroying the IOMMU address space") previously resolved this issue for spapr_pci. We are now seeing this in s390x; it would seem the possibility for this issue was already present but based on a bisect commit 2d24a6466154 ("device-core: use RCU for list of children of a bus") has now changed the timing such that it is now readily reproducible. Add logic to ensure listeners are removed before destroying the address space. Reported-by: Niklas Schnelle Signed-off-by: Matthew Rosato Tested-by: Niklas Schnelle Reviewed-by: Pierre Morel Reviewed-by: Thomas Huth Message-Id: <1605562955-21152-1-git-send-email-mjrosato@linux.ibm.com> Signed-off-by: Cornelia Huck --- hw/s390x/s390-pci-bus.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/hw/s390x/s390-pci-bus.c b/hw/s390x/s390-pci-bus.c index 48a3be802f..e0dc20ce4a 100644 --- a/hw/s390x/s390-pci-bus.c +++ b/hw/s390x/s390-pci-bus.c @@ -732,6 +732,13 @@ static void s390_pci_iommu_free(S390pciState *s, PCIBus *bus, int32_t devfn) table->iommu[PCI_SLOT(devfn)] = NULL; g_hash_table_destroy(iommu->iotlb); + /* + * An attached PCI device may have memory listeners, eg. VFIO PCI. + * The associated subregion will already have been unmapped in + * s390_pci_iommu_disable in response to the guest deconfigure request. + * Remove the listeners now before destroying the address space. + */ + address_space_remove_listeners(&iommu->as); address_space_destroy(&iommu->as); object_unparent(OBJECT(&iommu->mr)); object_unparent(OBJECT(iommu));