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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 a2166410ad ("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 2d24a64661
("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 <schnelle@linux.ibm.com>
Signed-off-by: Matthew Rosato <mjrosato@linux.ibm.com>
Tested-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Pierre Morel <pmorel@linux.ibm.com>
Reviewed-by: Thomas Huth <thuth@redhat.com>
Message-Id: <1605562955-21152-1-git-send-email-mjrosato@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
This commit is contained in:
Matthew Rosato 2020-11-16 16:42:35 -05:00 committed by Cornelia Huck
parent e2c6cd5674
commit e67ad058e4
1 changed files with 7 additions and 0 deletions
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7
hw/s390x/s390-pci-bus.c
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@ -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));