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Description: s390/pci: vfio-pci mmio being disabled erroneously
Symptom: PCI virtual functions passed through via vfio-pci are unusable
Problem: The fix for CVE-2020-12888 'abafbc551fdd vfio-pci: Invalidate
mmaps and block MMIO access on disabled memory' introduced an
issue which prevented PCI Virtual Functions from being passed-
through via vfio-pci as VFs are not allowed to have the
PCI_COMMAND_MEMORY bit enabled per spec. This issue was
initially thought to be fixed via 'ebfa440ce38b vfio/pci: Fix
SR-IOV VF handling with MMIO blocking' which removes the
PCI_COMMAND_MEMORY requirement for VFs but this did not solve
the issue for virtual functions on s390 that are first passed
through to an LPAR without their associated physical function
as they are not identified as VFs in the traditional sense
(there is no PF available to the host kernel to link to). As a
result, when passing these devices through to a guest via
vfio-pci, these devices do not trigger the check added by
ebfa440ce38b which results in MMIO access from the guest being
blocked because the PCI_COMMAND_MEMORY bit is off.
Solution: Identify devices beyond traditional linked VFs that vfio must
consider memory-enabled.
Reproduction: Pass a PCI Virtual Function to a qemu-kvm guest via vfio-pci
Upstream-ID: 12856e7acde4702b7c3238c15fcba86ff6aa507f
08b6e22b850c28b6032da1e4d767a33116e23dfb
515ecd5368f1510152fa4f9b9ce55b66ac56c334
These patches need to be applied for 20.10 and 20.04.
The git-commits will apply cleanly on the dedicated kernels.
Manx thx
** Affects: linux (Ubuntu)
Importance: Undecided
Assignee: Skipper Bug Screeners (skipper-screen-team)
Status: New
** Tags: architecture-s39064 bugnameltc-190039 severity-high
targetmilestone-inin---
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[UBUNTU 21.04] s390/pci: vfio-pci mmio being disabled erroneously
https://bugs.launchpad.net/bugs/1907265
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