[PATCH v2 00/10] vITS Migration fixes and reset

Eric Auger
2017-09-27T13:28:50Z

This series fixes various bugs observed when saving/restoring the
ITS state before the guest writes the ITS registers (on first boot or
after reset/reboot).

This is a follow up of Wanghaibin's series [1] plus additional
patches following additional code review. It also proposes one
ITS reset implementation. I dared to include 2 Wanghaibin patches,
taking into account the discussions held on the ML but obviously
they can live separately.

Currently, the in-kernel emulated ITS is not reset. After a
reset/reboot, the ITS register values and caches are left
unchanged. Registers may point to some tables in guest memory
which do not exist anymore. If an ITS state backup is initiated
before the guest re-writes the registers, the save fails
because inconsistencies are detected. Also restore of data saved
as such moment is failing.

Patches [1-6] attempt to fix the migration issues without
implementing the reset.
As such they may be candidate for stable:
- do not fail restore if device or ITT tables only contain invalid
entries
- allow clearing GITS_CREADR/CWRITER whatever CBASER queue size
- limit the cases where we return -EINVAL in table save()
- never attempt to use GITS_BASER<n> and GITS_CBASER if they are
not valid.
- systematically do both device and collection save/restore even if
one fails.

Patches [7-10] implement a new ITS reset IOCTL
- maybe patch "free caches when GITS_BASER Valid bit is cleared" can
be omitted if we consider the caches should not be cleared when
GITS_BASER<n>.Valid is cleared.

Best Regards

Eric

Git: complete series available at
https://github.com/eauger/linux/tree/v4.14-rc2-its-reset-v2

* Testing:
- on Cavium using a virtio-net-pci guest and various sequences of
guest shutdown -r now, virsh reset, virsh suspend/resume,
virsh reboot, virsh save.restore, virsh shutdown

References:
[1] [RFC PATCH 0/3] fix migrate failed when vm is in booting
https://www.spinics.net/lists/kvm-arm/msg27121.html

History:
v1 -> v2:
- added KVM: arm/arm64: vgic-its: Always attempt to save/restore
device and collection tables

PATCH v1
- series including 2 modified patches of Wanghaibin

Eric Auger (8):
KVM: arm/arm64: vgic-its: Always allow clearing GITS_CREADR/CWRITER
KVM: arm/arm64: vgic-its: Improve error reporting on device table save
KVM: arm/arm64: vgic-its: Check GITS_BASER Valid bit before saving
tables
KVM: arm/arm64: vgic-its: Check GITS_CBASER validity before processing
commands
KVM: arm/arm64: vgic-its: Always attempt to save/restore device and
collection tables
KVM: arm/arm64: vgic-its: free caches when GITS_BASER Valid bit is
cleared
KVM: arm/arm64: Document KVM_DEV_ARM_ITS_CTRL_RESET
KVM: arm/arm64: vgic-its: Implement KVM_DEV_ARM_ITS_CTRL_RESET

wanghaibin (2):
KVM: arm/arm64: vgic-its: fix return value for restore
KVM: arm/arm64: vgic-its: new helper functions to free the caches

Documentation/virtual/kvm/devices/arm-vgic-its.txt | 16 ++
arch/arm/include/uapi/asm/kvm.h | 1 +
arch/arm64/include/uapi/asm/kvm.h | 1 +
virt/kvm/arm/vgic/vgic-its.c | 222 +++++++++++++--------
4 files changed, 158 insertions(+), 82 deletions(-)

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2.5.5