[PATCH v2 0/6] Improve PSCI system events and fix reboot bugs

[Christoffer Dall]

Several people have reported problems with rebooting ARM VMs, especially
on 32-bit ARM.  This is mainly due to the same reason we were seeing
boot errors in the past, namely that the ram, dcache, and icache weren't
coherent on guest boot with the guest (stage-1) MMU disabled.  We solved
this by ensuring coherency when we fault in pages, but since most memory
is already mapped after a reboot, we don't do anything.

The solution is to unmap the regular RAM on VCPU init, but we must
take care to not unmap the GIC or other IO regions, hence the somehwat
complicated solution.

As part of figuring this out, it became clear that some semantics around
the KVM_ARM_VCPU_INIT ABI and system event ABI was unclear (what is
userspace expected to do when it receives a system event).  This series
also clarifies the ABI and changes the kernel functionality to do what
userspace expects (turn off VCPUs on a system shutdown event).

The code is avaliable here as well:
http://git.linaro.org/people/christoffer.dall/linux-kvm-arm.git vcpu_init_fixes-v2

There is an alternative version with more code-reuse for the unmapping
implementation for the previous version of this patch series available
in the following git repo:

http://git.linaro.org/people/christoffer.dall/linux-kvm-arm.git vcpu_init_fixes-alternative

Testing
-------
This has been tested on CubieBoard, Arndale, TC2, and Juno.  On Arndale
and TC2 it was extremely easy to reproduce the problem (just start a VM
that runs reboot from /etc/rc.local or similar) and this series clearly
fixes the behavior.  For the previous version of this series, I was
seeing some problems on Juno, but it turned out to be because I wasn't
limiting my testing to one of the clusters, and since we don't support
re-initing a VCPU on a different physical host CPU (big.LITTLE), it was
failing.  For this version of the patch series, it has been running a
reboot loop on Juno for hours.

Changelog
---------
Changes v1->v2:
 - New patch to not clear the VCPU_POWER_OFF flag
 - Fixed spelling error in commit message
 - Adapted ABI texts based on Peter's feedback
 - Check for changed parameters to KVM_ARM_VCPU_INIT
 - Now unmap the Stage-2 RAM mappings at VCPU init instead of at PSCI
   system event time.

Christoffer Dall (6):
  arm/arm64: KVM: Don't clear the VCPU_POWER_OFF flag
  arm/arm64: KVM: Correct KVM_ARM_VCPU_INIT power off option
  arm/arm64: KVM: Reset the HCR on each vcpu when resetting the vcpu
  arm/arm64: KVM: Clarify KVM_ARM_VCPU_INIT ABI
  arm/arm64: KVM: Turn off vcpus on PSCI shutdown/reboot
  arm/arm64: KVM: Introduce stage2_unmap_vm

 Documentation/virtual/kvm/api.txt    | 17 +++++++++-
 arch/arm/include/asm/kvm_emulate.h   |  5 +++
 arch/arm/include/asm/kvm_host.h      |  2 --
 arch/arm/include/asm/kvm_mmu.h       |  1 +
 arch/arm/kvm/arm.c                   | 56 ++++++++++++++++++++++++++++++-
 arch/arm/kvm/guest.c                 | 26 ---------------
 arch/arm/kvm/mmu.c                   | 65 ++++++++++++++++++++++++++++++++++++
 arch/arm/kvm/psci.c                  | 19 +++++++++++
 arch/arm64/include/asm/kvm_emulate.h |  5 +++
 arch/arm64/include/asm/kvm_host.h    |  3 +-
 arch/arm64/include/asm/kvm_mmu.h     |  1 +
 arch/arm64/kvm/guest.c               | 26 ---------------
 12 files changed, 168 insertions(+), 58 deletions(-)

-- 
2.1.2.330.g565301e.dirty