[v2,0/4] KVM: arm64: Fix vcpu->mutex v. kvm->lock inversion

Message

Oliver Upton March 16, 2023, 9:14 p.m. UTC

As it so happens, lock ordering in KVM/arm64 is completely backwards.
There's a significant amount of VM-wide state that needs to be accessed
from the context of a vCPU. Until now, this was accomplished by
acquiring the kvm->lock, but that cannot be nested within vcpu->mutex.

This series fixes the issue with some fine-grained locking for MP state
and a new, dedicated mutex that can nest with both kvm->lock and
vcpu->mutex.

Tested with kvmtool and QEMU scaled up to 64 vCPUs on a kernel w/
lockdep enabled. Applies to kvmarm/next.

v1: http://lore.kernel.org/kvmarm/[e-mail]

v1 -> v2:
 - Add a dedicated lock for serializing writes to MP state
 - Inform lockdep of acquisition order at time of VM/vCPU creation
 - Plug a race with GIC creation (Sean)
 - Use the config_lock in GIC ITS flows as well. There is now a single
   (valid) use of kvm->lock when enabling MTE.

Oliver Upton (4):
  KVM: arm64: Avoid vcpu->mutex v. kvm->lock inversion in CPU_ON
  KVM: arm64: Avoid lock inversion when setting the VM register width
  KVM: arm64: Use config_lock to protect data ordered against KVM_RUN
  KVM: arm64: Use config_lock to protect vgic state

 arch/arm64/include/asm/kvm_host.h     |  4 ++
 arch/arm64/kvm/arm.c                  | 45 +++++++++++++++++++----
 arch/arm64/kvm/guest.c                |  2 +
 arch/arm64/kvm/hypercalls.c           |  4 +-
 arch/arm64/kvm/pmu-emul.c             | 23 +++---------
 arch/arm64/kvm/psci.c                 | 19 +++++-----
 arch/arm64/kvm/reset.c                | 16 ++++----
 arch/arm64/kvm/vgic/vgic-debug.c      |  8 ++--
 arch/arm64/kvm/vgic/vgic-init.c       | 33 ++++++++++-------
 arch/arm64/kvm/vgic/vgic-its.c        | 29 ++++++---------
 arch/arm64/kvm/vgic/vgic-kvm-device.c | 53 ++++++++++++---------------
 arch/arm64/kvm/vgic/vgic-mmio-v3.c    |  4 +-
 arch/arm64/kvm/vgic/vgic-mmio.c       | 12 +++---
 arch/arm64/kvm/vgic/vgic-v4.c         | 11 +++---
 arch/arm64/kvm/vgic/vgic.c            |  2 +-
 15 files changed, 146 insertions(+), 119 deletions(-)

Comments

Jeremy Linton March 23, 2023, 10:48 p.m. UTC | #1

Hi,

On 3/16/23 16:14, Oliver Upton wrote:
> As it so happens, lock ordering in KVM/arm64 is completely backwards.
> There's a significant amount of VM-wide state that needs to be accessed
> from the context of a vCPU. Until now, this was accomplished by
> acquiring the kvm->lock, but that cannot be nested within vcpu->mutex.
> 
> This series fixes the issue with some fine-grained locking for MP state
> and a new, dedicated mutex that can nest with both kvm->lock and
> vcpu->mutex.
> 
> Tested with kvmtool and QEMU scaled up to 64 vCPUs on a kernel w/
> lockdep enabled. Applies to kvmarm/next.

This set makes the reported lockdep error go away for me, it also 
appears to complete some basic kernel/kvm testing without error as well. So,

Tested-by: Jeremy Linton <[e-mail]>


Thanks,

> 
> v1: http://lore.kernel.org/kvmarm/[e-mail]
> 
> v1 -> v2:
>   - Add a dedicated lock for serializing writes to MP state
>   - Inform lockdep of acquisition order at time of VM/vCPU creation
>   - Plug a race with GIC creation (Sean)
>   - Use the config_lock in GIC ITS flows as well. There is now a single
>     (valid) use of kvm->lock when enabling MTE.
> 
> Oliver Upton (4):
>    KVM: arm64: Avoid vcpu->mutex v. kvm->lock inversion in CPU_ON
>    KVM: arm64: Avoid lock inversion when setting the VM register width
>    KVM: arm64: Use config_lock to protect data ordered against KVM_RUN
>    KVM: arm64: Use config_lock to protect vgic state
> 
>   arch/arm64/include/asm/kvm_host.h     |  4 ++
>   arch/arm64/kvm/arm.c                  | 45 +++++++++++++++++++----
>   arch/arm64/kvm/guest.c                |  2 +
>   arch/arm64/kvm/hypercalls.c           |  4 +-
>   arch/arm64/kvm/pmu-emul.c             | 23 +++---------
>   arch/arm64/kvm/psci.c                 | 19 +++++-----
>   arch/arm64/kvm/reset.c                | 16 ++++----
>   arch/arm64/kvm/vgic/vgic-debug.c      |  8 ++--
>   arch/arm64/kvm/vgic/vgic-init.c       | 33 ++++++++++-------
>   arch/arm64/kvm/vgic/vgic-its.c        | 29 ++++++---------
>   arch/arm64/kvm/vgic/vgic-kvm-device.c | 53 ++++++++++++---------------
>   arch/arm64/kvm/vgic/vgic-mmio-v3.c    |  4 +-
>   arch/arm64/kvm/vgic/vgic-mmio.c       | 12 +++---
>   arch/arm64/kvm/vgic/vgic-v4.c         | 11 +++---
>   arch/arm64/kvm/vgic/vgic.c            |  2 +-
>   15 files changed, 146 insertions(+), 119 deletions(-)
>