On Wed, Aug 15, 2012 at 8:51 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> If a VM exits in the middle of an exclusive operation (ldrex/strex),
> it leaves the exclusive monitor in a state that can influence the host
> (specially if they all run the same kernel or userspace, as all the
> virtual addresses will be the same). Conversly, the host state can
> influence the guest in the same way.
>
> This has been observed on TC2 running two VMs with the same kernel as
> the host, and seeing deadlocks (or lockdep moaning about locks being
> already taken by another CPU).
>
> The fix is to clear the exclusive monitor on both exception return
> paths (which is consistent with what the kernel is doing for userspace)
> so that the different worlds are properly isolated.
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/kvm/interrupts.S | 2 ++
> 1 file changed, 2 insertions(+)
>
> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
> index 696d539..16ad354 100644
> --- a/arch/arm/kvm/interrupts.S
> +++ b/arch/arm/kvm/interrupts.S
> @@ -565,6 +565,7 @@ ENTRY(__kvm_vcpu_run)
> @ Load remaining registers and do the switch
> sub r0, r0, #(VCPU_PC - VCPU_USR_REGS)
> ldmia r0, {r0-r12}
> + clrex @ Clear exclusive monitor
> eret
>
> __kvm_vcpu_return:
> @@ -641,6 +642,7 @@ after_vfp_restore:
>
> hvc #0 @ switch back to svc-mode, see hyp_svc
>
> + clrex @ Clear exclusive monitor
> bx lr @ return to IOCTL
>
> @@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
> --
> 1.7.10.3
>
damn, missed these for v10.
this one is applied to v11-stage.
thanks.
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