Il 17/12/2013 19:57, Jan Kiszka ha scritto:
> When userspace sets MSR_IA32_FEATURE_CONTROL to 0, make sure we leave
> root and non-root mode, fully disabling VMX. The register state of the
> VCPU is undefined after this step, so userspace has to set it to a
> proper state afterward.
>
> This enables to reboot a VM while it is running some hypervisor code.
>
> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
> ---
>
> Even without a QEMU patch, this already enables system reset - the guest
> is left in such a broken state that it simply triple-faults and resets
> twice. Nevertheless, QEMU patch will follow.
>
> arch/x86/kvm/vmx.c | 14 ++++++++++++++
> 1 file changed, 14 insertions(+)
>
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index f90320b..6a0c2fa 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2455,6 +2455,8 @@ static int vmx_get_vmx_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 *pdata)
> return 1;
> }
>
> +static void vmx_leave_nested(struct kvm_vcpu *vcpu);
> +
> static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> {
> u32 msr_index = msr_info->index;
> @@ -2470,6 +2472,8 @@ static int vmx_set_vmx_msr(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
> & FEATURE_CONTROL_LOCKED)
> return 0;
> to_vmx(vcpu)->nested.msr_ia32_feature_control = data;
> + if (host_initialized && data == 0)
> + vmx_leave_nested(vcpu);
> return 1;
> }
>
> @@ -8488,6 +8492,16 @@ static void nested_vmx_vmexit(struct kvm_vcpu *vcpu)
> }
>
> /*
> + * Forcibly leave nested mode in order to be able to reset the VCPU later on.
> + */
> +static void vmx_leave_nested(struct kvm_vcpu *vcpu)
> +{
> + if (is_guest_mode(vcpu))
> + nested_vmx_vmexit(vcpu);
> + free_nested(to_vmx(vcpu));
> +}
> +
> +/*
> * L1's failure to enter L2 is a subset of a normal exit, as explained in
> * 23.7 "VM-entry failures during or after loading guest state" (this also
> * lists the acceptable exit-reason and exit-qualification parameters).
>
Applied, thanks!
Paolo
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