Summary edit
> KVM: arm/arm64: Require VCPU threads to turn them self off
themselves
On Fri, Jan 25, 2019 at 10:46:54AM +0100, Christoffer Dall wrote:
> To avoid a race between turning VCPUs off and turning them on, make sure
> that only the VCPU threat itself turns off the VCPU. When other threads
> want to turn of a VCPU, they now do this via a request.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxx>
> Acked-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> arch/arm/include/asm/kvm_host.h | 2 ++
> arch/arm64/include/asm/kvm_host.h | 2 ++
> virt/kvm/arm/arm.c | 8 ++++++--
> virt/kvm/arm/psci.c | 11 ++---------
> 4 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 50e89869178a..b1cfae222441 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -49,6 +49,8 @@
> KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
> #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1)
> #define KVM_REQ_VCPU_RESET KVM_ARCH_REQ(2)
> +#define KVM_REQ_VCPU_OFF \
> + KVM_ARCH_REQ_FLAGS(3, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
>
> DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index da3fc7324d68..d43b13421987 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -49,6 +49,8 @@
> KVM_ARCH_REQ_FLAGS(0, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
> #define KVM_REQ_IRQ_PENDING KVM_ARCH_REQ(1)
> #define KVM_REQ_VCPU_RESET KVM_ARCH_REQ(2)
> +#define KVM_REQ_VCPU_OFF \
> + KVM_ARCH_REQ_FLAGS(3, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
>
> DECLARE_STATIC_KEY_FALSE(userspace_irqchip_in_use);
>
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 9c486fad3f9f..785076176814 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -404,8 +404,7 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>
> static void vcpu_power_off(struct kvm_vcpu *vcpu)
> {
> - vcpu->arch.power_off = true;
> - kvm_make_request(KVM_REQ_SLEEP, vcpu);
> + kvm_make_request(KVM_REQ_VCPU_OFF, vcpu);
> kvm_vcpu_kick(vcpu);
> }
I think we should leave this function alone. Otherwise if userspace sets
the MP state to STOPPED and then queries the state before the vcpu
has a chance to manage its vcpu requests, the state will still indicate
RUNNBLE. The same goes for a query right after doing a vcpu init.
>
> @@ -646,6 +645,11 @@ static void check_vcpu_requests(struct kvm_vcpu *vcpu)
> if (kvm_check_request(KVM_REQ_SLEEP, vcpu))
> vcpu_req_sleep(vcpu);
>
> + if (kvm_check_request(KVM_REQ_VCPU_OFF, vcpu)) {
> + vcpu->arch.power_off = true;
> + vcpu_req_sleep(vcpu);
> + }
> +
> if (kvm_check_request(KVM_REQ_VCPU_RESET, vcpu))
> kvm_reset_vcpu(vcpu);
>
> diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
> index b9cff1d4b06d..20255319e193 100644
> --- a/virt/kvm/arm/psci.c
> +++ b/virt/kvm/arm/psci.c
> @@ -97,9 +97,7 @@ static unsigned long kvm_psci_vcpu_suspend(struct kvm_vcpu *vcpu)
>
> static void kvm_psci_vcpu_off(struct kvm_vcpu *vcpu)
> {
> - vcpu->arch.power_off = true;
> - kvm_make_request(KVM_REQ_SLEEP, vcpu);
> - kvm_vcpu_kick(vcpu);
> + kvm_make_request(KVM_REQ_VCPU_OFF, vcpu);
> }
This was currently fine since it implements CPU_OFF which only applies to
the calling vcpu, but there's also no reason not to change it to be
consistent with the below change
>
> static unsigned long kvm_psci_vcpu_on(struct kvm_vcpu *source_vcpu)
> @@ -198,9 +196,6 @@ static unsigned long kvm_psci_vcpu_affinity_info(struct kvm_vcpu *vcpu)
>
> static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
> {
> - int i;
> - struct kvm_vcpu *tmp;
> -
> /*
> * The KVM ABI specifies that a system event exit may call KVM_RUN
> * again and may perform shutdown/reboot at a later time that when the
> @@ -210,9 +205,7 @@ static void kvm_prepare_system_event(struct kvm_vcpu *vcpu, u32 type)
> * after this call is handled and before the VCPUs have been
> * re-initialized.
> */
> - kvm_for_each_vcpu(i, tmp, vcpu->kvm)
> - tmp->arch.power_off = true;
> - kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_SLEEP);
> + kvm_make_all_cpus_request(vcpu->kvm, KVM_REQ_VCPU_OFF);
>
> memset(&vcpu->run->system_event, 0, sizeof(vcpu->run->system_event));
> vcpu->run->system_event.type = type;
> --
> 2.18.0
>
Thanks,
drew
