Re: [PATCH 23/59] KVM: arm64: nv: Respect virtual HCR_EL2.TWX setting

Julien Thierry
2019-06-25T14:19:38Z

On 06/21/2019 10:38 AM, Marc Zyngier wrote:
> From: Jintack Lim <jintack.lim@linaro.org>
>
> Forward exceptions due to WFI or WFE instructions to the virtual EL2 if
> they are not coming from the virtual EL2 and virtual HCR_EL2.TWX is set.
>
> Signed-off-by: Jintack Lim <jintack.lim@linaro.org>
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> arch/arm64/include/asm/kvm_nested.h | 2 ++
> arch/arm64/kvm/Makefile | 1 +
> arch/arm64/kvm/handle_exit.c | 13 +++++++++-
> arch/arm64/kvm/nested.c | 39 +++++++++++++++++++++++++++++
> 4 files changed, 54 insertions(+), 1 deletion(-)
> create mode 100644 arch/arm64/kvm/nested.c
>
> diff --git a/arch/arm64/include/asm/kvm_nested.h b/arch/arm64/include/asm/kvm_nested.h
> index 8a3d121a0b42..645e5e11b749 100644
> --- a/arch/arm64/include/asm/kvm_nested.h
> +++ b/arch/arm64/include/asm/kvm_nested.h
> @@ -10,4 +10,6 @@ static inline bool nested_virt_in_use(const struct kvm_vcpu *vcpu)
> test_bit(KVM_ARM_VCPU_NESTED_VIRT, vcpu->arch.features);
> }
>
> +int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe);
> +
> #endif /* __ARM64_KVM_NESTED_H */
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 9e450aea7db6..f11bd8b0d837 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -36,4 +36,5 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/irqchip.o
> kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arch_timer.o
> kvm-$(CONFIG_KVM_ARM_PMU) += $(KVM)/arm/pmu.o
>
> +kvm-$(CONFIG_KVM_ARM_HOST) += nested.o
> kvm-$(CONFIG_KVM_ARM_HOST) += emulate-nested.o
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index e348c15c81bc..ddba212fd6ec 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -127,7 +127,18 @@ static int handle_no_fpsimd(struct kvm_vcpu *vcpu, struct kvm_run *run)
> */
> static int kvm_handle_wfx(struct kvm_vcpu *vcpu, struct kvm_run *run)
> {
> - if (kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE) {
> + bool is_wfe = !!(kvm_vcpu_get_hsr(vcpu) & ESR_ELx_WFx_ISS_WFE);
> +
> + if (nested_virt_in_use(vcpu)) {
> + int ret = handle_wfx_nested(vcpu, is_wfe);
> +
> + if (ret < 0 && ret != -EINVAL)
> + return ret;
> + else if (ret >= 0)
> + return ret;

I think you can simplify this:

if (ret != -EINVAL)
return ret;

Cheers,

Julien

> + }
> +
> + if (is_wfe) {
> trace_kvm_wfx_arm64(*vcpu_pc(vcpu), true);
> vcpu->stat.wfe_exit_stat++;
> kvm_vcpu_on_spin(vcpu, vcpu_mode_priv(vcpu));
> diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
> new file mode 100644
> index 000000000000..3872e3cf1691
> --- /dev/null
> +++ b/arch/arm64/kvm/nested.c
> @@ -0,0 +1,39 @@
> +/*
> + * Copyright (C) 2017 - Columbia University and Linaro Ltd.
> + * Author: Jintack Lim <jintack.lim@linaro.org>
> + *
> + * This program is free software; you can redistribute it and/or modify
> + * it under the terms of the GNU General Public License version 2 as
> + * published by the Free Software Foundation.
> + *
> + * This program is distributed in the hope that it will be useful,
> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
> + * GNU General Public License for more details.
> + *
> + * You should have received a copy of the GNU General Public License
> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
> + */
> +
> +#include <linux/kvm.h>
> +#include <linux/kvm_host.h>
> +
> +#include <asm/kvm_emulate.h>
> +
> +/*
> + * Inject wfx to the virtual EL2 if this is not from the virtual EL2 and
> + * the virtual HCR_EL2.TWX is set. Otherwise, let the host hypervisor
> + * handle this.
> + */
> +int handle_wfx_nested(struct kvm_vcpu *vcpu, bool is_wfe)
> +{
> + u64 hcr_el2 = __vcpu_sys_reg(vcpu, HCR_EL2);
> +
> + if (vcpu_mode_el2(vcpu))
> + return -EINVAL;
> +
> + if ((is_wfe && (hcr_el2 & HCR_TWE)) || (!is_wfe && (hcr_el2 & HCR_TWI)))
> + return kvm_inject_nested_sync(vcpu, kvm_vcpu_get_hsr(vcpu));
> +
> + return -EINVAL;
> +}