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Subject: Re: [PATCH v2 3/6] KVM: arm64: Support pvlock preempted via shared
 structure
To:     Zengruan Ye <yezengruan@huawei.com>, linux-kernel@vger.kernel.org,
        linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu,
        kvm@vger.kernel.org, linux-doc@vger.kernel.org,
        virtualization@lists.linux-foundation.org
Cc:     maz@kernel.org, james.morse@arm.com, linux@armlinux.org.uk,
        suzuki.poulose@arm.com, julien.thierry.kdev@gmail.com,
        catalin.marinas@arm.com, mark.rutland@arm.com, will@kernel.org,
        daniel.lezcano@linaro.org
References: <20191226135833.1052-1-yezengruan@huawei.com>
 <20191226135833.1052-4-yezengruan@huawei.com>
From:   Steven Price <steven.price@arm.com>
Message-ID: <468e2bb4-8986-5e1e-8c4a-31aa56a9ae4f@arm.com>
Date:   Thu, 9 Jan 2020 15:02:07 +0000
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On 26/12/2019 13:58, Zengruan Ye wrote:
> Implement the service call for configuring a shared structure between a
> VCPU and the hypervisor in which the hypervisor can tell the VCPU is
> running or not.
> 
> The preempted field is zero if 1) some old KVM deos not support this filed.

NIT: s/deos/does/

However, I would hope that the service call will fail if it's an old KVM not simply return zero.

> 2) the VCPU is not preempted. Other values means the VCPU has been preempted.
> 
> Signed-off-by: Zengruan Ye <yezengruan@huawei.com>
> ---
>   arch/arm/include/asm/kvm_host.h   | 18 ++++++++++++
>   arch/arm64/include/asm/kvm_host.h | 19 +++++++++++++
>   arch/arm64/kvm/Makefile           |  1 +
>   virt/kvm/arm/arm.c                |  8 ++++++
>   virt/kvm/arm/hypercalls.c         |  8 ++++++
>   virt/kvm/arm/pvlock.c             | 46 +++++++++++++++++++++++++++++++
>   6 files changed, 100 insertions(+)
>   create mode 100644 virt/kvm/arm/pvlock.c
> 
> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
> index 556cd818eccf..dfeaf9204875 100644
> --- a/arch/arm/include/asm/kvm_host.h
> +++ b/arch/arm/include/asm/kvm_host.h
> @@ -356,6 +356,24 @@ static inline bool kvm_arm_is_pvtime_enabled(struct kvm_vcpu_arch *vcpu_arch)
>   	return false;
>   }
>   
> +static inline void kvm_arm_pvlock_preempted_init(struct kvm_vcpu_arch *vcpu_arch)
> +{
> +}
> +
> +static inline bool kvm_arm_is_pvlock_preempted_ready(struct kvm_vcpu_arch *vcpu_arch)
> +{
> +	return false;
> +}
> +
> +static inline gpa_t kvm_init_pvlock(struct kvm_vcpu *vcpu)
> +{
> +	return GPA_INVALID;
> +}
> +
> +static inline void kvm_update_pvlock_preempted(struct kvm_vcpu *vcpu, u64 preempted)
> +{
> +}
> +
>   void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>   
>   struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index c61260cf63c5..2818a2330f92 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -354,6 +354,12 @@ struct kvm_vcpu_arch {
>   		u64 last_steal;
>   		gpa_t base;
>   	} steal;
> +
> +	/* Guest PV lock state */
> +	struct {
> +		u64 preempted;

I'm not sure why the kernel needs to (separately) track this preempted state? It doesn't appear to be used from what I can tell.

Steve

> +		gpa_t base;
> +	} pv;
>   };
>   
>   /* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
> @@ -515,6 +521,19 @@ static inline bool kvm_arm_is_pvtime_enabled(struct kvm_vcpu_arch *vcpu_arch)
>   	return (vcpu_arch->steal.base != GPA_INVALID);
>   }
>   
> +static inline void kvm_arm_pvlock_preempted_init(struct kvm_vcpu_arch *vcpu_arch)
> +{
> +	vcpu_arch->pv.base = GPA_INVALID;
> +}
> +
> +static inline bool kvm_arm_is_pvlock_preempted_ready(struct kvm_vcpu_arch *vcpu_arch)
> +{
> +	return (vcpu_arch->pv.base != GPA_INVALID);
> +}
> +
> +gpa_t kvm_init_pvlock(struct kvm_vcpu *vcpu);
> +void kvm_update_pvlock_preempted(struct kvm_vcpu *vcpu, u64 preempted);
> +
>   void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
>   
>   struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
> index 5ffbdc39e780..e4591f56d5f1 100644
> --- a/arch/arm64/kvm/Makefile
> +++ b/arch/arm64/kvm/Makefile
> @@ -15,6 +15,7 @@ kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/arm.o $(KVM)/arm/mmu.o $(KVM)/arm/mmio.
>   kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/psci.o $(KVM)/arm/perf.o
>   kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/hypercalls.o
>   kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvtime.o
> +kvm-$(CONFIG_KVM_ARM_HOST) += $(KVM)/arm/pvlock.o
>   
>   kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o va_layout.o
>   kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
> diff --git a/virt/kvm/arm/arm.c b/virt/kvm/arm/arm.c
> index 8de4daf25097..36d57e77d3c4 100644
> --- a/virt/kvm/arm/arm.c
> +++ b/virt/kvm/arm/arm.c
> @@ -383,6 +383,8 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
>   
>   	kvm_arm_pvtime_vcpu_init(&vcpu->arch);
>   
> +	kvm_arm_pvlock_preempted_init(&vcpu->arch);
> +
>   	return kvm_vgic_vcpu_init(vcpu);
>   }
>   
> @@ -421,6 +423,9 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>   		vcpu_set_wfx_traps(vcpu);
>   
>   	vcpu_ptrauth_setup_lazy(vcpu);
> +
> +	if (kvm_arm_is_pvlock_preempted_ready(&vcpu->arch))
> +		kvm_update_pvlock_preempted(vcpu, 0);
>   }
>   
>   void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
> @@ -434,6 +439,9 @@ void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>   	vcpu->cpu = -1;
>   
>   	kvm_arm_set_running_vcpu(NULL);
> +
> +	if (kvm_arm_is_pvlock_preempted_ready(&vcpu->arch))
> +		kvm_update_pvlock_preempted(vcpu, 1);
>   }
>   
>   static void vcpu_power_off(struct kvm_vcpu *vcpu)
> diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
> index 550dfa3e53cd..1c6a11f21bb4 100644
> --- a/virt/kvm/arm/hypercalls.c
> +++ b/virt/kvm/arm/hypercalls.c
> @@ -52,6 +52,9 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>   		case ARM_SMCCC_HV_PV_TIME_FEATURES:
>   			val = SMCCC_RET_SUCCESS;
>   			break;
> +		case ARM_SMCCC_HV_PV_LOCK_FEATURES:
> +			val = SMCCC_RET_SUCCESS;
> +			break;
>   		}
>   		break;
>   	case ARM_SMCCC_HV_PV_TIME_FEATURES:
> @@ -62,6 +65,11 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
>   		if (gpa != GPA_INVALID)
>   			val = gpa;
>   		break;
> +	case ARM_SMCCC_HV_PV_LOCK_PREEMPTED:
> +		gpa = kvm_init_pvlock(vcpu);
> +		if (gpa != GPA_INVALID)
> +			val = gpa;
> +		break;
>   	default:
>   		return kvm_psci_call(vcpu);
>   	}
> diff --git a/virt/kvm/arm/pvlock.c b/virt/kvm/arm/pvlock.c
> new file mode 100644
> index 000000000000..cdfd30a903b9
> --- /dev/null
> +++ b/virt/kvm/arm/pvlock.c
> @@ -0,0 +1,46 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +/*
> + * Copyright(c) 2019 Huawei Technologies Co., Ltd
> + * Author: Zengruan Ye <yezengruan@huawei.com>
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/kvm_host.h>
> +
> +#include <asm/pvlock-abi.h>
> +
> +#include <kvm/arm_hypercalls.h>
> +
> +gpa_t kvm_init_pvlock(struct kvm_vcpu *vcpu)
> +{
> +	struct pvlock_vcpu_state init_values = {};
> +	struct kvm *kvm = vcpu->kvm;
> +	u64 base = vcpu->arch.pv.base;
> +	int idx;
> +
> +	if (base == GPA_INVALID)
> +		return base;
> +
> +	idx = srcu_read_lock(&kvm->srcu);
> +	kvm_write_guest(kvm, base, &init_values, sizeof(init_values));
> +	srcu_read_unlock(&kvm->srcu, idx);
> +
> +	return base;
> +}
> +
> +void kvm_update_pvlock_preempted(struct kvm_vcpu *vcpu, u64 preempted)
> +{
> +	int idx;
> +	u64 offset;
> +	__le64 preempted_le;
> +	struct kvm *kvm = vcpu->kvm;
> +	u64 base = vcpu->arch.pv.base;
> +
> +	vcpu->arch.pv.preempted = preempted;
> +	preempted_le = cpu_to_le64(preempted);
> +
> +	idx = srcu_read_lock(&kvm->srcu);
> +	offset = offsetof(struct pvlock_vcpu_state, preempted);
> +	kvm_put_guest(kvm, base + offset, preempted_le, u64);
> +	srcu_read_unlock(&kvm->srcu, idx);
> +}
>