[PATCH v3 1/2] KVM: arm/arm64: Add save/restore support for firmware workaround state

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On 22/02/2019 12:18, Andre Przywara wrote:
> KVM implements the firmware interface for mitigating cache speculation
> vulnerabilities. Guests may use this interface to ensure mitigation is
> active.
> If we want to migrate such a guest to a host with a different support
> level for those workarounds, migration might need to fail, to ensure that
> critical guests don't loose their protection.
> 
> Introduce a way for userland to save and restore the workarounds state.
> On restoring we do checks that make sure we don't downgrade our
> mitigation level.
> 
> Signed-off-by: Andre Przywara <andre.przywara at arm.com>
> ---
>  arch/arm/include/asm/kvm_emulate.h   |  10 +++
>  arch/arm/include/uapi/asm/kvm.h      |  10 +++
>  arch/arm64/include/asm/kvm_emulate.h |  14 ++++
>  arch/arm64/include/uapi/asm/kvm.h    |   9 ++
>  virt/kvm/arm/psci.c                  | 119 +++++++++++++++++++++++----
>  5 files changed, 146 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> index 8927cae7c966..663a02d7e6f4 100644
> --- a/arch/arm/include/asm/kvm_emulate.h
> +++ b/arch/arm/include/asm/kvm_emulate.h
> @@ -283,6 +283,16 @@ static inline unsigned long kvm_vcpu_get_mpidr_aff(struct kvm_vcpu *vcpu)
>  	return vcpu_cp15(vcpu, c0_MPIDR) & MPIDR_HWID_BITMASK;
>  }
>  
> +static inline bool kvm_arm_get_vcpu_workaround_2_flag(struct kvm_vcpu *vcpu)
> +{
> +	return false;
> +}
> +
> +static inline void kvm_arm_set_vcpu_workaround_2_flag(struct kvm_vcpu *vcpu,
> +						      bool flag)
> +{
> +}
> +
>  static inline void kvm_vcpu_set_be(struct kvm_vcpu *vcpu)
>  {
>  	*vcpu_cpsr(vcpu) |= PSR_E_BIT;
> diff --git a/arch/arm/include/uapi/asm/kvm.h b/arch/arm/include/uapi/asm/kvm.h
> index 4602464ebdfb..ba4d2afe65e3 100644
> --- a/arch/arm/include/uapi/asm/kvm.h
> +++ b/arch/arm/include/uapi/asm/kvm.h
> @@ -214,6 +214,16 @@ struct kvm_vcpu_events {
>  #define KVM_REG_ARM_FW_REG(r)		(KVM_REG_ARM | KVM_REG_SIZE_U64 | \
>  					 KVM_REG_ARM_FW | ((r) & 0xffff))
>  #define KVM_REG_ARM_PSCI_VERSION	KVM_REG_ARM_FW_REG(0)
> +#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1	KVM_REG_ARM_FW_REG(1)
> +#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_NOT_AVAIL	0
> +#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_AVAIL	1
> +#define KVM_REG_ARM_SMCCC_ARCH_WORKAROUND_1_UNAFFECTED	2

Thanks for adding the UNAFFECTED state for WORKAROUND_1 - this means the
ABI at least can deal with migration to a host which supports but
doesn't need the workaround. I'm happy for the actual support for this
to be added later if/when it's needed.

Reviewed-by: Steven Price <steven.price at arm.com>


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