Hi Will,
> -----Original Message-----
> From: Jianyong Wu <jianyong.wu@xxxxxxx>
> Sent: Friday, June 19, 2020 9:01 PM
> To: netdev@xxxxxxxxxxxxxxx; yangbo.lu@xxxxxxx; john.stultz@xxxxxxxxxx;
> tglx@xxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; sean.j.christopherson@xxxxxxxxx;
> maz@xxxxxxxxxx; richardcochran@xxxxxxxxx; Mark Rutland
> <Mark.Rutland@xxxxxxx>; will@xxxxxxxxxx; Suzuki Poulose
> <Suzuki.Poulose@xxxxxxx>; Steven Price <Steven.Price@xxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx; linux-arm-kernel@xxxxxxxxxxxxxxxxxxx;
> kvmarm@xxxxxxxxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Steve Capper
> <Steve.Capper@xxxxxxx>; Kaly Xin <Kaly.Xin@xxxxxxx>; Justin He
> <Justin.He@xxxxxxx>; Wei Chen <Wei.Chen@xxxxxxx>; Jianyong Wu
> <Jianyong.Wu@xxxxxxx>; nd <nd@xxxxxxx>
> Subject: [PATCH v13 2/9] arm/arm64: KVM: Advertise KVM UID to guests via
> SMCCC
>
> From: Will Deacon <will@xxxxxxxxxx>
>
> We can advertise ourselves to guests as KVM and provide a basic features
> bitmap for discoverability of future hypervisor services.
>
> Cc: Marc Zyngier <maz@xxxxxxxxxx>
> Signed-off-by: Will Deacon <will@xxxxxxxxxx>
> Signed-off-by: Jianyong Wu <jianyong.wu@xxxxxxx>
> ---
> arch/arm64/kvm/hypercalls.c | 29 +++++++++++++++++++----------
> 1 file changed, 19 insertions(+), 10 deletions(-)
>
> diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
> index 550dfa3e53cd..db6dce3d0e23 100644
> --- a/arch/arm64/kvm/hypercalls.c
> +++ b/arch/arm64/kvm/hypercalls.c
> @@ -12,13 +12,13 @@
> int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) {
> u32 func_id = smccc_get_function(vcpu);
> - long val = SMCCC_RET_NOT_SUPPORTED;
> + u32 val[4] = {SMCCC_RET_NOT_SUPPORTED};
There is a risk as this u32 value will return here and a u64 value will be obtained in guest. For example,
The val[0] is initialized as -1 of 0xffffffff and the guest get 0xffffffff then it will be compared with -1 of 0xffffffffffffffff
Also this problem exists for the transfer of address in u64 type. So the following assignment to "val" should be split into
two u32 value and assign to val[0] and val[1] respectively.
WDYT?
Thanks
Jianyong
> u32 feature;
> gpa_t gpa;
>
> switch (func_id) {
> case ARM_SMCCC_VERSION_FUNC_ID:
> - val = ARM_SMCCC_VERSION_1_1;
> + val[0] = ARM_SMCCC_VERSION_1_1;
> break;
> case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
> feature = smccc_get_arg1(vcpu);
> @@ -28,10 +28,10 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
> case KVM_BP_HARDEN_UNKNOWN:
> break;
> case KVM_BP_HARDEN_WA_NEEDED:
> - val = SMCCC_RET_SUCCESS;
> + val[0] = SMCCC_RET_SUCCESS;
> break;
> case KVM_BP_HARDEN_NOT_REQUIRED:
> - val = SMCCC_RET_NOT_REQUIRED;
> + val[0] = SMCCC_RET_NOT_REQUIRED;
> break;
> }
> break;
> @@ -41,31 +41,40 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
> case KVM_SSBD_UNKNOWN:
> break;
> case KVM_SSBD_KERNEL:
> - val = SMCCC_RET_SUCCESS;
> + val[0] = SMCCC_RET_SUCCESS;
> break;
> case KVM_SSBD_FORCE_ENABLE:
> case KVM_SSBD_MITIGATED:
> - val = SMCCC_RET_NOT_REQUIRED;
> + val[0] = SMCCC_RET_NOT_REQUIRED;
> break;
> }
> break;
> case ARM_SMCCC_HV_PV_TIME_FEATURES:
> - val = SMCCC_RET_SUCCESS;
> + val[0] = SMCCC_RET_SUCCESS;
> break;
> }
> break;
> case ARM_SMCCC_HV_PV_TIME_FEATURES:
> - val = kvm_hypercall_pv_features(vcpu);
> + val[0] = kvm_hypercall_pv_features(vcpu);
> break;
> case ARM_SMCCC_HV_PV_TIME_ST:
> gpa = kvm_init_stolen_time(vcpu);
> if (gpa != GPA_INVALID)
> - val = gpa;
> + val[0] = gpa;
> + break;
> + case ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID:
> + val[0] = ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_0;
> + val[1] = ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_1;
> + val[2] = ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2;
> + val[3] = ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3;
> + break;
> + case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
> + val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
> break;
> default:
> return kvm_psci_call(vcpu);
> }
>
> - smccc_set_retval(vcpu, val, 0, 0, 0);
> + smccc_set_retval(vcpu, val[0], val[1], val[2], val[3]);
> return 1;
> }
> --
> 2.17.1
