[v17,6/7] KVM: arm64: Add support for the KVM PTP service

Message ID	20210202141204.3134855-7-maz@kernel.org (mailing list archive)
State	Superseded
Headers	show Return-Path: <netdev-owner@kernel.org> From: Marc Zyngier <maz@kernel.org> To: netdev@vger.kernel.org, yangbo.lu@nxp.com, john.stultz@linaro.org, tglx@linutronix.de, pbonzini@redhat.com, seanjc@google.com, richardcochran@gmail.com, Mark.Rutland@arm.com, will@kernel.org, suzuki.poulose@arm.com, Andre.Przywara@arm.com, steven.price@arm.com Cc: linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org, Steve.Capper@arm.com, justin.he@arm.com, jianyong.wu@arm.com, kernel-team@android.com Subject: [PATCH v17 6/7] KVM: arm64: Add support for the KVM PTP service Date: Tue, 2 Feb 2021 14:12:03 +0000 Message-Id: <20210202141204.3134855-7-maz@kernel.org> In-Reply-To: <20210202141204.3134855-1-maz@kernel.org> References: <20210202141204.3134855-1-maz@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	KVM: arm64: Add host/guest KVM-PTP support \| expand [v17,0/7] KVM: arm64: Add host/guest KVM-PTP support [v17,1/7] arm/arm64: Probe for the presence of KVM hypervisor [v17,2/7] KVM: arm64: Advertise KVM UID to guests via SMCCC [v17,3/7] ptp: Reorganize ptp_kvm.c to make it arch-independent [v17,4/7] time: Add mechanism to recognize clocksource in time_get_snapshot [v17,5/7] clocksource: Add clocksource id for arm arch counter [v17,6/7] KVM: arm64: Add support for the KVM PTP service [v17,7/7] ptp: arm/arm64: Enable ptp_kvm for arm/arm64

Context	Check	Description
netdev/tree_selection	success	Not a local patch

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index c136e254b496..7123bedd4248 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6501,3 +6501,12 @@ KVM_GET_DIRTY_LOG and KVM_CLEAR_DIRTY_LOG. After enabling KVM_CAP_DIRTY_LOG_RING with an acceptable dirty ring size, the virtual machine will switch to ring-buffer dirty page tracking and further KVM_GET_DIRTY_LOG or KVM_CLEAR_DIRTY_LOG ioctls will fail. + +8.30 KVM_CAP_PTP_KVM +-------------------- + +:Architectures: arm64 + +This capability indicates that the KVM virtual PTP service is +supported in the host. A VMM can check whether the service is +available to the guest on migration. diff --git a/Documentation/virt/kvm/arm/index.rst b/Documentation/virt/kvm/arm/index.rst index 3e2b2aba90fc..78a9b670aafe 100644 --- a/Documentation/virt/kvm/arm/index.rst +++ b/Documentation/virt/kvm/arm/index.rst @@ -10,3 +10,4 @@ ARM hyp-abi psci pvtime + ptp_kvm diff --git a/Documentation/virt/kvm/arm/ptp_kvm.rst b/Documentation/virt/kvm/arm/ptp_kvm.rst new file mode 100644 index 000000000000..68cffb50d8bf --- /dev/null +++ b/Documentation/virt/kvm/arm/ptp_kvm.rst @@ -0,0 +1,25 @@ +.. SPDX-License-Identifier: GPL-2.0 + +PTP_KVM support for arm/arm64 +============================= + +PTP_KVM is used for high precision time sync between host and guests. +It relies on transferring the wall clock and counter value from the +host to the guest using a KVM-specific hypercall. + +* ARM_SMCCC_HYP_KVM_PTP_FUNC_ID: 0x86000001 + +This hypercall uses the SMC32/HVC32 calling convention: + +ARM_SMCCC_HYP_KVM_PTP_FUNC_ID + ============= ========== ========== + Function ID: (uint32) 0x86000001 + Arguments: (uint32) KVM_PTP_VIRT_COUNTER(0) + KVM_PTP_PHYS_COUNTER(1) + Return Values: (int32) NOT_SUPPORTED(-1) on error, or + (uint32) Upper 32 bits of wall clock time (r0) + (uint32) Lower 32 bits of wall clock time (r1) + (uint32) Upper 32 bits of counter (r2) + (uint32) Lower 32 bits of counter (r3) + Endianness: No Restrictions. + ============= ========== ========== diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 04c44853b103..7ce851fc5643 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -206,6 +206,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) case KVM_CAP_ARM_INJECT_EXT_DABT: case KVM_CAP_SET_GUEST_DEBUG: case KVM_CAP_VCPU_ATTRIBUTES: + case KVM_CAP_PTP_KVM: r = 1; break; case KVM_CAP_ARM_SET_DEVICE_ADDR: diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c index b9d8607083eb..71812879f503 100644 --- a/arch/arm64/kvm/hypercalls.c +++ b/arch/arm64/kvm/hypercalls.c @@ -9,6 +9,55 @@ #include <kvm/arm_hypercalls.h> #include <kvm/arm_psci.h> +static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val) +{ + struct system_time_snapshot systime_snapshot; + u64 cycles = ~0UL; + u32 feature; + + /* + * system time and counter value must captured at the same + * time to keep consistency and precision. + */ + ktime_get_snapshot(&systime_snapshot); + + /* + * This is only valid if the current clocksource is the + * architected counter, as this is the only one the guest + * can see. + */ + if (systime_snapshot.cs_id != CSID_ARM_ARCH_COUNTER) + return; + + /* + * The guest selects one of the two reference counters + * (virtual or physical) with the first argument of the SMCCC + * call. In case the identifier is not supported, error out. + */ + feature = smccc_get_arg1(vcpu); + switch (feature) { + case KVM_PTP_VIRT_COUNTER: + cycles = systime_snapshot.cycles - vcpu_read_sys_reg(vcpu, CNTVOFF_EL2); + break; + case KVM_PTP_PHYS_COUNTER: + cycles = systime_snapshot.cycles; + break; + default: + return; + } + + /* + * This relies on the top bit of val[0] never being set for + * valid values of system time, because that is *really* far + * in the future (about 292 years from 1970, and at that stage + * nobody will give a damn about it). + */ + val[0] = upper_32_bits(systime_snapshot.real); + val[1] = lower_32_bits(systime_snapshot.real); + val[2] = upper_32_bits(cycles); + val[3] = lower_32_bits(cycles); +} + int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) { u32 func_id = smccc_get_function(vcpu); @@ -79,6 +128,10 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) break; case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID: val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES); + val[0] |= BIT(ARM_SMCCC_KVM_FUNC_PTP); + break; + case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID: + kvm_ptp_get_time(vcpu, val); break; default: return kvm_psci_call(vcpu); diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h index 74e90b65b489..96d4973d42d3 100644 --- a/include/linux/arm-smccc.h +++ b/include/linux/arm-smccc.h @@ -103,6 +103,7 @@ /* KVM "vendor specific" services */ #define ARM_SMCCC_KVM_FUNC_FEATURES 0 +#define ARM_SMCCC_KVM_FUNC_PTP 1 #define ARM_SMCCC_KVM_FUNC_FEATURES_2 127 #define ARM_SMCCC_KVM_NUM_FUNCS 128 @@ -114,6 +115,21 @@ #define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1 +/* + * ptp_kvm is a feature used for time sync between vm and host. + * ptp_kvm module in guest kernel will get service from host using + * this hypercall ID. + */ +#define ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID \ + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ + ARM_SMCCC_SMC_32, \ + ARM_SMCCC_OWNER_VENDOR_HYP, \ + ARM_SMCCC_KVM_FUNC_PTP) + +/* ptp_kvm counter type ID */ +#define KVM_PTP_VIRT_COUNTER 0 +#define KVM_PTP_PHYS_COUNTER 1 + /* Paravirtualised time calls (defined by ARM DEN0057A) */ #define ARM_SMCCC_HV_PV_TIME_FEATURES \ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index 374c67875cdb..ef75c3532759 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -1058,6 +1058,7 @@ struct kvm_ppc_resize_hpt { #define KVM_CAP_ENFORCE_PV_FEATURE_CPUID 190 #define KVM_CAP_SYS_HYPERV_CPUID 191 #define KVM_CAP_DIRTY_LOG_RING 192 +#define KVM_CAP_PTP_KVM 193 #ifdef KVM_CAP_IRQ_ROUTING

[v17,6/7] KVM: arm64: Add support for the KVM PTP service

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