Messages in this thread | | | Date | Mon, 23 Nov 2020 10:44:12 +0000 | From | Marc Zyngier <> | Subject | Re: [PATCH v15 6/9] arm64/kvm: Add hypercall service for kvm ptp. |
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On 2020-11-11 06:22, Jianyong Wu wrote: > ptp_kvm will get this service through SMCC call. > The service offers wall time and cycle count of host to guest. > The caller must specify whether they want the host cycle count > or the difference between host cycle count and cntvoff. > > Signed-off-by: Jianyong Wu <jianyong.wu@arm.com> > --- > arch/arm64/kvm/hypercalls.c | 61 +++++++++++++++++++++++++++++++++++++ > include/linux/arm-smccc.h | 17 +++++++++++ > 2 files changed, 78 insertions(+) > > diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c > index b9d8607083eb..f7d189563f3d 100644 > --- a/arch/arm64/kvm/hypercalls.c > +++ b/arch/arm64/kvm/hypercalls.c > @@ -9,6 +9,51 @@ > #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 in the same > + * time to keep consistency and precision. > + */ > + ktime_get_snapshot(&systime_snapshot); > + > + // binding ptp_kvm clocksource to arm_arch_counter > + if (systime_snapshot.cs_id != CSID_ARM_ARCH_COUNTER) > + return; > + > + val[0] = upper_32_bits(systime_snapshot.real); > + val[1] = lower_32_bits(systime_snapshot.real);
What is the endianness of these values? I can't see it defined anywhere, and this is likely not to work if guest and hypervisor don't align.
> + > + /* > + * which of virtual counter or physical counter being > + * asked for is decided by the r1 value of SMCCC > + * call. If no invalid r1 value offered, default cycle > + * value(-1) will be returned. > + * Note: keep in mind that feature is u32 and smccc_get_arg1 > + * will return u64, so need auto cast here. > + */ > + feature = smccc_get_arg1(vcpu); > + switch (feature) { > + case ARM_PTP_VIRT_COUNTER: > + cycles = systime_snapshot.cycles - vcpu_read_sys_reg(vcpu, > CNTVOFF_EL2); > + break; > + case ARM_PTP_PHY_COUNTER: > + cycles = systime_snapshot.cycles; > + break; > + case ARM_PTP_NONE_COUNTER:
What is this "NONE" counter?
> + break; > + default: > + val[0] = SMCCC_RET_NOT_SUPPORTED; > + break; > + } > + val[2] = upper_32_bits(cycles); > + val[3] = lower_32_bits(cycles);
Same problem as above.
> +} > + > int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) > { > u32 func_id = smccc_get_function(vcpu); > @@ -79,6 +124,22 @@ 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_KVM_PTP); > + break; > + /* > + * This serves virtual kvm_ptp. > + * Four values will be passed back. > + * reg0 stores high 32-bits of host ktime; > + * reg1 stores low 32-bits of host ktime; > + * For ARM_PTP_VIRT_COUNTER: > + * reg2 stores high 32-bits of difference of host cycles and cntvoff; > + * reg3 stores low 32-bits of difference of host cycles and cntvoff. > + * For ARM_PTP_PHY_COUNTER: > + * reg2 stores the high 32-bits of host cycles; > + * reg3 stores the low 32-bits of host cycles. > + */ > + 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 d75408141137..a03c5dd409d3 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_KVM_PTP 1
I think having KVM once in the name is enough.
> #define ARM_SMCCC_KVM_FUNC_FEATURES_2 127 > #define ARM_SMCCC_KVM_NUM_FUNCS 128 > > @@ -114,6 +115,22 @@ > > #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_KVM_PTP) > + > +/* ptp_kvm counter type ID */ > +#define ARM_PTP_VIRT_COUNTER 0 > +#define ARM_PTP_PHY_COUNTER 1 > +#define ARM_PTP_NONE_COUNTER 2
The architecture definitely doesn't have this last counter.
> + > /* Paravirtualised time calls (defined by ARM DEN0057A) */ > #define ARM_SMCCC_HV_PV_TIME_FEATURES \ > ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
Thanks,
M. -- Jazz is not dead. It just smells funny...
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