Hi Marc,
-----Original Message-----Ok, I will add them next version.
From: Marc Zyngier <maz@xxxxxxxxxx>
Sent: Tuesday, January 7, 2020 5:16 PM
To: Jianyong Wu <Jianyong.Wu@xxxxxxx>
Cc: netdev@xxxxxxxxxxxxxxx; yangbo.lu@xxxxxxx; john.stultz@xxxxxxxxxx;
tglx@xxxxxxxxxxxxx; pbonzini@xxxxxxxxxx; sean.j.christopherson@xxxxxxxxx;
richardcochran@xxxxxxxxx; Mark Rutland <Mark.Rutland@xxxxxxx>;
will@xxxxxxxxxx; Suzuki Poulose <Suzuki.Poulose@xxxxxxx>; Steven Price
<Steven.Price@xxxxxxx>; linux-kernel@xxxxxxxxxxxxxxx; linux-arm-
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kvm@xxxxxxxxxxxxxxx; Steve Capper <Steve.Capper@xxxxxxx>; Kaly Xin
<Kaly.Xin@xxxxxxx>; Justin He <Justin.He@xxxxxxx>; nd <nd@xxxxxxx>
Subject: Re: [RFC PATCH v9 6/8] psci: Add hvc call service for ptp_kvm.
On 2019-12-10 03:40, Jianyong Wu wrote:
> ptp_kvm modules will call hvc to get this service.
> The service offers real time and counter cycle of host for guest.
>
> Signed-off-by: Jianyong Wu <jianyong.wu@xxxxxxx>
> ---
> include/linux/arm-smccc.h | 12 ++++++++++++
> virt/kvm/arm/psci.c | 22 ++++++++++++++++++++++
> 2 files changed, 34 insertions(+)
>
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 6f82c87308ed..aafb6bac167d 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -94,6 +94,7 @@
>
> /* KVM "vendor specific" services */
> #define ARM_SMCCC_KVM_FUNC_FEATURES 0
> +#define ARM_SMCCC_KVM_PTP 1
> #define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
> #define ARM_SMCCC_KVM_NUM_FUNCS 128
>
> @@ -103,6 +104,17 @@
> ARM_SMCCC_OWNER_VENDOR_HYP,
\
> ARM_SMCCC_KVM_FUNC_FEATURES)
>
> +/*
> + * This ID used for virtual ptp kvm clock and it will pass second
> value
> + * and nanosecond value of host real time and system counter by vcpu
> + * register to guest.
> + */
> +#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_PTP)
> +
All of this depends on patches that have never need posted to any ML, and
just linger in Will's tree. You need to pick them up and post them as part of
this series so that they can at least be reviewed.
> #ifndef __ASSEMBLY__Sorry, I'm not sure what do you mean "three", the registers here is 4
>
> #include <linux/linkage.h>
> diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c index
> 0debf49bf259..682d892d6717 100644
> --- a/virt/kvm/arm/psci.c
> +++ b/virt/kvm/arm/psci.c
> @@ -9,6 +9,7 @@
> #include <linux/kvm_host.h>
> #include <linux/uaccess.h>
> #include <linux/wait.h>
> +#include <linux/clocksource_ids.h>
>
> #include <asm/cputype.h>
> #include <asm/kvm_emulate.h>
> @@ -389,6 +390,8 @@ static int kvm_psci_call(struct kvm_vcpu *vcpu)
>
> int kvm_hvc_call_handler(struct kvm_vcpu *vcpu) {
> + struct system_time_snapshot systime_snapshot;
> + u64 cycles;
> u32 func_id = smccc_get_function(vcpu);
> u32 val[4] = {};
> u32 option;
> @@ -431,6 +434,25 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
> case ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID:
> val[0] = BIT(ARM_SMCCC_KVM_FUNC_FEATURES);
> break;
> + /*
> + * This will used for virtual ptp kvm clock. three
> + * values will be passed back.
> + * reg0 stores high 32-bit host ktime;
> + * reg1 stores low 32-bit host ktime;
> + * reg2 stores high 32-bit difference of host cycles and cntvoff;
> + * reg3 stores low 32-bit difference of host cycles and cntvoff.
That's either two or four values, and not three as you claim above.
from reg0 to reg3.
Also, I fail to understand the meaning of the host cycle vs cntvoff comparison.To keep consistency and precision, clock time and counter cycle must
This is something that guest can perform on its own (it has access to both
physical and virtual timers, and can compute cntvoff without intervention of
the hypervisor).
captured at the same time. It will perform at ktime_get_snapshot.
Finally, how does it work with nested virt, where cntvoff is for the the vEL2For now, I have not considered ptp_kvm in nested virtualization. Also
guest?
I'm not sure about if nested virtualization is
ready on arm64 , as I need test ptp_kvm on it. If so, I can consider it.
> + */Sorry, what I want to do here is that return to guest with the error info.
> + case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
> + ktime_get_snapshot(&systime_snapshot);
> + if (systime_snapshot.cs_id != CSID_ARM_ARCH_COUNTER)
> + return kvm_psci_call(vcpu);
What does this mean? Calling PSCI because you've failed to identify the clock
source? What result do you expect from this? Hint: this isn't a PSCI call.
Maybe I should set val[0] to -1 and break to let the guest know that
error comes, as
the guest will check if val[0] is positive to determine the next step.