From: Marc Zyngier <maz@kernel.org>
To: Jianyong Wu <Jianyong.Wu@arm.com>
Cc: Mark Rutland <Mark.Rutland@arm.com>,
Justin He <Justin.He@arm.com>,
kvm@vger.kernel.org, Suzuki Poulose <Suzuki.Poulose@arm.com>,
netdev@vger.kernel.org, richardcochran@gmail.com,
Steve Capper <Steve.Capper@arm.com>,
linux-kernel@vger.kernel.org, sean.j.christopherson@intel.com,
Steven Price <Steven.Price@arm.com>, Kaly Xin <Kaly.Xin@arm.com>,
john.stultz@linaro.org, yangbo.lu@nxp.com, pbonzini@redhat.com,
tglx@linutronix.de, nd <nd@arm.com>,
will@kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH v9 6/8] psci: Add hvc call service for ptp_kvm.
Date: Mon, 13 Jan 2020 11:16:26 +0000 [thread overview]
Message-ID: <22ba1283a7b82f018c1fdf85414e5bfe@kernel.org> (raw)
In-Reply-To: <HE1PR0801MB167693BFB769ACEEA8A6B007F4350@HE1PR0801MB1676.eurprd08.prod.outlook.com>
Hi Jianyong,
On 2020-01-13 10:30, Jianyong Wu wrote:
> Hi Marc,
>
>> -----Original Message-----
>> From: Marc Zyngier <maz@kernel.org>
>> Sent: Friday, January 10, 2020 6:56 PM
>> NV breaks that assumtion, because the guest hypervisor is using the
>> physical
>> counter. Also, let's not forget that the hypercall isn't Linux
>> specific.
>> I can write my own non-Linux guest and still use this hypercall.
>> Nothing in
>> there says that I can't use the physical counter if I want to.
>>
>> So somehow, you need to convey the the hypervisor the notion of
>> *which*
>> counter the guest uses.
>>
>> Does it make sense? Or am I missing something?
>>
> I know what you say. Let me try to solve this problem.
> Step 0, summary out all the conditions we should process, which will
> sever as branch condition.(now only normal virt and nested virt, I
> think)
No. You shouldn't think of the various use cases, but of which time
references a guest can use. You don't need nested virt to use the
physical
counter, for example.
> Step 1, figure out the set of reference counter value used by guest
> in all condition.
That should be for the guest to tell you when it calls into the PV
service.
> Step 2, determine which reference counter value will be used by guest
> in a certain condition in hypercall.
> In step 1, can we give the set only 2 elements that one is physical
> counter the other is virtual counter?
I don't think returning the two values is useful. Just return what the
guest asks for.
> For step 2, I have no idea for that now. can you give me some hint
> about it?
Just expand your SMC call to take a parameter indicating the reference
counter, and return the sampled (or computed) value corresponding to
that counter.
M.
--
Jazz is not dead. It just smells funny...
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next prev parent reply other threads:[~2020-01-13 11:16 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-10 3:40 [RFC PATCH v9 0/8] Enable ptp_kvm for arm64 Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 1/8] arm/arm64: smccc/psci: add arm_smccc_1_1_get_conduit() Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 2/8] psci: let arm_smccc_1_1_invoke available by modules Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 3/8] ptp: Reorganize ptp_kvm modules to make it arch-independent Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 4/8] time: Add mechanism to recognize clocksource in time_get_snapshot Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 5/8] clocksource: Add clocksource id for arm arch counter Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 6/8] psci: Add hvc call service for ptp_kvm Jianyong Wu
2020-01-07 9:16 ` Marc Zyngier
2020-01-09 5:45 ` Jianyong Wu
2020-01-09 9:16 ` Marc Zyngier
2020-01-10 9:51 ` Jianyong Wu
2020-01-10 10:56 ` Marc Zyngier
2020-01-13 10:30 ` Jianyong Wu
2020-01-13 11:16 ` Marc Zyngier [this message]
2020-01-14 10:34 ` Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 7/8] ptp: arm64: Enable ptp_kvm for arm64 Jianyong Wu
2020-01-07 9:29 ` Marc Zyngier
2020-01-09 5:59 ` Jianyong Wu
2020-01-09 9:24 ` Marc Zyngier
2020-01-09 9:46 ` Marc Zyngier
2020-01-10 10:15 ` Jianyong Wu
2020-01-10 10:15 ` Jianyong Wu
2020-01-10 10:35 ` Marc Zyngier
2020-01-13 10:37 ` Jianyong Wu
2020-01-13 11:21 ` Marc Zyngier
2020-01-14 10:22 ` Jianyong Wu
2019-12-10 3:40 ` [RFC PATCH v9 8/8] kvm: arm64: Add capability check extension for ptp_kvm Jianyong Wu
2020-01-06 9:38 ` [RFC PATCH v9 0/8] Enable ptp_kvm for arm64 Jianyong Wu
2020-01-07 8:15 ` Paolo Bonzini
2020-01-07 9:33 ` Marc Zyngier
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