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From: Marc Zyngier <maz@kernel.org>
To: Steven Price <steven.price@arm.com>
Cc: kvm@vger.kernel.org, Catalin Marinas <catalin.marinas@arm.com>,
	linux-doc@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
	linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Paolo Bonzini <pbonzini@redhat.com>,
	Will Deacon <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu
Subject: Re: [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest
Date: Thu, 8 Aug 2019 16:49:45 +0100
Message-ID: <7108a70b-dafd-507b-8509-f4a092ef24af@kernel.org> (raw)
In-Reply-To: <dc8a1e56-7b52-cc8f-265d-27eb5f458613@arm.com>

On 08/08/2019 16:29, Steven Price wrote:
> On 04/08/2019 10:53, Marc Zyngier wrote:
>> On Fri,  2 Aug 2019 15:50:17 +0100
>> Steven Price <steven.price@arm.com> wrote:
>>
>>> Enable paravirtualization features when running under a hypervisor
>>> supporting the PV_TIME_ST hypercall.
>>>
>>> For each (v)CPU, we ask the hypervisor for the location of a shared
>>> page which the hypervisor will use to report stolen time to us. We set
>>> pv_time_ops to the stolen time function which simply reads the stolen
>>> value from the shared page for a VCPU. We guarantee single-copy
>>> atomicity using READ_ONCE which means we can also read the stolen
>>> time for another VCPU than the currently running one while it is
>>> potentially being updated by the hypervisor.
>>>
>>> Signed-off-by: Steven Price <steven.price@arm.com>
>>> ---
>>>  arch/arm64/kernel/Makefile |   1 +
>>>  arch/arm64/kernel/kvm.c    | 155 +++++++++++++++++++++++++++++++++++++

[...]

>>> +static int __init kvm_guest_init(void)
>>> +{
>>> +	int ret = 0;
>>> +
>>> +	if (!has_kvm_steal_clock())
>>> +		return 0;
>>> +
>>> +	ret = kvm_arm_init_stolen_time();
>>> +	if (ret)
>>> +		return ret;
>>> +
>>> +	pv_ops.time.steal_clock = kvm_steal_clock;
>>> +
>>> +	static_key_slow_inc(&paravirt_steal_enabled);
>>> +	if (steal_acc)
>>> +		static_key_slow_inc(&paravirt_steal_rq_enabled);
>>> +
>>> +	pr_info("using stolen time PV\n");
>>> +
>>> +	return 0;
>>> +}
>>> +early_initcall(kvm_guest_init);
>>
>> Is there any reason why we wouldn't directly call into this rather than
>> using an initcall?
> 
> I'm not sure where the direct call would go - any pointers?

I'd be temped to say arch/arm64/kernel/time.c:time_init(), provided that
there is no issue with the CPU hotplug lock (I remember hitting that a
while ago).

	M.
-- 
Jazz is not dead, it just smells funny...
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Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-02 14:50 [PATCH 0/9] arm64: Stolen time support Steven Price
2019-08-02 14:50 ` [PATCH 1/9] KVM: arm64: Document PV-time interface Steven Price
2019-08-03 11:13   ` Marc Zyngier
2019-08-05 13:06     ` Steven Price
2019-08-05  3:23   ` Zenghui Yu
2019-08-05 13:06     ` Steven Price
2019-08-05 16:40   ` Christophe de Dinechin
2019-08-07 13:21     ` Steven Price
2019-08-07 14:28       ` Christophe de Dinechin
2019-08-07 15:26         ` Steven Price
2019-08-02 14:50 ` [PATCH 2/9] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-08-02 14:50 ` [PATCH 3/9] KVM: arm64: Implement PV_FEATURES call Steven Price
2019-08-03 11:21   ` Marc Zyngier
2019-08-05 13:14     ` Steven Price
2019-08-02 14:50 ` [PATCH 4/9] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-08-03 11:55   ` Marc Zyngier
2019-08-05 14:09     ` Steven Price
2019-08-03 17:58   ` Marc Zyngier
2019-08-03 18:13     ` Marc Zyngier
2019-08-05 14:18       ` Steven Price
2019-08-02 14:50 ` [PATCH 5/9] KVM: Allow kvm_device_ops to be const Steven Price
2019-08-02 14:50 ` [PATCH 6/9] KVM: arm64: Provide a PV_TIME device to user space Steven Price
2019-08-03 12:51   ` Marc Zyngier
2019-08-03 17:34     ` Marc Zyngier
2019-08-07 13:39       ` Steven Price
2019-08-07 13:51         ` Marc Zyngier
2019-08-05 16:10     ` Steven Price
2019-08-05 16:28       ` Marc Zyngier
2019-08-02 14:50 ` [PATCH 7/9] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-08-05 10:03   ` Will Deacon
2019-08-02 14:50 ` [PATCH 8/9] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-08-02 14:50 ` [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest Steven Price
2019-08-04  9:53   ` Marc Zyngier
2019-08-08 15:29     ` Steven Price
2019-08-08 15:49       ` Marc Zyngier [this message]
2019-08-09 13:51   ` Zenghui Yu
2019-08-12 10:39     ` Steven Price
2019-08-13  6:06       ` Zenghui Yu
2019-08-03 18:05 ` [PATCH 0/9] arm64: Stolen time support Marc Zyngier
2019-08-05 13:06   ` Steven Price
2019-08-05 13:26     ` Marc Zyngier
2019-08-14 13:02     ` Alexander Graf
2019-08-14 14:19       ` Marc Zyngier
2019-08-14 14:52         ` [UNVERIFIED SENDER] " Alexander Graf
2019-08-16 10:23           ` Steven Price

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