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From: yezengruan <yezengruan@huawei.com>
To: Steven Price <steven.price@arm.com>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>,
	"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
	"linux-doc@vger.kernel.org" <linux-doc@vger.kernel.org>,
	"virtualization@lists.linux-foundation.org" 
	<virtualization@lists.linux-foundation.org>,
	"maz@kernel.org" <maz@kernel.org>,
	James Morse <James.Morse@arm.com>,
	"linux@armlinux.org.uk" <linux@armlinux.org.uk>,
	Suzuki Poulose <Suzuki.Poulose@arm.com>,
	"julien.thierry.kdev@gmail.com" <julien.thierry.kdev@gmail.com>,
	"Catalin Marinas" <Catalin.Marinas@arm.com>,
	Mark Rutland <Mark.Rutland@arm.com>,
	"will@kernel.org" <will@kernel.org>,
	"daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>
Subject: Re: [PATCH 1/5] KVM: arm64: Document PV-lock interface
Date: Thu, 19 Dec 2019 19:45:55 +0800
Message-ID: <49120a3c-405d-d2e3-2a88-ba590feccbcc@huawei.com> (raw)
In-Reply-To: <20191217142138.GA38811@arm.com>

Hi Steve,

On 2019/12/17 22:21, Steven Price wrote:
> On Tue, Dec 17, 2019 at 01:55:45PM +0000, yezengruan@huawei.com wrote:
>> From: Zengruan Ye <yezengruan@huawei.com>
>>
>> Introduce a paravirtualization interface for KVM/arm64 to obtain the vcpu
>> is currently running or not.
>>
>> A hypercall interface is provided for the guest to interrogate the
>> hypervisor's support for this interface and the location of the shared
>> memory structures.
>>
>> Signed-off-by: Zengruan Ye <yezengruan@huawei.com>
>> ---
>>  Documentation/virt/kvm/arm/pvlock.rst | 31 +++++++++++++++++++++++++++
>>  1 file changed, 31 insertions(+)
>>  create mode 100644 Documentation/virt/kvm/arm/pvlock.rst
>>
>> diff --git a/Documentation/virt/kvm/arm/pvlock.rst b/Documentation/virt/kvm/arm/pvlock.rst
>> new file mode 100644
>> index 000000000000..eec0c36edf17
>> --- /dev/null
>> +++ b/Documentation/virt/kvm/arm/pvlock.rst
>> @@ -0,0 +1,31 @@
>> +.. SPDX-License-Identifier: GPL-2.0
>> +
>> +Paravirtualized lock support for arm64
>> +======================================
>> +
>> +KVM/arm64 provids some hypervisor service calls to support a paravirtualized
>> +guest obtaining the vcpu is currently running or not.
>> +
>> +Two new SMCCC compatible hypercalls are defined:
>> +
>> +* PV_LOCK_FEATURES:   0xC5000040
>> +* PV_LOCK_PREEMPTED:  0xC5000041
> 
> These values are in the "Standard Hypervisor Service Calls" section of
> SMCCC - so is there a document that describes this features such that
> other OSes or hypervisors can implement it? I'm also not entirely sure
> of the process of ensuring that the IDs picked are non-conflicting.
> 
> Otherwise if this is a KVM specific interface this should probably
> belong within the "Vendor Specific Hypervisor Service Calls" section
> along with some probing that the hypervisor is actually KVM. Although I
> don't see anything KVM specific.

Thanks for pointing it out to me! Actually, I also don't see any documents
or KVM specific that describes this features. The values in the "Vendor
Specific Hypervisor Service Calls" section may be more appropriate, such as
the following

* PV_LOCK_FEATURES:   0xC6000020
* PV_LOCK_PREEMPTED:  0xC6000021

Please let me know if you have any suggestions.

> 
>> +
>> +The existence of the PV_LOCK hypercall should be probed using the SMCCC 1.1
>> +ARCH_FEATURES mechanism before calling it.
>> +
>> +PV_LOCK_FEATURES
>> +    ============= ========    ==========
>> +    Function ID:  (uint32)    0xC5000040
>> +    PV_call_id:   (uint32)    The function to query for support.
>> +    Return value: (int64)     NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
>> +                              PV-lock feature is supported by the hypervisor.
>> +    ============= ========    ==========
>> +
>> +PV_LOCK_PREEMPTED
>> +    ============= ========    ==========
>> +    Function ID:  (uint32)    0xC5000041
>> +    Return value: (int64)     NOT_SUPPORTED (-1) or SUCCESS (0) if the IPA of
>> +                              this vcpu's pv data structure is configured by
>> +                              the hypervisor.
>> +    ============= ========    ==========
> 
>>From the code it looks like there's another argument for this SMC - the
> physical address (or IPA) of a struct pvlock_vcpu_state. This structure
> also needs to be described as it is part of the ABI.

Will update.

> 
> Steve
> 
> .
> 

Thanks,

Zengruan



  reply index

Thread overview: 17+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-17 13:55 [PATCH 0/5] KVM: arm64: vcpu preempted check support yezengruan
2019-12-17 13:55 ` [PATCH 1/5] KVM: arm64: Document PV-lock interface yezengruan
2019-12-17 14:21   ` Steven Price
2019-12-19 11:45     ` yezengruan [this message]
2019-12-20 11:43       ` Steven Price
2019-12-20 14:32   ` Markus Elfring
2019-12-23  2:06     ` yezengruan
2019-12-17 13:55 ` [PATCH 2/5] KVM: arm64: Implement PV_LOCK_FEATURES call yezengruan
2019-12-17 14:28   ` Steven Price
2019-12-19 11:59     ` yezengruan
2019-12-17 13:55 ` [PATCH 3/5] KVM: arm64: Support pvlock preempted via shared structure yezengruan
2019-12-17 14:33   ` Steven Price
2019-12-26  8:33     ` yezengruan
2019-12-17 13:55 ` [PATCH 4/5] KVM: arm64: Add interface to support vcpu preempted check yezengruan
2019-12-17 13:55 ` [PATCH 5/5] KVM: arm64: Support the vcpu preemption check yezengruan
2019-12-17 14:40   ` Steven Price
2019-12-26  8:34     ` yezengruan

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