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From: Steven Price <steven.price@arm.com>
To: "yezengruan@huawei.com" <yezengruan@huawei.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: Tue, 17 Dec 2019 14:21:39 +0000
Message-ID: <20191217142138.GA38811@arm.com> (raw)
In-Reply-To: <20191217135549.3240-2-yezengruan@huawei.com>

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.

> +
> +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.

Steve

  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 [this message]
2019-12-19 11:45     ` yezengruan
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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