Re: [PATCH v9 21/21] KVM: ARM64: Add a new vcpu device control group for PMUv3

From: Peter Maydell <peter.maydell@linaro.org>
To: Shannon Zhao <zhaoshenglong@huawei.com>
Cc: kvm-devel <kvm@vger.kernel.org>,
	Marc Zyngier <marc.zyngier@arm.com>,
	Shannon Zhao <shannon.zhao@linaro.org>,
	Will Deacon <will.deacon@arm.com>,
	arm-mail-list <linux-arm-kernel@lists.infradead.org>,
	"kvmarm@lists.cs.columbia.edu" <kvmarm@lists.cs.columbia.edu>
Subject: Re: [PATCH v9 21/21] KVM: ARM64: Add a new vcpu device control group for PMUv3
Date: Mon, 25 Jan 2016 16:53:02 +0000	[thread overview]
Message-ID: <CAFEAcA-rVDLajQ7s5KcwkVsACtRtEqN+wkpR6RWMkvBBPJY8fA@mail.gmail.com> (raw)
In-Reply-To: <1452839275-19368-22-git-send-email-zhaoshenglong@huawei.com>

On 15 January 2016 at 06:27, Shannon Zhao <zhaoshenglong@huawei.com> wrote:
> From: Shannon Zhao <shannon.zhao@linaro.org>
>
> To configure the virtual PMUv3 overflow interrupt number, we use the
> vcpu kvm_device ioctl, encapsulating the KVM_ARM_VCPU_PMU_V3_IRQ
> attribute within the KVM_ARM_VCPU_PMU_V3_CTRL group.
>
> After configuring the PMUv3, call the vcpu iotcl with attribute
> KVM_ARM_VCPU_PMU_V3_INIT to initialize the PMUv3.
>
> Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
> ---
> CC: Peter Maydell <peter.maydell@linaro.org>
> ---
>  Documentation/virtual/kvm/devices/vcpu.txt |  24 ++++++
>  arch/arm/include/asm/kvm_host.h            |  15 ++++
>  arch/arm/kvm/arm.c                         |   3 +
>  arch/arm64/include/asm/kvm_host.h          |   6 ++
>  arch/arm64/include/uapi/asm/kvm.h          |   5 ++
>  arch/arm64/kvm/guest.c                     |  51 ++++++++++++
>  include/kvm/arm_pmu.h                      |  23 ++++++
>  virt/kvm/arm/pmu.c                         | 128 +++++++++++++++++++++++++++++
>  8 files changed, 255 insertions(+)
>
> diff --git a/Documentation/virtual/kvm/devices/vcpu.txt b/Documentation/virtual/kvm/devices/vcpu.txt
> index 3cc59c5..60cbac8 100644
> --- a/Documentation/virtual/kvm/devices/vcpu.txt
> +++ b/Documentation/virtual/kvm/devices/vcpu.txt
> @@ -6,3 +6,27 @@ KVM_GET_DEVICE_ATTR, and KVM_HAS_DEVICE_ATTR. The interface uses the same struct
>  kvm_device_attr as other devices, but targets VCPU-wide settings and controls.
>
>  The groups and attributes per virtual cpu, if any, are architecture specific.
> +
> +1. GROUP: KVM_ARM_VCPU_PMU_V3_CTRL
> +Architectures: ARM64
> +
> +1.1. ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_IRQ
> +Parameters: in kvm_device_attr.addr the address for PMU overflow interrupt
> +Returns: -EBUSY: The PMU overflow interrupt is already set
> +         -ENODEV: Not set the corresponding vcpu feature bit or getting the PMU
> +                  overflow interrupt number while it's not set
> +         -EINVAL: Invalid PMU overflow interrupt number supplied
> +
> +A value describing the PMUv3 (Performance Monitor Unit v3) overflow interrupt
> +number for this vcpu. This interrupt could be a PPI or SPI, but the interrupt
> +type must be same for each vcpu. As a PPI, the interrupt number is same for all
> +vcpus, while as a SPI it must be different for each vcpu.
> +
> +1.2 ATTRIBUTE: KVM_ARM_VCPU_PMU_V3_INIT
> +Parameters: no additional parameter in kvm_device_attr.addr
> +Returns: -ENODEV: No PMUv3 supported
> +         -ENXIO: PMUv3 not properly configured as required prior to calling this
> +                 attribute
> +         -EBUSY: PMUv3 already initialized
> +
> +Request the initialization of the PMUv3.

The other thing we could do here (now the PMU is part of the vCPU 'device'
rather than its own thing) is to have a single INIT ioctl that says
"we're done doing all the SET_DEVICE_ATTR calls to configure the vCPU".
But I'm fine with this way too.

You can have my
Acked-by: Peter Maydell <peter.maydell@linaro.org>

for the userspace API parts of patches 19, 20 and 21 (with the minor typo
fixes etc Andrew has posted).

thanks
-- PMM