Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
From:   Punit Agrawal <punit.agrawal@bytedance.com>
To:     Usama Arif <usama.arif@bytedance.com>
Cc:     linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        kvmarm@lists.cs.columbia.edu, kvm@vger.kernel.org,
        linux-doc@vger.kernel.org,
        virtualization@lists.linux-foundation.org, linux@armlinux.org.uk,
        yezengruan@huawei.com, catalin.marinas@arm.com, will@kernel.org,
        maz@kernel.org, steven.price@arm.com, mark.rutland@arm.com,
        bagasdotme@gmail.com, fam.zheng@bytedance.com,
        liangma@liangbit.com, punit.agrawal@bytedance.com
Subject: Re: [v2 3/6] KVM: arm64: Support pvlock preempted via shared structure
References: <20221104062105.4119003-1-usama.arif@bytedance.com>
        <20221104062105.4119003-4-usama.arif@bytedance.com>
Date:   Mon, 07 Nov 2022 18:02:01 +0000
Message-ID: <8735au3ap2.fsf@stealth>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Usama Arif <usama.arif@bytedance.com> writes:

> Implement the service call for configuring a shared structure between a
> VCPU and the hypervisor in which the hypervisor can tell whether the
> VCPU is running or not.
>
> The preempted field is zero if the VCPU is not preempted.
> Any other value means the VCPU has been preempted.
>
> Signed-off-by: Zengruan Ye <yezengruan@huawei.com>
> Signed-off-by: Usama Arif <usama.arif@bytedance.com>
> ---
>  Documentation/virt/kvm/arm/hypercalls.rst |  3 ++
>  arch/arm64/include/asm/kvm_host.h         | 18 ++++++++++
>  arch/arm64/include/uapi/asm/kvm.h         |  1 +
>  arch/arm64/kvm/Makefile                   |  2 +-
>  arch/arm64/kvm/arm.c                      |  8 +++++
>  arch/arm64/kvm/hypercalls.c               |  8 +++++
>  arch/arm64/kvm/pvlock.c                   | 43 +++++++++++++++++++++++
>  tools/arch/arm64/include/uapi/asm/kvm.h   |  1 +
>  8 files changed, 83 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/kvm/pvlock.c
>
> diff --git a/Documentation/virt/kvm/arm/hypercalls.rst b/Documentation/virt/kvm/arm/hypercalls.rst
> index 3e23084644ba..872a16226ace 100644
> --- a/Documentation/virt/kvm/arm/hypercalls.rst
> +++ b/Documentation/virt/kvm/arm/hypercalls.rst
> @@ -127,6 +127,9 @@ The pseudo-firmware bitmap register are as follows:
>      Bit-1: KVM_REG_ARM_VENDOR_HYP_BIT_PTP:
>        The bit represents the Precision Time Protocol KVM service.
>  
> +    Bit-2: KVM_REG_ARM_VENDOR_HYP_BIT_PV_LOCK:
> +      The bit represents the Paravirtualized lock service.
> +
>  Errors:
>  
>      =======  =============================================================
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index 45e2136322ba..18303b30b7e9 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -417,6 +417,11 @@ struct kvm_vcpu_arch {
>  		u64 last_steal;
>  		gpa_t base;
>  	} steal;
> +
> +	/* Guest PV lock state */
> +	struct {
> +		gpa_t base;
> +	} pv;

Using "pv" for the structure isn't quite describing the usage well. It'd
be better to call it "pv_lock" or "pvlock" at the least.

[...]