linux-kernel - Re: [v2 3/6] KVM: arm64: Support pvlock preempted via shared structure

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Date:   Mon, 07 Nov 2022 18:02:01 +0000
From:   Punit Agrawal <punit.agrawal@...edance.com>
To:     Usama Arif <usama.arif@...edance.com>
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        linux-doc@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, linux@...linux.org.uk,
        yezengruan@...wei.com, catalin.marinas@....com, will@...nel.org,
        maz@...nel.org, steven.price@....com, mark.rutland@....com,
        bagasdotme@...il.com, fam.zheng@...edance.com,
        liangma@...ngbit.com, punit.agrawal@...edance.com
Subject: Re: [v2 3/6] KVM: arm64: Support pvlock preempted via shared structure

Usama Arif <usama.arif@...edance.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@...wei.com>
> Signed-off-by: Usama Arif <usama.arif@...edance.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.

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