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

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Date:   Mon, 7 Nov 2022 18:09:13 +0000
From:   Usama Arif <usama.arif@...edance.com>
To:     Punit Agrawal <punit.agrawal@...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
Subject: Re: [v2 3/6] KVM: arm64: Support pvlock preempted via shared
 structure



On 07/11/2022 18:02, Punit Agrawal wrote:
> 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.
> 
Yes makes sense, will change in next patchset, Thanks.

> [...]
>