linux-kernel - Re: [PATCH RFCv2 4/9] kvm/arm64: Detach ESR operator from vCPU struct

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Message-ID: <4cda1e43-8f96-4e48-2642-39a5545905c0@redhat.com>
Date:   Wed, 27 May 2020 12:55:04 +1000
From:   Gavin Shan <gshan@...hat.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, maz@...nel.org, will@...nel.org,
        catalin.marinas@....com, james.morse@....com,
        suzuki.poulose@....com, drjones@...hat.com, eric.auger@...hat.com,
        aarcange@...hat.com, shan.gavin@...il.com
Subject: Re: [PATCH RFCv2 4/9] kvm/arm64: Detach ESR operator from vCPU struct

Hi Mark,

On 5/26/20 8:51 PM, Mark Rutland wrote:
> On Fri, May 08, 2020 at 01:29:14PM +1000, Gavin Shan wrote:
>> There are a set of inline functions defined in kvm_emulate.h. Those
>> functions reads ESR from vCPU fault information struct and then operate
>> on it. So it's tied with vCPU fault information and vCPU struct. It
>> limits their usage scope.
>>
>> This detaches these functions from the vCPU struct. With this, the
>> caller has flexibility on where the ESR is read. It shouldn't cause
>> any functional changes.
>>
>> Signed-off-by: Gavin Shan <gshan@...hat.com>
>> ---
>>   arch/arm64/include/asm/kvm_emulate.h     | 83 +++++++++++-------------
>>   arch/arm64/kvm/handle_exit.c             | 20 ++++--
>>   arch/arm64/kvm/hyp/switch.c              | 24 ++++---
>>   arch/arm64/kvm/hyp/vgic-v2-cpuif-proxy.c |  7 +-
>>   arch/arm64/kvm/inject_fault.c            |  4 +-
>>   arch/arm64/kvm/sys_regs.c                | 12 ++--
>>   virt/kvm/arm/arm.c                       |  4 +-
>>   virt/kvm/arm/hyp/aarch32.c               |  2 +-
>>   virt/kvm/arm/hyp/vgic-v3-sr.c            |  5 +-
>>   virt/kvm/arm/mmio.c                      | 27 ++++----
>>   virt/kvm/arm/mmu.c                       | 22 ++++---
>>   11 files changed, 112 insertions(+), 98 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index bd1a69e7c104..2873bf6dc85e 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -270,10 +270,8 @@ static __always_inline u32 kvm_vcpu_get_esr(const struct kvm_vcpu *vcpu)
>>   	return vcpu->arch.fault.esr_el2;
>>   }
>>   
>> -static __always_inline int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
>> +static __always_inline int kvm_vcpu_get_condition(u32 esr)
> 
> Given the `vcpu` argument has been removed, it's odd to keep `vcpu` in the
> name, rather than `esr`.
> 
> e.g. this would make more sense as something like esr_get_condition().
> 
> ... and if we did something like that, we could move most of the
> extraction functions into <asm/esr.h>, and share them with non-KVM code.
> 
> Otherwise, do you need to extract all of these for your use-case, or do
> you only need a few of the helpers? If you only need a few, it might be
> better to only factor those out for now, and keep the existing API in
> place with wrappers, e.g. have:
> 
> | esr_get_condition(u32 esr) {
> | 	...
> | }
> |
> | kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
> | {
> | 	return esr_get_condition(kvm_vcpu_get_esr(vcpu));
> | }
> 

Sure, I'll follow approach#1, to move these helper functions to asm/esr.h
and with "vcpu" dropped in their names. I don't think it makes sense to
maintain two sets of helper functions for the simple logic. So the helper
function will be called where they should be, as below:

    esr_get_condition(u32 esr) { ... }
    
    bool __hyp_text kvm_condition_valid32(const struct kvm_vcpu *vcpu)
    {
         int cond = esr_get_condition(kvm_vcpu_get_esr(vcpu));
         :
    }

Thanks,
Gavin