Re: [PATCH 10/26] KVM: arm64: Refactor vcpu_{read,write}_sys_reg

Marc Zyngier
2020-05-27T10:04:14Z

On 2020-05-26 17:28, James Morse wrote:
> Hi Marc,
>
> On 22/04/2020 13:00, Marc Zyngier wrote:
>> Extract the direct HW accessors for later reuse.
>
>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>> index 51db934702b64..46f218982df8c 100644
>> --- a/arch/arm64/kvm/sys_regs.c
>> +++ b/arch/arm64/kvm/sys_regs.c
>
>> +u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
>> +{
>> + u64 val = 0x8badf00d8badf00d;
>> +
>> + if (!vcpu->arch.sysregs_loaded_on_cpu) {
>> + goto memory_read;
>> }
>>
>> -immediate_write:
>> + if (__vcpu_read_sys_reg_from_cpu(reg, &val))
>> + return val;
>> +
>> +memory_read:
>> + return __vcpu_sys_reg(vcpu, reg);
>> +}
>
>
> The goto here is a bit odd, is it just an artefact of how we got here?

That's because a lot of this changes when NV gets added to the mix,
see [1].

> Is this easier on the eye?:
> | u64 vcpu_read_sys_reg(const struct kvm_vcpu *vcpu, int reg)
> | {
> | u64 val = 0x8badf00d8badf00d;
> |
> | if (vcpu->arch.sysregs_loaded_on_cpu &&
> | __vcpu_read_sys_reg_from_cpu(reg, &val))
> | return val;
> |
> | return __vcpu_sys_reg(vcpu, reg);
> | }

Definitely. I don't mind reworking the NV branch so that the label
gets introduced there.

>> +void vcpu_write_sys_reg(struct kvm_vcpu *vcpu, u64 val, int reg)
>> +{
>> + if (!vcpu->arch.sysregs_loaded_on_cpu)
>> + goto memory_write;
>> +
>> + if (__vcpu_write_sys_reg_to_cpu(val, reg))
>> + return;
>> +
>> +memory_write:
>> __vcpu_sys_reg(vcpu, reg) = val;
>> }
>
> Again I think its clearer without the goto....
>
>
> Regardless:
> Reviewed-by: James Morse <james.morse@arm.com>

Thanks,

M.

[1]
https://git.kernel.org/pub/scm/linux/kernel/git/maz/arm-platforms.git/commit/?h=kvm-arm64/nv-5.7-rc1-WIP&id=11f3217d39a602cbfac7d08064c8b31afb57348e
--
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