linux-kernel - Re: [PATCH 1/2] KVM: async_pf: Cleanup kvm_setup_async

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Date:   Thu, 11 Jun 2020 10:31:08 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Sean Christopherson <sean.j.christopherson@...el.com>
Cc:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Vivek Goyal <vgoyal@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] KVM: async_pf: Cleanup kvm_setup_async_pf()

Sean Christopherson <sean.j.christopherson@...el.com> writes:

>
> I'd also be in favor of changing the return type to a boolean.  I think
> you alluded to it earlier, the current semantics are quite confusing as they
> invert the normal "return 0 on success".

Yes, will do a follow-up.

KVM/x86 code has an intertwined mix of:
- normal 'int' functions ('0 on success')
- bool functions ('true'/'1' on success)
- 'int' exit handlers ('1'/'0' on success depending if exit to userspace
  was required)
- ...

I think we can try to standardize this to:
- 'int' when error is propagated outside of KVM (userspace, other kernel
  subsystem,...)
- 'bool' when the function is internal to KVM and the result is binary
 ('is_exit_required()', 'was_pf_injected()', 'will_have_another_beer()',
 ...)
- 'enum' for the rest.
And, if there's a good reason for making an exception, require a
comment. (leaving aside everything returning a pointer, of course as
these are self-explanatory -- unless it's 'void *' :-))

>
> For this patch:
>
> Reviewed-by: Sean Christopherson <sean.j.christopherson@...el.com>
>

Thank you!

-- 
Vitaly